Publications by category
Journal articles
Grand-Clement E, Luscombe DJ, Anderson K, Gatis N, Benaud P, Brazier RE (In Press). Antecedent conditions control carbon loss and downstream water quality from shallow, damaged peatlands. Science of the Total Environment, 493, 961-973.
Forsmoo J, Anderson K, Macleod C, Wilkinson M, Brazier RE (In Press). Drone-based Structure-from-Motion photogrammetry captures grassland sward height variability. Journal of Applied Ecology
Gatis N, Anderson K, Grand-Clement E, Luscombe D, Hartley I, Smith D, Brazier R (In Press). Evaluating MODIS vegetation products using digital images for quantifying local peatland CO2 gas fluxes. Remote Sensing in Ecology and Conservation
Grand-Clement E, Anderson K, Smith D, Angus M, Luscombe D, Gatis N, Bray L, Brazier R (In Press). NEW APPROACHES TO THE RESTORATION OF SHALLOW MARGINAL PEATLANDS.
Journal of Environmental ManagementAbstract:
NEW APPROACHES TO THE RESTORATION OF SHALLOW MARGINAL PEATLANDS
Globally, the historic and recent exploitation of peatlands through management practices such as agricultural reclamation, peat harvesting or forestry, have caused extensive damage to these ecosystems. Their value is now increasingly recognised, and restoration and rehabilitation programmes are underway to improve some of the ecosystem services provided by peatlands: blocking drainage ditches in deep peat has been shown to improve the storage of water, decrease carbon losses in the long-term, and improve biodiversity. However, whilst the restoration process has benefitted from experience and technical advice gained from restoration of deep peatlands, shallow peatlands have received less attention in the literature, despite being extensive in both uplands and lowlands. Using the experience gained from the restoration of the shallow peatlands of Exmoor National Park (UK), and two test catchments in particular, this paper provides technical guidance which can be applied to the restoration of other shallow peatlands worldwide. Experience showed that integrating knowledge of the historical environment at the planning stage of restoration was essential, as it enabled the effective mitigation of any threat to archaeological features and sites. The use of bales, commonly employed in other upland ecosystems, was found to be problematic. Instead, ‘leaky dams’ or wood and peat combination dams were used, which are both more efficient at reducing and diverting the flow, and longer lasting than bale dams. Finally, an average restoration cost (£306 ha-1) for Exmoor, below the median national value across the whole of the UK, demonstrates the cost-effectiveness of these techniques. However, local differences in peat depth and ditch characteristics (i.e. length, depth and width) between sites affect both the feasibility and the cost of restoration. Overall, the restoration of shallow peatlands is shown to be technically viable; this paper provides a template for such process over analogous landscapes.
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Glendell M, Macshane G, Farrow L, Quinton J, Anderson K, Evans M, Benaud P, Rawlins B, Morgan D, Jones L, et al (In Press). Testing the utility of structure from motion photogrammetry reconstructions using small unmanned aerial vehicles and ground photography to estimate the extent of upland soil erosion. Earth Surface Processes and Landforms
Gatis N, Luscombe D, Grand-Clement E, Hartley I, Anderson K, Smith DM, Brazier RE (In Press). The effect of drainage ditches on vegetation diversity and CO2 fluxes in a Molinia caerulea dominated peatland. Ecohydrology
Bateman IJ, Anderson K, Argles A, Belcher C, Betts RA, Binner A, Brazier RE, Cho FHT, Collins RM, Day BH, et al (2023). A review of planting principles to identify the right place for the right tree for ‘net zero plus’ woodlands: Applying a place-based natural capital framework for sustainable, efficient and equitable (SEE) decisions.
People and Nature,
5(2), 271-301.
Abstract:
A review of planting principles to identify the right place for the right tree for ‘net zero plus’ woodlands: Applying a place-based natural capital framework for sustainable, efficient and equitable (SEE) decisions
We outline the principles of the natural capital approach to decision making and apply these to the contemporary challenge of very significantly expanding woodlands as contribution to attaining net zero emissions of greenhouse gases. Drawing on the case of the UK, we argue that a single focus upon carbon storage alone is likely to overlook the other ‘net zero plus’ benefits which woodlands can deliver. A review of the literature considers the wide variety of potential benefits which woodlands can provide, together with costs such as foregone alternative land uses. We argue that decision making must consider all of these potential benefits and costs for the right locations to be planted with the right trees. The paper closes by reviewing the decision support systems necessary to incorporate this information into policy and decision making. Read the free Plain Language Summary for this article on the Journal blog.
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Auster RE, Puttock AK, Barr SW, Brazier RE (2023). Learning to live with reintroduced species: beaver management groups are an adaptive <i>process</i>.
Restoration Ecology,
31(5).
Abstract:
Learning to live with reintroduced species: beaver management groups are an adaptive process
In anthropogenic landscapes, wildlife reintroductions are likely to result in interactions between people and reintroduced species. People living in the vicinity may have little familiarity with the reintroduced species or associated management, so will need to learn to live with the species in a new state of “Renewed Coexistence.” in England, Eurasian beavers (Castor fiber) are being reintroduced and U.K. Government agencies are currently considering their national approach to reintroduction and management. Early indications are this will include requirement for “Beaver Management Groups” (BMGs) to engage with local stakeholders. This policy paper reports on qualitative research that captured lessons from the governance of two existing BMGs in Devon (south‐west England), drawing on both a prior study and new interview data. Through the analysis, we identified that BMGs are not a fixed structure, but an adaptive process. This consists of three stages (Formation, Functioning, and Future?), influenced by resource availability and national policy direction. We argue that, where they are used, Species‐specific Management Groups could provide a “front line” for the integration of reintroduced species into modern landscapes, but their role or remit could be scaled back over time and integrated into existing structures or partnerships to reduce pressure on limited resources, as knowledge of reintroduced species (such as beaver) grows and its presence becomes “normalized.” There must be sufficient flexibility in forthcoming policy to minimize constraint on the adaptive nature of BMGs and similar groups for other reintroduced species, if they are to facilitate a sustainable coexistence.
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Slade G, Fawcett D, Cunliffe AM, Brazier RE, Nyaupane K, Mauritz M, Vargas S, Anderson K (2023). Optical reflectance across spatial scales—an intercomparison of transect-based hyperspectral, drone, and satellite reflectance data for dry season rangeland. Journal of Unmanned Vehicle Systems (JUVS), 11, 1-20.
Gatis N, Benaud P, Anderson K, Ashe J, Grand-Clement E, Luscombe DJ, Puttock A, Brazier RE (2023). Peatland restoration increases water storage and attenuates downstream stormflow but does not guarantee an immediate reversal of long-term ecohydrological degradation.
Sci Rep,
13(1).
Abstract:
Peatland restoration increases water storage and attenuates downstream stormflow but does not guarantee an immediate reversal of long-term ecohydrological degradation.
Peatland restoration is experiencing a global upsurge as a tool to protect and provide various ecosystem services. As the range of peatland types being restored diversifies, do previous findings present overly optimistic restoration expectations? in an eroding and restored upland peatland we assessed short-term (0-4 year) effects of restoration on ecohydrological functions. Restoration significantly reduced discharge from the site, transforming peat pans into pools. These retained surface water over half the time and were deeper during wet periods than before. In the surrounding haggs water tables stabilised, as drawdown during dry conditions reduced, increasing the saturated peat thickness. Despite these changes, there were no effects on photosynthesis, ecosystem respiration or dissolved organic carbon loads leaving the site. Soil respiration did not decrease as water tables rose, but methane emissions were higher from rewet pools. Restoration has had a dramatic effect on hydrology, however, consequent changes in other ecosystem functions were not measured in the 4 years after restoration. Whilst restoration is crucial in halting the expansion of degraded peatland areas, it is vital that practitioners and policymakers advocating for restoration are realistic about the expected outcomes and timescales over which these outcomes may manifest.
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Puttock A, Newman M, Graham H, Elliott M, Chant J, Auster R, Brazier R (2023). Positive coexistence of water voles and beaver: water vole expansion in a beaver engineered wetland.
Luscombe DJ, Gatis N, Anderson K, Carless D, Brazier RE (2023). Rapid, repeatable landscape-scale mapping of tree, hedgerow, and woodland habitats (THaW), using airborne LiDAR and spaceborne SAR data.
Ecol Evol,
13(5).
Abstract:
Rapid, repeatable landscape-scale mapping of tree, hedgerow, and woodland habitats (THaW), using airborne LiDAR and spaceborne SAR data.
In the UK, tree, hedgerow, and woodland (THaW) habitats are key havens for biodiversity and support many related ecosystem services. The UK is entering a period of agricultural policy realignment with respect to natural capital and climate change, meaning that now is a critical time to evaluate the distribution, resilience, and dynamics of THaW habitats. The fine-grained nature of habitats like hedgerows necessitates mapping of these features at relatively fine spatial resolution-and freely available public archives of airborne laser scanning (LiDAR) data at 90%. It was also possible to combine LiDAR mapping data and Sentinel-1 SAR data to rapidly track canopy change through time (i.e. every 3 months) using, cloud-based processing via Google Earth Engine. The resultant toolkit is also provided as an open-access web app. The results highlight that whilst nearly 90% of the tallest trees (above 15 m) are captured within the National Forest Inventory (NFI) database only 50% of THaW with a canopy height range of 3-15 m are recorded. Current estimates of tree distribution neglect these finer-grained features (i.e. smaller or less contiguous THaW canopies), which we argue will account for a significant proportion of landscape THaW cover.
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Auster RE, Puttock A, Bradbury G, Brazier R (2023). Should individual animals be given names in wildlife reintroductions?.
People and Nature,
5(4), 1110-1118.
Abstract:
Should individual animals be given names in wildlife reintroductions?
Individual animals are often given names by humans. For example, names are attributed to domestic animals to acknowledge their closeness to people, some research studies use names to identify differences between individuals in a study group, or zoos often use names to tell stories that attract public or media attention. Publicly naming individual animals can provide opportunities in conservation, but there are also risks. In this perspective we exemplify such opportunities and risks in the context of wildlife reintroductions. We draw on examples and observations from our experience researching Eurasian beaver Castor fiber reintroduction in England, to encourage careful thinking before publicly attributing a name to an individual in reintroduction projects. Naming individuals in reintroduction can: be a low-cost engagement tool; help people relate to unfamiliar reintroduced species; encourage local ownership of reintroduction projects; enable an effective tool for communicating information about the species and ways to coexist; or support creative or cultural expression. Yet naming individuals in reintroduction could: risk misrepresentation of natural species characteristics; make it challenging to normalise the sense that the reintroduced species is a wild animal; unintentionally imply that humans have ownership or power over the animal; cause distraction from establishing viable populations due to focus on the individual; or result in human investment in individual animals, which may have influence on reintroduction outcomes if that animal later comes to harm or dies (naturally or otherwise). Synthesis and Applications. We argue there is more to the act of naming individuals than may first appear. If considering doing so, we call for careful thought about whether it is appropriate and how to go about it. While we intentionally refrain from concluding whether ‘to name or not to name’, we call for careful, informative, message framing that takes advantage of the opportunities and is prepared for future circumstances, when naming of individuals does take place. Read the free Plain Language Summary for this article on the Journal blog.
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Benaud P, Anderson K, James MR, Quine TA, Quinton JN, Brazier RE (2023). Structure-from-Motion Photogrammetry and Rare Earth Oxides can quantify diffuse and convergent soil loss and source apportionment. International Soil and Water Conservation Research, 11(4), 633-648.
Bradbury G, Puttock A, Coxon G, Clarke S, Brazier RE (2023). Testing a novel sonar-based approach for measuring water depth and monitoring sediment storage in beaver ponds.
RIVER RESEARCH AND APPLICATIONS,
39(2), 266-273.
Author URL.
Gatis N, Carless D, Luscombe DJ, Brazier RE, Anderson K (2022). An operational land cover and land cover change toolbox: processing open‐source data with open‐source software.
Ecological Solutions and Evidence,
3(3).
Abstract:
An operational land cover and land cover change toolbox: processing open‐source data with open‐source software
Abstract
Accurate and up‐to‐date land cover maps are vital for underpinning evidence‐based landscape management decision‐making. However, the technical skills required to extract tailored information about land cover dynamics from these open‐access geospatial data often limit their use by those making landscape management decisions.
Using Dartmoor National Park as an example, we demonstrate an open‐source toolkit which uses open‐source software (QGIS and RStudio) to process freely available Sentinel‐2 and public LiDAR data sets to produce fine scale (10 m2 grain size) land cover maps.
The toolbox has been designed for use by staff within the national park, for example, enabling land cover maps to be updated as required in the future.
An area of 945 km2 was mapped using a trained random forest classifier following a classification scheme tailored to the needs of the national park.
A 2019 land cover map had an overall user's accuracy of 79%, with 13 out of 17 land cover classes achieving greater than 70% accuracy.
Spatially, accuracy was related via logistical regression to blue band surface reflectance in the spring and topographic slope derived from LiDAR (1 m resolution), with greater accuracy in steeper terrain and areas exhibiting higher blue reflectance.
Between an earlier (2017–2019) and later (2019–2021) time frame, 8% of pixels changed, most of the change by area occurred in the most common classes. However, the largest proportional increase occurred in Upland Meadows, Lowland Meadows and Blanket Bog, all habitats subject to restoration efforts. Identifying areas of change enables future field work to be better targeted.
We discuss the application of this mapping to land management within the Dartmoor national park and of the potential of tailored land cover and land cover change mapping, via this toolbox, to evidence‐based environmental decision‐making more widely.
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Fawcett D, Cunliffe AM, Sitch S, O’Sullivan M, Anderson K, Brazier RE, Hill TC, Anthoni P, Arneth A, Arora VK, et al (2022). Assessing Model Predictions of Carbon Dynamics in Global Drylands.
Frontiers in Environmental Science,
10Abstract:
Assessing Model Predictions of Carbon Dynamics in Global Drylands
Drylands cover ca. 40% of the land surface and are hypothesised to play a major role in the global carbon cycle, controlling both long-term trends and interannual variation. These insights originate from land surface models (LSMs) that have not been extensively calibrated and evaluated for water-limited ecosystems. We need to learn more about dryland carbon dynamics, particularly as the transitory response and rapid turnover rates of semi-arid systems may limit their function as a carbon sink over multi-decadal scales. We quantified aboveground biomass carbon (AGC; inferred from SMOS L-band vegetation optical depth) and gross primary productivity (GPP; from PML-v2 inferred from MODIS observations) and tested their spatial and temporal correspondence with estimates from the TRENDY ensemble of LSMs. We found strong correspondence in GPP between LSMs and PML-v2 both in spatial patterns (Pearson’s r = 0.9 for TRENDY-mean) and in inter-annual variability, but not in trends. Conversely, for AGC we found lesser correspondence in space (Pearson’s r = 0.75 for TRENDY-mean, strong biases for individual models) and in the magnitude of inter-annual variability compared to satellite retrievals. These disagreements likely arise from limited representation of ecosystem responses to plant water availability, fire, and photodegradation that drive dryland carbon dynamics. We assessed inter-model agreement and drivers of long-term change in carbon stocks over centennial timescales. This analysis suggested that the simulated trend of increasing carbon stocks in drylands is in soils and primarily driven by increased productivity due to CO2 enrichment. However, there is limited empirical evidence of this 50-year sink in dryland soils. Our findings highlight important uncertainties in simulations of dryland ecosystems by current LSMs, suggesting a need for continued model refinements and for greater caution when interpreting LSM estimates with regards to current and future carbon dynamics in drylands and by extension the global carbon cycle.
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Lockwood T, Freer J, Michaelides K, Brazier RE, Coxon G (2022). Assessing the efficacy of offline water storage ponds for natural flood management. Hydrological Processes, 36(6).
Auster RE, Barr SW, Brazier RE (2022). Beavers and flood alleviation: Human perspectives from downstream communities.
Journal of Flood Risk Management,
15(2).
Abstract:
Beavers and flood alleviation: Human perspectives from downstream communities
AbstractNatural flood management (NFM) methods work with natural processes to reduce flood risk, while often providing additional benefits such as water quality improvement or habitat provision. Increasingly, the activity of an animal—beavers—is recognised to potentially provide flow attenuation, along with multiple benefits for the environment and society, but there can also be associated challenges. We use Q‐Methodology to elicit and understand human perspectives of beavers and their potential role in flood management among communities living downstream of beavers at three sites in England (Cornwall, Yorkshire and the Forest of Dean). This is the first time a study has focused on downstream communities as the primary stakeholders. We identify diverse perspectives that exhibit a range of value judgements. We suggest a catchment‐based approach to beaver management and public engagement may facilitate deeper recognition of contextual perspectives in decision‐making and enable knowledge dissemination with communities. Further, we examine the relationship between beavers and other NFM methods through these perspectives. In doing so we identify features that relate to the unique element of relying on the natural behaviour of beavers for flood management, rather than human flood managers being the primary decision‐makers.
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Graham HA, Puttock AK, Elliott M, Anderson K, Brazier RE (2022). Exploring the dynamics of flow attenuation at a beaver dam sequence. Hydrological Processes, 36(11).
Cunliffe AM, Anderson K, Boschetti F, Brazier RE, Graham HA, Myers-Smith IH, Astor T, Boer MM, Calvo LG, Clark PE, et al (2022). Global application of an unoccupied aerial vehicle photogrammetry protocol for predicting aboveground biomass in non-forest ecosystems.
REMOTE SENSING IN ECOLOGY AND CONSERVATION,
8(1), 57-71.
Author URL.
Ritson JP, Kennedy-Blundell O, Croft J, Templeton MR, Hawkins CE, Clark JM, Evans MG, Brazier RE, Smith D, Graham NJD, et al (2022). High frequency UV-Vis sensors estimate error in riverine dissolved organic carbon load estimates from grab sampling.
Environ Monit Assess,
194(11).
Abstract:
High frequency UV-Vis sensors estimate error in riverine dissolved organic carbon load estimates from grab sampling.
High frequency ultraviolet - visible (UV-VIS) sensors offer a way of improving dissolved organic carbon (DOC) load estimates in rivers as they can be calibrated to DOC concentration. This is an improvement on periodic grab sampling, or the use of pumped sampling systems which store samples in-field before collection. We hypothesised that the move to high frequency measurements would increase the load estimate based on grab sampling due to systemic under-sampling of high flows. To test our hypotheses, we calibrated two sensors in contrasting catchments (Exe and Bow Brook, UK) against weekly grab sampled DOC measurements and then created an hourly time series of DOC for the two sites. Taking this measurement as a 'true' value of DOC load, we simulated 1,000 grab sampling campaigns at weekly, fortnightly and monthly frequency to understand the likely distribution of load and error estimates. We also performed an analysis of daily grab samples collected using a pumped storage sampling system with weekly collection. Our results show that: a) grab sampling systemically underestimates DOC loads and gives positively skewed distributions of results, b) this under-estimation and positive skew decreases with increasing sampling frequency, c) commonly used estimates of error in the load value are also systemically lowered by the oversampling of low, stable flows due to their dependence on the variance in the flow-weighted mean concentration, and d) that pumped storage systems may lead to under-estimation of DOC and over estimation of specific ultra-violet absorbance (SUVA), a proxy for aromaticity, due to biodegradation during storage.
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Graham HA, Puttock A, Chant J, Elliott M, Campbell‐Palmer R, Anderson K, Brazier RE (2022). Monitoring, modelling and managing beaver (Castor fiber) populations in the River Otter catchment, Great Britain. Ecological Solutions and Evidence, 3(3).
Auster RE, Barr SW, Brazier RE (2022). Renewed coexistence: learning from steering group stakeholders on a beaver reintroduction project in England.
EUROPEAN JOURNAL OF WILDLIFE RESEARCH,
68(1).
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Cunliffe AM, Boschetti F, Clement R, Sitch S, Anderson K, Duman T, Zhu S, Schlumpf M, Litvak ME, Brazier RE, et al (2022). Strong Correspondence in Evapotranspiration and Carbon Dioxide Fluxes Between Different Eddy Covariance Systems Enables Quantification of Landscape Heterogeneity in Dryland Fluxes. Journal of Geophysical Research Biogeosciences, 127(8).
Puttock A, Graham HA, Ashe J, Luscombe DJ, Brazier RE (2021). Beaver dams attenuate flow: a multi-site study.
Hydrological Processes,
35(2).
Abstract:
Beaver dams attenuate flow: a multi-site study
Beavers can profoundly alter riparian environments, most conspicuously by creating dams and wetlands. Eurasian beaver (Castor fiber) populations are increasing and it has been suggested they could play a role in the provision of multiple ecosystem services, including natural flood management. Research at different scales, in contrasting ecosystems is required to establish to what extent beavers can impact on flood regimes. Therefore, this study determines whether flow regimes and flow responses to storm events were altered following the building of beaver dams and whether a flow attenuation effect could be significantly attributed to beaver activity. Four sites were monitored where beavers have been reintroduced in England. Continuous monitoring of hydrology, before and after beaver impacts, was undertaken on streams where beavers built sequences of dams. Stream orders ranged from 2nd to 4th, in both agricultural and forest-dominated catchments. Analysis of >1000 storm events, across four sites showed an overall trend of reduced total stormflow, increased peak rainfall to peak flow lag times and reduced peak flows, all suggesting flow attenuation, following beaver impacts. Additionally, reduced high flow to low flow ratios indicated that flow regimes were overall becoming less “flashy” following beaver reintroduction. Statistical analysis, showed the effect of beaver to be statistically significant in reducing peak flows with estimated overall reductions in peak flows from −0.359 to −0.065 m3 s−1 across sites. Analysis showed spatial and temporal variability in the hydrological response to beaver between sites, depending on the level of impact and seasonality. Critically, the effect of beavers in reducing peak flows persists for the largest storms monitored, showing that even in wet conditions, beaver dams can attenuate average flood flows by up to ca. 60%. This research indicates that beavers could play a role in delivering natural flood management.
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Ellis N, Brazier R, Anderson K (2021). Comparing fine‐scale structural and hydrologic connectivity within unimproved and improved grassland.
Ecohydrology,
14(7).
Abstract:
Comparing fine‐scale structural and hydrologic connectivity within unimproved and improved grassland
AbstractGrasslands vary with diverse forms and functions ranging from monocultures of perennial rye grass to more biodiverse unimproved grasslands which cover around 5% of Europe. Despite the broad diversity of grassland types, within environmental and flood risk models grasslands are frequently represented by a singular set of hydrological and structural parameters which belies their diversity and complexity. This study aimed to determine empirically the extent to which improved versus unimproved grasslands exhibit different hydrological connectivity. Working in SW England at neighbouring field sites with comparable slopes and rainfall regimes, we used unpiloted aerial vehicles to survey a tussocky Molinia caerulea dominated unimproved grassland field (MCUG) field and a Lolium perenne dominated improved grassland (LPIG) field. Using digital photogrammetry workflows applied to the overlapping aerial images, we produced a digital surface model (DSM) at 0.03‐m resolution from which flow pathways were modelled using GIS and compared with 1‐m LiDAR and DSM produced by a global navigation satellite system (GNSS). MCUG had longer, tortuous pathways through the dense tussock network with a drainage density of 2.54 m m−2. This was significantly greater than drainage density in the LPIG (1.82 m m−2). As a result of this study, we rescaled the Manning's n value for MCUG according to photogrammetrically‐derived roughness values. We suggest it should lie between 0.075 and 0.09. Our data shows that MCUG can play an important role in reducing overland flow impacts when compared to LPIG through lower connectivity which can delay run‐off to rivers.
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Ellis N, Anderson K, Brazier R (2021). Mainstreaming natural flood management: a proposed research framework derived from a critical evaluation of current knowledge.
Progress in Physical Geography: Earth and Environment,
45(6), 819-841.
Abstract:
Mainstreaming natural flood management: a proposed research framework derived from a critical evaluation of current knowledge
Natural flood management (NFM), or working with natural processes, is a growing flood risk management method in the UK, Europe and worldwide. However, unlike the current dominant technical flood management, it lacks an established evidence base of flood risk parameters. This lack of evidence base can limit the uptake of NFM as a flood management method. This paper critically evaluates examples of NFM and wider relevant literature in order to identify NFM knowledge gaps and suggest how to overcome these. The UK is used as a microcosm of different environments for diverse examples. The sections include: land cover, land management, landscape interactions and trade-offs, evaluating the wider benefits of NFM and, finally, scaling from plot to catchment. This concludes in a suggested framework for a new approach to NFM research, which encompasses spatial scales, interactions and trade-offs of NFM and consistency of reporting results. Widening the NFM empirical evidence base should be seen as an opportunity for a new approach to flood research through exploring new habitats and new flood resilience methods.
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Campbell-Palmer R, Puttock A, Wilson KA, Leow-Dyke A, Graham HA, Gaywood MJ, Brazier RE (2021). Using field sign surveys to estimate spatial distribution and territory dynamics following reintroduction of the Eurasian beaver to British river catchments.
RIVER RESEARCH AND APPLICATIONS,
37(3), 343-357.
Author URL.
Cunliffe AM, McIntire CD, Boschetti F, Sauer KJ, Litvak M, Anderson K, Brazier RE (2020). Allometric Relationships for Predicting Aboveground Biomass and Sapwood Area of Oneseed Juniper (Juniperus monosperma) Trees.
Frontiers in Plant Science,
11Abstract:
Allometric Relationships for Predicting Aboveground Biomass and Sapwood Area of Oneseed Juniper (Juniperus monosperma) Trees
Across the semi-arid ecosystems of the southwestern USA, there has been widespread encroachment of woody shrubs and trees including Juniperus species into former grasslands. Quantifying vegetation biomass in such ecosystems is important because semi-arid ecosystems are thought to play an important role in the global land carbon (C) sink, and changes in plant biomass also have implications for primary consumers and potential bioenergy feedstock. Oneseed Juniper (J. monosperma) is common in desert grasslands and pinyon-juniper rangelands across the intermountain region of southwestern North America; however, there is limited information about the aboveground biomass (AGB) and sapwood area (SWA) for this species, causing uncertainties in estimates of C stock and transpiration fluxes. In this study, we report on canopy area, stem diameter, maximum height and biomass measurements from J. monosperma trees sampled from central New Mexico. Dry biomass ranged between 0.4 kg and 625 kg, and cross-sectional sapwood area was measured on n=200 stems using image analysis. We found a strong linear relationship between canopy area and AGB (r2 = 0.96), with a similar slope to that observed in other juniper species, suggesting that this readily measured attribute is well suited for upscaling studies. There was a 9% bias between different approaches to measuring canopy area, indicating care should be taken to account for these differences to avoid systematic biases. We found equivalent stem diameter (ESD) was a strong predictor of biomass, but that existing allometric models under-predicted biomass in larger trees. We found sapwood area could be predicted from individual stem diameter with a power relationship, and that tree-level SWA should be estimated by summing the SWA predictions from individual stems rather than ESD. Our improved allometric models for J. monosperma support more accurate and robust measurements of C storage and transpiration fluxes in Juniperus-dominated ecosystems.
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Auster RE, Barr S, Brazier R (2020). Alternative perspectives of the angling community on Eurasian beaver (<i>Castor fiber</i>) reintroduction in the River Otter Beaver Trial. Journal of Environmental Planning and Management, 64(7), 1252-1270.
Brazier RE, Puttock A, Graham HA, Auster RE, Davies KH, Brown CML (2020). Beaver: Nature's ecosystem engineers.
WIREs Water,
8(1).
Abstract:
Beaver: Nature's ecosystem engineers
AbstractBeavers have the ability to modify ecosystems profoundly to meet their ecological needs, with significant associated hydrological, geomorphological, ecological, and societal impacts. To bring together understanding of the role that beavers may play in the management of water resources, freshwater, and terrestrial ecosystems, this article reviews the state‐of‐the‐art scientific understanding of the beaver as the quintessential ecosystem engineer. This review has a European focus but examines key research considering both Castor fiber—the Eurasian beaver and Castor canadensis—its North American counterpart. In recent decades species reintroductions across Europe, concurrent with natural expansion of refugia populations has led to the return of C. fiber to much of its European range with recent reviews estimating that the C. fiber population in Europe numbers over 1.5 million individuals. As such, there is an increasing need for understanding of the impacts of beaver in intensively populated and managed, contemporary European landscapes. This review summarizes how beaver impact: (a) ecosystem structure and geomorphology, (b) hydrology and water resources, (c) water quality, (d) freshwater ecology, and (e) humans and society. It concludes by examining future considerations that may need to be resolved as beavers further expand in the northern hemisphere with an emphasis upon the ecosystem services that they can provide and the associated management that will be necessary to maximize the benefits and minimize conflicts.This article is categorized under:
Water and Life > Nature of Freshwater Ecosystems
Abstract.
Gatis N, Luscombe DJ, Benaud P, Ashe J, Grand-Clement E, Anderson K, Hartley IP, Brazier RE (2020). Drain blocking has limited short-term effects on greenhouse gas fluxes in a Molinia caerulea dominated shallow peatland. Ecological Engineering, 158, 106079-106079.
Cunliffe AM, Anderson K, Boschetti F, Brazier RE, Graham HA, Myers-Smith IH, Astor T, Boer MM, Calvo L, Clark PE, et al (2020). Drone-derived canopy height predicts biomass across non-forest ecosystems globally.
Abstract:
Drone-derived canopy height predicts biomass across non-forest ecosystems globally
AbstractNon-forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, yet are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely-sensed biomass products and are undersampled by in-situ monitoring. Current global change threats emphasise the need for new tools to capture biomass change in non-forest ecosystems at appropriate scales. Here we assess whether canopy height inferred from drone photogrammetry allows the estimation of aboveground biomass (AGB) across low-stature plant species sampled through a global site network. We found mean canopy height is strongly predictive of AGB across species, demonstrating standardised photogrammetric approaches are generalisable across growth forms and environmental settings. Biomass per-unit-of-height was similar within, but different among, plant functional types. We find drone-based photogrammetry allows for monitoring of AGB across large spatial extents and can advance understanding of understudied and vulnerable non-forested ecosystems across the globe.
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Auster RE, Barr SW, Brazier RE (2020). Improving engagement in managing reintroduction conflicts: learning from beaver reintroduction. Journal of Environmental Planning and Management, 64(10), 1713-1734.
Graham HA, Puttock A, Macfarlane WW, Wheaton JM, Gilbert JT, Campbell-Palmer R, Elliott M, Gaywood MJ, Anderson K, Brazier RE, et al (2020). Modelling Eurasian beaver foraging habitat and dam suitability, for predicting the location and number of dams throughout catchments in Great Britain.
European Journal of Wildlife Research,
66(3).
Abstract:
Modelling Eurasian beaver foraging habitat and dam suitability, for predicting the location and number of dams throughout catchments in Great Britain
AbstractEurasian beaver (Castor fiber) populations are expanding across Europe. Depending on location, beaver dams bring multiple benefits and/or require management. Using nationally available data, we developed: a Beaver Forage Index (BFI), identifying beaver foraging habitat, and a Beaver Dam Capacity (BDC) model, classifying suitability of river reaches for dam construction, to estimate location and number of dams at catchment scales. Models were executed across three catchments, in Great Britain (GB), containing beaver. An area of 6747 km2 was analysed for BFI and 16,739 km of stream for BDC. Field surveys identified 258 km of channel containing beaver activity and 89 dams, providing data to test predictions. Models were evaluated using a categorical binomial Bayesian framework to calculate probability of foraging and dam construction. BFI and BDC models successfully categorised the use of reaches for foraging and damming, with higher scoring reaches being preferred. Highest scoring categories were ca. 31 and 79 times more likely to be used than the lowest for foraging and damming respectively. Zero-inflated negative binomial regression showed that modelled dam capacity was significantly related (p = 0.01) to observed damming and was used to predict numbers of dams that may occur. Estimated densities of dams, averaged across each catchment, ranged from 0.4 to 1.6 dams/km, though local densities may be up to 30 dams/km. These models provide fundamental information describing the distribution of beaver foraging habitat, where dams may be constructed and how many may occur. This supports the development of policy and management concerning the reintroduction and recolonisation of beaver.
Abstract.
Benaud P, Anderson K, Evans M, Farrow L, Glendell M, James MR, Quine TA, Quinton JN, Rawlins B, Jane Rickson R, et al (2020). National-scale geodata describe widespread accelerated soil erosion.
Geoderma,
371Abstract:
National-scale geodata describe widespread accelerated soil erosion
Accelerated soil erosion can result in substantial declines in soil fertility and has devastating environmental impacts. Consequently, understanding if rates of soil erosion are acceptable is of local and global importance. Herein we use empirical soil erosion observations collated into an open access geodatabase to identify the extent to which existing data and methodological approaches can be used to develop an empirically-derived understanding of soil erosion in the UK (by way of an example). The findings indicate that whilst mean erosion rates in the UK are low, relative to the rest of Europe for example, 16% of observations on arable land were greater than the supposedly tolerable rate of 1 t ha−1 yr−1 and maximum erosion rates were as high as 91.7 t ha−1 yr−1. However, the analysis highlights a skew in existing studies towards locations with a known erosion likelihood and methods that are biased towards single erosion pathways, rather than an all-inclusive study of erosion rates and processes. Accordingly, we suggest that future soil erosion research and policy must address these issues if an accurate assessment of soil erosion rates at the national-scale are to be established. The interactive geodatabase published alongside this paper offers a platform for the simultaneous development of soil erosion research, formulation of effective policy and better protection of soil resources.
Abstract.
Auster RE, Barr SW, Brazier RE (2020). Wildlife tourism in reintroduction projects: Exploring social and economic benefits of beaver in local settings. Journal for Nature Conservation, 58, 125920-125920.
Gatis N, Benaud P, Ashe J, Luscombe D, Grand-Clement E, Hartley I, Anderson K, Brazier R (2019). ASSESSING THE IMPACT OF PEAT EROSION ON GROWING SEASON CO2 FLUXES BY COMPARING EROSIONAL PEAT PANS AND SURROUNDING VEGETATED HAGGS.
Wetlands Ecology and Management, 1-19.
Abstract:
ASSESSING THE IMPACT OF PEAT EROSION ON GROWING SEASON CO2 FLUXES BY COMPARING EROSIONAL PEAT PANS AND SURROUNDING VEGETATED HAGGS
Peatlands are recognised as an important but vulnerable ecological resource. Understanding the effects of existing damage, in this case erosion, enables more informed land management decisions to be made. Over the growing seasons of 2013 and 2014 photosynthesis and ecosystem respiration were measured using closed chamber techniques within vegetated haggs and erosional peat pans in Dartmoor National Park, southwest England. Below-ground total and heterotrophic respiration were measured and autotrophic respiration estimated from the vegetated haggs.
The mean water table was significantly higher in the peat pans than in the vegetated haggs; because of this, and the switching from submerged to dry peat, there were differences in vegetation composition, photosynthesis and ecosystem respiration. In the peat pans photosynthetic CO2 uptake and ecosystem respiration were greater than in the vegetated haggs and strongly dependent on the depth to water table (r2>0.78, p
Abstract.
Gatis N, Grand-Clement E, Luscombe DJ, Hartley IP, Anderson K, Brazier RE (2019). Growing season CO<sub>2</sub> fluxes from a drained peatland dominated by <i>Molinia caerulea</i>.
MIRES AND PEAT,
24 Author URL.
Carless D, Luscombe DJ, Gatis N, Anderson K, Brazier RE (2019). Mapping landscape-scale peatland degradation using airborne lidar and multispectral data. Landscape Ecology, 34, 1329-1345.
Ritson JP, Croft JK, Clark JM, Brazier RE, Templeton MR, Smith D, Graham NJD (2019). Sources of dissolved organic carbon (DOC) in a mixed land use catchment (Exe, UK).
Science of the Total Environment,
666, 165-175.
Abstract:
Sources of dissolved organic carbon (DOC) in a mixed land use catchment (Exe, UK)
Many catchment management schemes in the UK have focussed on peatland restoration to improve ecosystem services such as carbon sequestration, water quality and biodiversity. The effect of these schemes on dissolved organic carbon (DOC) flux is critical in understanding peatland carbon budgets as well as the implications for drinking water treatment. In many catchments, however, peatland areas are not the only source of DOC, meaning that their significance at the full catchment scale is unclear. In this paper we have evaluated the importance of different land uses as sources of DOC by combining three datasets obtained from the Exe catchment, UK. The first dataset comprises a weekly monitoring record at three sites for six years, the second, a monthly monitoring record of 25 sites in the same catchment for one year, and the third, an assessment of DOC export from litter and soil carbon stocks. Our results suggest that DOC concentration significantly increased from the peaty headwaters to the mixed land-use areas (ANOVA F = 12.52, p < 0.001, df = 2), leading to higher flux estimates at the downstream sites. We present evidence for three possible explanations: firstly, that poor sampling of high flows may lead to underestimation of DOC flux, second, that there are significant sources of DOC besides the peatland headwaters, and finally, that biological- and photo-degradation decreases the influence of upstream DOC sources. Our results provide evidence both for the targeting of catchment management in peatland areas as well as the need to consider DOC from agricultural and forested areas of the catchment.
Abstract.
Forsmoo J, Anderson K, Macleod CJA, Wilkinson ME, DeBell L, Brazier RE (2019). Structure from motion photogrammetry in ecology: Does the choice of software matter?.
Ecology and Evolution,
9(23), 12964-12979.
Abstract:
Structure from motion photogrammetry in ecology: Does the choice of software matter?
AbstractImage‐based modeling, and more precisely, Structure from Motion (SfM) and Multi‐View Stereo (MVS), is emerging as a flexible, self‐service, remote sensing tool for generating fine‐grained digital surface models (DSMs) in the Earth sciences and ecology. However, drone‐based SfM + MVS applications have developed at a rapid pace over the past decade and there are now many software options available for data processing. Consequently, understanding of reproducibility issues caused by variations in software choice and their influence on data quality is relatively poorly understood. This understanding is crucial for the development of SfM + MVS if it is to fulfill a role as a new quantitative remote sensing tool to inform management frameworks and species conservation schemes. To address this knowledge gap, a lightweight multirotor drone carrying a Ricoh GR II consumer‐grade camera was used to capture replicate, centimeter‐resolution image datasets of a temperate, intensively managed grassland ecosystem. These data allowed the exploration of method reproducibility and the impact of SfM + MVS software choice on derived vegetation canopy height measurement accuracy. The quality of DSM height measurements derived from four different, yet widely used SfM‐MVS software—Photoscan, Pix4D, 3DFlow Zephyr, and MICMAC, was compared with in situ data captured on the same day as image capture. We used both traditional agronomic techniques for measuring sward height, and a high accuracy and precision differential GPS survey to generate independent measurements of the underlying ground surface elevation. Using the same replicate image dataset (n = 3) as input, we demonstrate that there are 1.7, 2.0, and 2.5 cm differences in RMSE (excluding one outlier) between the outputs from different SfM + MVS software using High, Medium, and Low quality settings, respectively. Furthermore, we show that there can be a significant difference, although of small overall magnitude between replicate image datasets (n = 3) processed using the same SfM + MVS software, following the same workflow, with a variance in RMSE of up to 1.3, 1.5, and 2.7 cm (excluding one outlier) for “High,” “Medium,” and “Low” quality settings, respectively. We conclude that SfM + MVS software choice does matter, although the differences between products processed using “High” and “Medium” quality settings are of small overall magnitude.
Abstract.
Auster R, Puttock A, Brazier R (2019). Unravelling perceptions of Eurasian beaver reintroduction in Great Britain. AREA
Brazier RE, humphries RN (2018). Exploring the case for a national-scale soil conservation and soil condition 1 framework for evaluating and reporting on environmental and land use 2 policies. Soil Use and Management
Gatis N, Luscombe D, Carless D, Parry L, Fyfe R, Harrod T, Brazier RE, Anderson K (2018). Mapping upland peat depth using airborne radiometric and lidar survey data.
Geoderma,
335, 78-89.
Abstract:
Mapping upland peat depth using airborne radiometric and lidar survey data
A method to estimate peat depth and extent is vital for accurate estimation of carbon stocks and to facilitate appropriate peatland management. Current methods for direct measurement (e.g. ground penetrating radar, probing) are labour intensive making them unfeasible for capturing spatial information at landscape extents. Attempts to model peat depths using remotely sensed data such as elevation and slope have shown promise but assume a functional relationship between current conditions and gradually accrued peat depth. Herein we combine LiDAR-derived metrics known to influence peat accumulation (elevation, slope, topographic wetness index (TWI)) with passive gamma-ray spectrometric survey data, shown to correlate with peat occurrence to develop a novel peat depth model for Dartmoor.
Total air absorbed dose rates of Thorium, Uranium and Potassium were calculated, referred to as radiometric dose. Relationships between peat depth, radiometric dose, elevation, slope and TWI were trained using 1334 peat depth measurements, a further 445 measurements were used for testing. All variables showed significant relationships with peat depth. Linear stepwise regression of natural log-transformed variables indicated that a radiometric dose and slope model had an r2 = 0.72/0.73 and RMSE 0.31/0.31 m for training/testing respectively. This model estimated an area of 158 ±101 km2 of peaty soil >0.4 m deep across the study area. Much of this area (60 km2) is overlain by grassland and therefore may have been missed if vegetation cover was used to map peat extent. Using published bulk density and carbon content values we estimated 13.1 Mt C (8.1-21.9 Mt C) are stored in the peaty soils within the study area. This is an increase on previous estimates due to greater modelled peat depth. The combined use of airborne gamma-ray spectrometric survey and LiDAR data provide a novel, practical and repeatable means to estimate peat depth with no a priori knowledge, at an appropriate resolution (10 m) and extent (406 km2) to facilitate management of entire peatland complexes.
Abstract.
Brown AG, Lespez L, Sear DA, Macaire JJ, Houben P, Klimek K, Brazier RE, Van Oost K, Pears B (2018). Natural vs anthropogenic streams in Europe: History, ecology and implications for restoration, river-rewilding and riverine ecosystem services.
Earth-Science Reviews,
180, 185-205.
Abstract:
Natural vs anthropogenic streams in Europe: History, ecology and implications for restoration, river-rewilding and riverine ecosystem services
In Europe and North America the prevailing model of “natural” lowland streams is incised-meandering channels with silt-clay floodplains, and this is the typical template for stream restoration. Using both published and new unpublished geological and historical data from Europe we critically review this model, show how it is inappropriate for the European context, and examine the implications for carbon sequestration and Riverine Ecosystem Services (RES) including river rewilding. This paper brings together for the first time, all the pertinent strands of evidence we now have on the long-term trajectories of floodplain system from sediment-based dating to sedaDNA. Floodplain chronostratigraphy shows that early Holocene streams were predominantly multi-channel (anabranching) systems, often choked with vegetation and relatively rarely single-channel actively meandering systems. Floodplains were either non-existent or limited to adjacent organic-filled palaeochannels, spring/valley mires and flushes. This applied to many, if not most, small to medium rivers but also major sections of the larger rivers such as the Thames, Seine, Rhône, Lower Rhine, Vistula and Danube. As shown by radiocarbon and optically stimulated luminescence (OSL) dating during the mid-late Holocene c. 4–2 ka BP, overbank silt-clay deposition transformed European floodplains, covering former wetlands and silting-up secondary channels. This was followed by direct intervention in the Medieval period incorporating weir and mill-based systems – part of a deep engagement with rivers and floodplains which is even reflected in river and floodplain settlement place names. The final transformation was the “industrialisation of channels” through hard-engineering – part of the Anthropocene great acceleration. The primary causative factor in transforming pristine floodplains was accelerated soil erosion caused by deforestation and arable farming, but with effective sediment delivery also reflecting climatic fluctuations. Later floodplain modifications built on these transformed floodplain topographies. So, unlike North America where channel-floodplain transformation was rapid, the transformation of European streams occurred over a much longer time-period with considerable spatial diversity regarding timing and kind of modification. This has had implications for the evolution of RES including reduced carbon sequestration over the past millennia. Due to the multi-faceted combination of catchment controls, ecological change and cultural legacy, it is impractical, if not impossible, to identify an originally natural condition and thus restore European rivers to their pre-transformation state (naturalisation). Nevertheless, attempts to restore to historical (pre-industrial) states allowing for natural floodplain processes can have both ecological and carbon offset benefits, as well as additional abiotic benefits such as flood attenuation and water quality improvements. This includes rewilding using beaver reintroduction which has overall positive benefits on river corridor ecology. New developments, particularly biomolecular methods offer the potential of unifying modern ecological monitoring with the reconstruction of past ecosystems and their trajectories. The sustainable restoration of rivers and floodplains designed to maximise desirable RES and natural capital must be predicated on the awareness that Anthropocene rivers are still largely imprisoned in the banks of their history and this requires acceptance of an increased complexity for the achievement and maintenance of desirable restoration goals.
Abstract.
Puttock A, Brazier R, Graham H, Carless D (2018). Sediment and nutrient storage in a beaver engineered wetland. Earth Surface Processes and Landforms
Bell MC, Ritson JP, Verhoef A, Brazier RE, Templeton MR, Graham NJD, Freeman C, Clark JM (2018). Sensitivity of peatland litter decomposition to changes in temperature and rainfall.
Geoderma,
331, 29-37.
Abstract:
Sensitivity of peatland litter decomposition to changes in temperature and rainfall
Changes to climate are projected over the next 50 years for many peatland areas. As decomposition of peat-forming vegetation is likely to be intrinsically linked to these changes in climate, a clear understanding of climate-peat dynamics is required. There is concern that increased temperature and decreased precipitation could increase the rate of decomposition and put the carbon sink status of many peatlands at risk, yet few studies have examined the impact of both climatic factors together. To better understand the sensitivity of peatland decomposition to changes in both temperature and precipitation and their interaction, we conducted a short-term laboratory experiment in which plant litters and peat soil were incubated, in isolation, in a factorial design. Treatments simulated baseline and projected climate averages derived from the latest UK climate change projections (UKCP09) for Exmoor, a climatically marginal peatland in SW England. Regular carbon dioxide flux measurements were made throughout the simulation, as well as total mass loss and total dissolved organic carbon (DOC) leached. The largest effect on carbon loss in this multifactor experiment was from substrate, with Sphagnum/peat releasing significantly less C in total during the experiment than dwarf shrubs/graminoids. Climate effects were substrate specific, with the drier rainfall treatment increasing the DOC leaching from Calluna, but decreasing it from Sphagnum. Partitioning between CO2 and DOC was also affected by climate, but only for the peat and Sphagnum samples, where the future climate scenarios (warmer and drier) resulted in a greater proportion of C lost in gaseous form. These results suggest that indirect effects of climate through changes in species composition in peatlands could ultimately turn out to be more important for litter decomposition than direct effects of climate change from increased temperatures and decreased rainfall.
Abstract.
Eludoyin AO, Griffith B, Orr RJ, Bol R, Quine TA, Brazier RE (2017). An evaluation of the hysteresis in chemical concentration–discharge (C–Q) relationships from drained, intensively managed grasslands in southwest England.
Hydrological Sciences Journal,
62(8), 1243-1254.
Abstract:
An evaluation of the hysteresis in chemical concentration–discharge (C–Q) relationships from drained, intensively managed grasslands in southwest England
This study examined the hysteresis exhibited in concentration–discharge (C–Q) relationships in the runoff from four hydrologically separated fields (catchments) at an intensively managed grassland. The objectives were to examine C–Q relationships constructed from high-resolution time series of flow, temperature, pH, conductivity, nitrate and turbidity, and their implications for hydrological processes. High-resolution datasets from the quality assured records of the Rothamsted Research North Wyke Farm Platform in the UK were examined using a graphical method and cross-correlation statistics. The study found that storm events based C–Q hysteresis reflects the cross-correlation that is generally hidden in time series analysis of large datasets, and that although Q and water quality variables can be effectively influenced by catchment size, the C–Q relationship is less significantly influenced. The dominant C–Q relationships of the water variables in the study area reflect that saturated overland flow was prevalent during the study period in the catchments, while the CCF results indicate coupled transfer of sediments and solute in the area at lag ≥ 0. EDITOR D. Koutsoyiannis ASSOCIATE EDITOR M. D. Fidelibus.
Abstract.
Turley MD, Bilotta GS, Arbociute G, Chadd RP, Extence CA, Brazier RE (2017). Quantifying Submerged Deposited Fine Sediments in Rivers and Streams Using Digital Image Analysis.
River Research and Applications,
33(10), 1585-1595.
Abstract:
Quantifying Submerged Deposited Fine Sediments in Rivers and Streams Using Digital Image Analysis
Deposited fine sediment is an essential component of freshwater ecosystems. Nonetheless, anthropogenic activities can modify natural fine sediment levels, impacting the physical, chemical and biological characteristics of these ecosystems. An ability to quantify deposited fine sediment is critical to understanding its impacts and successfully managing the anthropogenic activities that are responsible for modifying it. One widely used method, the visual estimate technique, relies on subjective estimates of particle size and percentage cover. In this paper, we present two novel alternative approaches, based on non-automated digital image analysis (DIA), which are designed to reduce the subjectivity of submerged and surficial fine sediment estimates, and provide a verifiable record of the conditions at the time of sampling. The DIA methods were tested across five systematically selected, contrasting temperate stream and river typologies, over three seasons of monitoring. The resultant sediment metrics were strongly, positively correlated with visual estimates (rs = 0.90, and rs = 0.82, p < 0.01), and similarly strongly, but negatively correlated with a sediment-specific biotic index, suggesting some degree of biological relevance. The DIA technique has the potential to be a valuable tool for application in numerous areas of river research, where a non-destructive, less subjective and verifiable method is desirable. Copyright ©2016 the Authors River Research and Applications Published by John Wiley & Sons Ltd.
Abstract.
Ritson JP, Brazier RE, Graham NJD, Freeman C, Templeton MR, Clark JM (2017). The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources.
Biogeosciences,
14(11), 2891-2902.
Abstract:
The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources
Drought conditions are expected to increase in frequency and severity as the climate changes, representing a threat to carbon sequestered in peat soils. Downstream water treatment works are also at risk of regulatory compliance failures and higher treatment costs due to the increase in riverine dissolved organic carbon (DOC) often observed after droughts. More frequent droughts may also shift dominant vegetation in peatlands from Sphagnum moss to more drought-tolerant species. This paper examines the impact of drought on the production and treatability of DOC from four vegetation litters (Calluna vulgaris, Juncus effusus, Molinia caerulea and Sphagnum spp.) and a peat soil. We found that mild droughts caused a 39.6% increase in DOC production from peat and that peat DOC that had been exposed to oxygen was harder to remove by conventional water treatment processes (coagulation/flocculation). Drought had no effect on the amount of DOC production from vegetation litters; however large variation was observed between typical peatland species (Sphagnum and Calluna) and drought-tolerant grassland species (Juncus and Molinia), with the latter producing more DOC per unit weight. This would therefore suggest the increase in riverine DOC often observed post-drought is due entirely to soil microbial processes and DOC solubility rather than litter layer effects. Long-term shifts in species diversity may, therefore, be the most important impact of drought on litter layer DOC flux, whereas pulses related to drought may be observed in peat soils and are likely to become more common in the future. These results provide evidence in support of catchment management which increases the resilience of peat soils to drought, such as ditch blocking to raise water tables.
Abstract.
Turley MD, Bilotta GS, Chadd RP, Extence CA, Brazier RE, Burnside NG, Pickwell AGG (2016). A sediment-specific family-level biomonitoring tool to identify the impacts of fine sediment in temperate rivers and streams.
Ecological Indicators,
70, 151-165.
Abstract:
A sediment-specific family-level biomonitoring tool to identify the impacts of fine sediment in temperate rivers and streams
Anthropogenic modifications of sediment load can cause ecological degradation in stream and river ecosystems. However, in practice, identifying when and where sediment is the primary cause of ecological degradation is a challenging task. Biological communities undergo natural cycles and variation over time, and respond to a range of physical, chemical and biological pressures. Furthermore, fine sediments are commonly associated with numerous other pressures that are likely to influence aquatic biota. The use of conventional, non-biological monitoring to attribute cause and effect would necessitate measurement of multiple parameters, at sufficient temporal resolution, and for a significant period of time. Biomonitoring tools, which use low-frequency measurements of biota to gauge and track changes in the environment, can provide a valuable alternative means to detecting the effects of a given pressure. In this study, we develop and test an improved macroinvertebrate, family-level and mixed-level biomonitoring tool for fine sediment. Biologically-based classifications of sediment sensitivity were supplemented by using empirical data of macroinvertebrate abundance and percentage fine sediment, collected across a wide range of temperate river and stream ecosystems (model training dataset n = 2252) to assign detailed individual sensitivity weights to taxa. An optimum set of weights were identified by non-linear optimisation, as those that resulted in the highest Spearman's rank correlation coefficient between the index (called the Empirically-weighted Proportion of Sediment-sensitive Invertebrates index; E-PSI) scores and deposited fine sediment in the model training dataset. The family and mixed-level tools performed similarly, with correlations with percentage fine sediment in the test dataset (n = 84) of rs = -0.72 and rs = -0.70 p < 0.01. Testing of the best performing family level version, over agriculturally impacted sites (n = 754) showed similar correlations to fine sediment (rs = -0.68 p < 0.01). The tools developed in this study have retained their biological basis, are easily integrated into contemporary monitoring agency protocols and can be applied retrospectively to historic datasets. Given the challenges of non-biological conventional monitoring of fine sediments and determining the biological relevance of the resulting data, a sediment-specific biomonitoring approach is highly desirable and will be a useful addition to the suite of pressure-specific biomonitoring tools currently used to infer the causes of ecological degradation.
Abstract.
Cunliffe AM, Puttock AK, Turnbull L, Wainwright J, Brazier RE (2016). Dryland, calcareous soils store (and lose) significant quantities of near-surface organic carbon.
Journal of Geophysical Research: Earth Surface,
121(4), 684-702.
Abstract:
Dryland, calcareous soils store (and lose) significant quantities of near-surface organic carbon
©2016. The Authors. Semiarid ecosystems are susceptible to changes in dominant vegetation which may have significant implications for terrestrial carbon dynamics. The present study examines the distribution of organic carbon (OC) between particle size fractions in near-surface (0-0.05 m) soil and the water erosion-induced redistribution of particle-associated OC over a grass-shrub ecotone, in a semiarid landscape, subject to land degradation. Coarse ( > 2 mm) particles have comparable average OC concentrations to the fine ( < 2 mm) particles, accounting for ~24-38% of the OC stock in the near-surface soil. This may be due to aggregate stabilization by precipitated calcium carbonate in these calcareous arid soils. Critically, standard protocols assuming that coarse fraction particles contain no OC are likely to underestimate soil OC stocks substantially, especially in soils with strongly stabilized aggregates. Sediment eroded from four hillslope scale (10 × 30 m) sites during rainstorm events was monitored over four annual monsoon seasons. Eroded sediment was significantly enriched in OC; enrichment increased significantly across the grass-shrub ecotone and appears to be an enduring phenomenon probably sustained through the dynamic replacement of preferentially removed organic matter. The average erosion-induced OC event yield increased sixfold across th e ecotone from grass-dominated to shrub-dominated ecosystems, due to both greater erosion and greater OC enrichment. This erosional pathway is rarely considered when comparing the carbon budgets of grasslands and shrublands, yet this accelerated efflux of OC may be important for long-term carbon storage potentials of dryland ecosystems.
Abstract.
Puttock A, Graham HA, Cunliffe AM, Elliott M, Brazier RE (2016). Eurasian beaver activity increases water storage, attenuates flow and mitigates diffuse pollution from intensively-managed grasslands.
Science of the Total Environment,
576, 430-443.
Abstract:
Eurasian beaver activity increases water storage, attenuates flow and mitigates diffuse pollution from intensively-managed grasslands
© 2016 the Authors Beavers are the archetypal keystone species, which can profoundly alter ecosystem structure and function through their ecosystem engineering activity, most notably the building of dams. This can have a major impact upon water resource management, flow regimes and water quality. Previous research has predominantly focused on the activities of North American beaver (Castor canadensis) located in very different environments, to the intensive lowland agricultural landscapes of the United Kingdom and elsewhere in Europe. Two Eurasian beavers (Castor fiber) were introduced to a wooded site, situated on a first order tributary, draining from intensively managed grassland. The site was monitored to understand impacts upon water storage, flow regimes and water quality. Results indicated that beaver activity, primarily via the creation of 13 dams, has increased water storage within the site (holding ca. 1000 m 3 in beaver ponds) and beavers were likely to have had a significant flow attenuation impact, as determined from peak discharges (mean 30 ± 19% reduction), total discharges (mean 34 ± 9% reduction) and peak rainfall to peak discharge lag times (mean 29 ± 21% increase) during storm events. Event monitoring of water entering and leaving the site showed lower concentrations of suspended sediment, nitrogen and phosphate leaving the site (e.g. for suspended sediment; average entering site: 112 ± 72 mg l − 1 , average leaving site: 39 ± 37 mg l − 1 ). Combined with attenuated flows, this resulted in lower diffuse pollutant loads in water downstream. Conversely, dissolved organic carbon concentrations and loads downstream were higher. These observed changes are argued to be directly attributable to beaver activity at the site which has created a diverse wetland environment, reducing downstream hydrological connectivity. Results have important implications for beaver reintroduction programs which may provide nature based solutions to the catchment-scale water resource management issues that are faced in agricultural landscapes.
Abstract.
Luscombe DJ, Anderson K, Grand-Clement E, Gatis N, Ashe J, Benaud P, Smith D, Brazier RE (2016). How does drainage alter the hydrology of shallow degraded peatlands across multiple spatial scales?.
Journal of Hydrology,
541, 1329-1339.
Abstract:
How does drainage alter the hydrology of shallow degraded peatlands across multiple spatial scales?
Shallow, degraded peatlands differ in both their structure and function from deeper, peatland ecosystems. Previous work has shown that shallow, drained peatlands demonstrate rapid storm runoff that is only minimally controlled by antecedent hydrological conditions. However, such peatlands are also known to exhibit significant variation in ecohydrological organisation and structure across different spatial scales. In addition, predictions of hydrological response using spatially distributed numerical models of rainfall-runoff may be flawed unless they are evaluated with datasets describing the spatial variability of hydrological responses. This paper evaluates to what extent, flow generation and water storage within shallow, degraded peatland catchments may be controlled by the spatial attributes of the contributing area of the peatland, the drainage ditch size, morphology and geometry. Results from an experiment conducted over multiple spatial scales and multi-annual timescales highlights that subtle variations in the local slope and topography account for the long-term spatial patterns of water table depth. Neither the local scale of the drainage feature or the topographic contributing area is shown to be a definitive predictor of runoff in the studied catchments. Results also highlight the importance of using spatially distributed observations to ensure that estimates of water storage and runoff are representative of the fine scale spatial variability that occurs in such damaged and shallow peatlands.
Abstract.
Ritson JP, Bell M, Brazier RE, Grand-Clement E, Graham NJD, Freeman C, Smith D, Templeton MR, Clark JM (2016). Managing peatland vegetation for drinking water treatment.
Sci Rep,
6Abstract:
Managing peatland vegetation for drinking water treatment.
Peatland ecosystem services include drinking water provision, flood mitigation, habitat provision and carbon sequestration. Dissolved organic carbon (DOC) removal is a key treatment process for the supply of potable water downstream from peat-dominated catchments. A transition from peat-forming Sphagnum moss to vascular plants has been observed in peatlands degraded by (a) land management, (b) atmospheric deposition and (c) climate change. Here within we show that the presence of vascular plants with higher annual above-ground biomass production leads to a seasonal addition of labile plant material into the peatland ecosystem as litter recalcitrance is lower. The net effect will be a smaller litter carbon pool due to higher rates of decomposition, and a greater seasonal pattern of DOC flux. Conventional water treatment involving coagulation-flocculation-sedimentation may be impeded by vascular plant-derived DOC. It has been shown that vascular plant-derived DOC is more difficult to remove via these methods than DOC derived from Sphagnum, whilst also being less susceptible to microbial mineralisation before reaching the treatment works. These results provide evidence that practices aimed at re-establishing Sphagnum moss on degraded peatlands could reduce costs and improve efficacy at water treatment works, offering an alternative to 'end-of-pipe' solutions through management of ecosystem service provision.
Abstract.
Author URL.
Peukert S, Griffith BA, Murray PJ, Macleod CJA, Brazier RE (2016). Spatial variation in soil properties and diffuse losses between and within grassland fields with similar short-term management.
European Journal of Soil Science,
67(4), 386-396.
Abstract:
Spatial variation in soil properties and diffuse losses between and within grassland fields with similar short-term management
One of the major challenges for agriculture is to understand the effects of agricultural practices on soil properties and diffuse pollution, to support practical farm-scale land management. Three conventionally managed grassland fields with similar short-term management, but different ploughing histories, were studied on a long-term research platform: the North Wyke Farm Platform. The aims were to (i) quantify the between-field and within-field spatial variation in soil properties by geostatistical analysis, (ii) understand the effects of soil condition (in terms of nitrogen, phosphorus and carbon contents) on the quality of discharge water and (iii) establish robust baseline data before the implementation of various grassland management scenarios. Although the fields sampled had experienced the same land use and similar management for at least 6 years, there were differences in their mean soil properties. They showed different patterns of soil spatial variation and different rates of diffuse nutrient losses to water. The oldest permanent pasture field had the largest soil macronutrient concentrations and the greatest diffuse nutrient losses. We show that management histories affect soil properties and diffuse losses. Potential gains in herbage yield or benefits in water quality might be achieved by characterizing every field or by area-specific management within fields (a form of precision agriculture for grasslands). Permanent pasture per se cannot be considered a mitigation measure for diffuse pollution. The between- and within-field soil spatial variation emphasizes the importance of baseline characterization and will enable the reliable identification of any effects of future management change on the Farm Platform. Highlights: Quantification of soil and water quality in grassland fields with contrasting management histories. Considerable spatial variation in soil properties and diffuse losses between and within fields. Contrasting management histories within and between fields strongly affected soil and water quality. Careful pasture management needed: the oldest pasture transferred the most nutrients from soil to water.
Abstract.
Cunliffe A, Brazier RE, Anderson K (2016). Ultra-fine grain landscape-scale quantification of dryland vegetation structure with drone-acquired structure-from-motion photogrammetry.
Remote Sensing of Environment,
183, 129-143.
Abstract:
Ultra-fine grain landscape-scale quantification of dryland vegetation structure with drone-acquired structure-from-motion photogrammetry
Covering 40% of the terrestrial surface, dryland ecosystems characteristically have distinct vegetation structures that are strongly linked to their function. Existing survey approaches cannot provide sufficiently fine-resolution data at landscape-level extents to quantify this structure appropriately. Using a small, unpiloted aerial system (UAS) to acquire aerial photographs and processing theses using structure-from-motion (SfM) photogrammetry, three-dimensional models were produced describing the vegetation structure of semi-arid ecosystems at seven sites across a grass–to shrub transition zone. This approach yielded ultra-fine (< 1 cm2) spatial resolution canopy height models over landscape-levels (10 ha), which resolved individual grass tussocks just a few cm3 in volume. Canopy height cumulative distributions for each site illustrated ecologically-significant differences in ecosystem structure. Strong coefficients of determination (r2 from 0.64 to 0.95) supported prediction of above-ground biomass from canopy volume. Canopy volumes, above-ground biomass and carbon stocks were shown to be sensitive to spatial changes in the structure of vegetation communities. The grain of data produced and sensitivity of this approach is invaluable to capture even subtle differences in the structure (and therefore function) of these heterogeneous ecosystems subject to rapid environmental change. The results demonstrate how products from inexpensive UAS coupled with SfM photogrammetry can produce ultra-fine grain biophysical data products, which have the potential to revolutionise scientific understanding of ecology in ecosystems with either spatially or temporally discontinuous canopy cover.
Abstract.
Puttock A, Cunliffe AM, Anderson K, Brazier RE (2015). Aerial photography collected with a multirotor drone reveals impact of Eurasian beaver reintroduction on ecosystem structure.
Journal of Unmanned Vehicle Systems Author URL.
Turley MD, Bilotta GS, Krueger T, Brazier RE, Extence CA (2015). Developing an improved biomonitoring tool for fine sediment: Combining expert knowledge and empirical data.
Ecological Indicators,
54, 82-86.
Abstract:
Developing an improved biomonitoring tool for fine sediment: Combining expert knowledge and empirical data
The Proportion of Sediment-sensitive Invertebrates (PSI) index is a biomonitoring tool that is designed to identify the degree of sedimentation in rivers and streams. Despite having a sound biological basis, the tool has been shown to have only a moderate correlation with fine sediment, which although comparable to other pressure specific indices, limits confidence in its application. The aim of this study was to investigate if the performance of the PSI index could be enhanced through the use of empirical data to supplement the expert knowledge and literature which were used to determine the original four fine sediment sensitivity ratings. The empirical data used, comprised observations of invertebrate abundance and percentage fine sediment, collected across a wide range of reference condition temperate stream and river ecosystems (model training dataset n = 2252). Species were assigned sensitivity weights within a range based on their previously determined sensitivity rating. Using a range of weights acknowledges the breadth of ecological niches that invertebrates occupy and also their differing potential as indicators. The optimum species-specific sensitivity weights were identified using non-linear optimisation, as those that resulted in the highest Spearman's rank correlation coefficient between the Empirically-weighted PSI (E-PSI) scores and deposited fine sediment in the model training dataset. The correlation between percentage fine sediment and E-PSI scores in the test dataset (n = 252) was eight percentage points higher than the correlation between percentage fine sediment and the original PSI scores (E-PSI rs = -0.74, p < 0.01 compared to PSI rs = -0.66, p < 0.01). This study demonstrates the value of combining a sound biological basis with evidence from large empirical datasets, to test and enhance the performance of biomonitoring tools to increase confidence in their application.
Abstract.
Luscombe DJ, Anderson K, Gatis N, Grand-Clement E, Brazier RE (2015). Using airborne thermal imaging data to measure near-surface hydrology in upland ecosystems.
Hydrological Processes,
29(6), 1656-1668.
Abstract:
Using airborne thermal imaging data to measure near-surface hydrology in upland ecosystems
Upland ecosystems are recognized for their importance in providing valuable ecosystem services including water storage, water supply and flood attenuation alongside carbon storage and biodiversity. The UK contains 10-15% of the global resource of upland blanket peatlands, the hydrology and ecology of which are highly sensitive to external anthropogenic and climatic forcing. In particular, drainage of these landscapes for agricultural intensification and peat extraction has resulted in often unquantified damage to the peatland hydrology, and little is understood about the spatially distributed impacts of these practices on near-surface wetness. This paper develops new techniques to extract spatial data describing the near-surface wetness and hydrological behaviour of drained blanket peatlands using airborne thermal imaging data and airborne Light Detection and Ranging (LiDAR) data. The relative thermal emissivity (E{open}r) of the ground surface is mapped and used as a proxy for near-surface wetness. The results show how moorland drainage and land surface structure have an impact on airborne measurements of thermal emissivity. Specifically, we show that information on land surface structure derived from LiDAR can help normalize signals in thermal emissivity data to improve description of hydrological condition across a test catchment in Exmoor, UK. An in situ field hydrological survey was used to validate these findings. We discuss how such data could be used to describe the spatially distributed nature of near-surface water resources, to optimize catchment management schemes and to deliver improved understanding of the drivers of hydrological change in analogous ecosystems.
Abstract.
DeBell L, Anderson K, Brazier RE, Jones L, King N (2015). Water resource management at catchment scales using lightweight UAVs: current capabilities and future perspectives.
Journal of Unmanned Vehicle SystemsAbstract:
Water resource management at catchment scales using lightweight UAVs: current capabilities and future perspectives
Lightweight, portable unmanned aerial vehicles (UAVs) or ‘drones’ are set to become a key component of a water resource management (WRM) toolkit, but are currently not widely used in this context. In practical WRM there is a growing need for fine-scale responsive data, which cannot be delivered from satellites or aircraft in a cost-effective way. Such a capability is needed where water supplies are located in spatially heterogeneous dynamic catchments. In this review, we demonstrate the step change in hydrological process understanding that could be delivered if WRM employed UAVs. The paper discusses a range of pragmatic concepts in UAV science for cost-effective and practical WRM, from choosing the right sensor and platform combination through to practical deployment and data processing challenges. The paper highlights that multi-sensor approaches, such as combining thermal imaging with fine-scale structure-from-motion topographic models are currently best placed to assist WRM decisions because they provide a means of monitoring the spatio-temporal distribution of sources, sinks and flows of water through landscapes. The manuscript highlights areas where research is needed to support the integration of UAVs into practical WRM – e.g. in improving positional accuracy through integration of differential global positioning system sensors, and developing intelligent control of UAV platforms to optimize the accuracy of spatial data capture.
Abstract.
Glendell M, Brazier RE (2014). Accelerated export of sediment and carbon from a landscape under intensive agriculture.
Sci Total Environ,
476-477, 643-656.
Abstract:
Accelerated export of sediment and carbon from a landscape under intensive agriculture.
The export of total organic carbon (particulate and dissolved) from terrestrial to aquatic ecosystems has important implications for water quality and the global carbon cycle. However, most research to date has focused on DOC losses from either forested or peaty catchments, with only limited studies examining the controls and rates of total fluvial carbon losses from agricultural catchments, particularly during storm events. This study examined the controls and fluxes of total suspended sediment (SS), total particulate (TPC) and dissolved organic carbon (DOC) from two adjacent catchments with contrasting intensive agricultural and semi-natural land-use. Data from 35 individual storm events showed that the agricultural catchment exported significantly higher SS concentrations on a storm-by-storm basis than the semi-natural catchment, with peak discharge exerting a greater control over SS, TPC and DOC concentrations. Baseflow DOC concentrations in the agricultural catchment were significantly higher. DOC quality monitored during one simultaneous rainfall event differed between the two study catchments, with more humic, higher molecular weight compounds prevailing in the agricultural catchment and lower molecular weight compounds prevailing in the semi-natural catchment. During an eight month period for which a comparable continuous turbidity record was available, the estimated SS yields from the agricultural catchment were higher than from the semi-natural catchment. Further, the agricultural catchment exported proportionally more TPC and a comparable amount of DOC, despite a lower total soil carbon pool. These results suggest that altered hydrological and biogeochemical processes within the agricultural catchment, including accelerated soil erosion and soil organic matter turnover, contributed to an enhanced fluvial SS and carbon export. Thus, we argue that enhancing semi-natural vegetation within intensively farmed catchments could reduce sediment and carbon losses from these areas and increase their resilience to more extreme hydrological events, anticipated as a result of climate change.
Abstract.
Author URL.
Brazier RE, Turnbull L, Wainwright J, Bol R (2014). Carbon loss by water erosion in drylands: Implications from a study of vegetation change in the south-west USA.
Hydrological Processes,
28(4), 2212-2222.
Abstract:
Carbon loss by water erosion in drylands: Implications from a study of vegetation change in the south-west USA
Soil organic carbon (SOC) is an important component of the global carbon cycle yet is rarely quantified adequately in terms of its spatial variability resulting from losses of SOC due to erosion by water. Furthermore, in drylands, little is known about the effect of widespread vegetation change on changes in SOC stores and the potential for water erosion to redistribute SOC around the landscape especially during high-magnitude run-off events (flash floods). This study assesses the change in SOC stores across a shrub-encroachment gradient in the Chihuahuan Desert of the south-west USA. A robust estimate of SOC storage in surface soils is presented, indicating that more SOC is stored beneath vegetation than in bare soil areas. In addition, the change in SOC storage over a shrub-encroachment gradient is shown to be nonlinear and highly variable within each vegetation type. Over the gradient of vegetation change, the heterogeneity of SOC increases, and newer carbon from C3 plants becomes dominant. This increase in the heterogeneity of SOC is related to an increase in water erosion and SOC loss from inter-shrub areas, which is self-reinforcing. Shrub-dominated drylands lose more than three times as much SOC as their grass counterparts. The implications of this study are twofold: (1) quantifying the effects of vegetation change on carbon loss via water erosion and the highly variable effects of land degradation on soil carbon stocks is critical. (2) If landscape-scale understanding of carbon loss by water erosion in drylands is required, studies must characterize the heterogeneity of ecosystem structure and its effects on ecosystem function across ecotones subject to vegetation change. © 2013 John Wiley & Sons, Ltd.
Abstract.
Turley MD, Bilotta GS, Extence CA, Brazier RE (2014). Evaluation of a fine sediment biomonitoring tool across a wide range of temperate rivers and streams.
Freshwater Biology,
59(11), 2268-2277.
Abstract:
Evaluation of a fine sediment biomonitoring tool across a wide range of temperate rivers and streams
Elevated levels of fine sediment (suspended and deposited) are a common cause of ecological degradation in freshwater ecosystems. However, it is time-consuming and expensive to monitor these parameters to support national and international water resource legislation. The Proportion of Sediment-sensitive Invertebrates (PSI) index is a biomonitoring tool that is designed to identify the degree of sedimentation in rivers and streams. Despite having a sound biological basis, until now, the PSI index has only been tested against observed fine sediment data in two catchments; other published applications of the PSI index have relied on inferred fine sediment values. In this study, we report the results of a comprehensive analysis of the performance of the PSI index across a wide range of reference condition temperate stream and river ecosystems, including 835 sites with data on deposited sediment and 451 sites with data on suspended solids (>12 500 data points measured between 1978 and 2002). The effect of taxonomic level and taxonomic resolution on the performance of the PSI index was also examined, as was the performance of the PSI index against other non-sediment-specific indices, including Average Score Per Taxon (ASPT), Lotic-invertebrate Index for Flow Evaluation (LIFE), Ephemeroptera, Plecoptera and Trichoptera (EPT) abundance, % EPT abundance, EPT richness and % EPT richness. The results of this study show that the PSI index was more correlated with fine sediment metrics than the other biological indices tested: rs = -0.64, (P < 0.01, n = 2502) for deposited sediment and rs = -0.50 (P < 0.01, n = 1353) for suspended solids. We highlight the optimal conditions for applying the PSI index, in its current form. Given the variability in the relationship between PSI and fine sediment metrics, we propose that the use of data from more objective, quantitative methods of measuring deposited fine sediment may help to enhance the performance of the model for future applications and advance understanding of fine sediment dynamics and the pressure-response relationship.
Abstract.
Liu S, Brazier RE, Heathwaite AL, Liu W (2014). Fully integrated approach: an alternative solution of coupling a GIS and diffuse pollution models.
FRONTIERS OF ENVIRONMENTAL SCIENCE & ENGINEERING,
8(4), 616-623.
Author URL.
Peukert S, Griffith BA, Murray PJ, Macleod CJA, Brazier RE (2014). Intensive management in grasslands causes diffuse water pollution at the farm scale.
Journal of Environmental Quality,
43(6), 2009-2023.
Abstract:
Intensive management in grasslands causes diffuse water pollution at the farm scale
Arable land use is generally assumed to be the largest contributor to agricultural diffuse pollution. This study adds to the growing evidence that conventional temperate intensively managed lowland grasslands contribute significantly to soil erosion and diffuse pollution rates. This is the first grassland study to monitor hydrological characteristics and multiple pollutant fluxes (suspended sediment [SS] and the macronutrients: total oxidized nitrogen-N [TONN], total phosphorus [TP], and total carbon [TC]) at high temporal resolution (monitoring up to every 15 min) over 1 yr. Monitoring was conducted across three fields (6.5-7.5 ha) on the North Wyke Farm Platform, UK. The estimated annual erosion rates (up to 527.4 kg ha-1), TP losses (up to 0.9 kg ha-1), and TC losses (up to 179 kg ha-1) were similar to or exceeded the losses reported for other grassland, mixed land-use, and arable sites. Annual yields of TONN (up to 3 kg ha-1) were less than arable land-use fluxes and earlier grassland N studies, an important result as the study site is situated within a Nitrate Vulnerable Zone. The high-resolution monitoring allowed detailed "system's functioning" understanding of hydrological processes, mobilization- transport pathways of individual pollutants, and the changes of the relative importance of diffuse pollutants through flow conditions and time. Suspended sediment and TP concentrations frequently exceeded water quality guidelines recommended by the European Freshwater Fisheries Directive (25 mg L-1) and the European Water Framework Directive (0.04 mg soluble reactive P L-1), suggesting that intensively managed grasslands pose a significant threat to receiving surface waters. Such sediment and nutrient losses from intensively managed grasslands should be acknowledged in land management guidelines and advice for future compliance with surface water quality standards.
Abstract.
Glendell M, Granger SJ, Bol R, Brazier RE (2014). Quantifying the spatial variability of soil physical and chemical properties in relation to mitigation of diffuse water pollution.
Geoderma,
214-215, 25-41.
Abstract:
Quantifying the spatial variability of soil physical and chemical properties in relation to mitigation of diffuse water pollution
Understanding spatial variability of soil properties in response to land-use impacts is essential for evaluating the effectiveness of measures taken to address diffuse water pollution from agriculture. However, despite the growing emphasis on integrated catchment-scale implementation of land-use mitigation measures, the baseline landscape-scale evaluation of the spatial variability of key soil nutrients remains scarce. This study employs a high resolution geostatistical approach to characterise the spatial variability of parameters, including soil bulk density (BD), total soil carbon (TC), nitrogen (TN), phosphorus (TP), inorganic phosphorus (IP), organic phosphorus (OP), stable nitrogen isotope ratio (δ15N), C:N ratio, carbon storage and nitrogen storage in two study catchments with contrasting land uses (agricultural and semi-natural) that are subject to targeted management interventions to reduce flood risk and improve water quality. We found a stronger degree of spatial dependence of all soil properties in the agricultural than the semi-natural catchment, except for bulk density and δ15N. Furthermore, bulk density, TP, IP, OP, C:N ratio, δ15N and carbon storage showed a longer range or spatial auto-correlation in the agricultural catchment. The central tendency (median and mean) of all soil properties was also significantly different between the two catchments, with the exception of IP and δ15N. The spatial correlations between the soil properties pointed to the mechanisms that were responsible for the observed differences, whilst the krigged surfaces of soil variables identified most likely critical source areas for targeted land management interventions to improve water quality. Arable and intensive grasslands were identified as 'high-impact' land uses, associated with negative alteration of soil properties and increased diffuse water pollution, whilst moorland was a 'low impact' land use associated with improved water quality. A comparison with the national soil survey dataset shows that whilst it can be relied upon for the broad characterisation of carbon and TP stocks in the two study catchments, it underestimates the spatial variability of key soil properties in certain soil types and land uses. As the restoration of soil spatial heterogeneity may take several decades, a high resolution geostatistical approach should be included in the future design of catchment-scale monitoring schemes to inform catchment management strategies and elucidate the time frame over which landscape scale improvements in soil properties and corresponding ecosystem services can be achieved. © 2013 Elsevier B.V.
Abstract.
Ritson JP, Bell M, Graham NJD, Templeton MR, Brazier RE, Verhoef A, Freeman C, Clark JM (2014). Simulated climate change impact on summer dissolved organic carbon release from peat and surface vegetation: implications for drinking water treatment.
Water Res,
67, 66-76.
Abstract:
Simulated climate change impact on summer dissolved organic carbon release from peat and surface vegetation: implications for drinking water treatment.
Uncertainty regarding changes in dissolved organic carbon (DOC) quantity and quality has created interest in managing peatlands for their ecosystem services such as drinking water provision. The evidence base for such interventions is, however, sometimes contradictory. We performed a laboratory climate manipulation using a factorial design on two dominant peatland vegetation types (Calluna vulgaris and Sphagnum Spp.) and a peat soil collected from a drinking water catchment in Exmoor National Park, UK. Temperature and rainfall were set to represent baseline and future conditions under the UKCP09 2080s high emissions scenario for July and August. DOC leachate then underwent standard water treatment of coagulation/flocculation before chlorination. C. vulgaris leached more DOC than Sphagnum Spp. (7.17 versus 3.00 mg g(-1)) with higher specific ultraviolet (SUVA) values and a greater sensitivity to climate, leaching more DOC under simulated future conditions. The peat soil leached less DOC (0.37 mg g(-1)) than the vegetation and was less sensitive to climate. Differences in coagulation removal efficiency between the DOC sources appears to be driven by relative solubilisation of protein-like DOC, observed through the fluorescence peak C/T. Post-coagulation only differences between vegetation types were detected for the regulated disinfection by-products (DBPs), suggesting climate change influence at this scale can be removed via coagulation. Our results suggest current biodiversity restoration programmes to encourage Sphagnum Spp. will result in lower DOC concentrations and SUVA values, particularly with warmer and drier summers.
Abstract.
Author URL.
Hutton C, Nicholas A, Brazier R (2014). Sub-grid scale parameterization of hillslope runoff and erosion processes for catchment-scale models of semi-arid landscapes.
Hydrological Processes,
28(4), 1713-1721.
Abstract:
Sub-grid scale parameterization of hillslope runoff and erosion processes for catchment-scale models of semi-arid landscapes
The processes of hillslope runoff and erosion are typically represented at coarse spatial resolution in catchment-scale models due to computational limitations. Such representation typically fails to incorporate the important effects of topographic heterogeneity on runoff generation, overland flow, and soil erosion. These limitations currently undermine the application of distributed catchment models to understand the importance of thresholds and connectivity on hillslope and catchment-scale runoff and erosion, particularly in semi-arid environments. This paper presents a method for incorporating high-resolution topographic data to improve sub-grid scale parameterization of hillslope overland flow and erosion models. Results derived from simulations conducted using a kinematic wave overland flow model at 0.5m spatial resolution are used to parameterize the depth-discharge relationship in the overland flow model when applied at 16m resolution. The high-resolution simulations are also used to derive a more realistic parameterization of excess flow shear stress for use in the 16m resolution erosion model. Incorporating the sub-grid scale parameterization in the coarse-resolution model (16m) leads to improved predictions of overland flow and erosion when evaluated using results derived from high-resolution (0.5m) model simulations. The improvement in performance is observed for a range of event magnitudes and is most notable for erosion estimates due to the non-linear dependency between the rates of erosion and overland flow. © 2013 John Wiley & Sons, Ltd.
Abstract.
Glendell M, Extence C, Chadd R, Brazier RE (2014). Testing the pressure-specific invertebrate index (PSI) as a tool for determining ecologically relevant targets for reducing sedimentation in streams.
Freshwater Biology,
59(2), 353-367.
Abstract:
Testing the pressure-specific invertebrate index (PSI) as a tool for determining ecologically relevant targets for reducing sedimentation in streams
Sedimentation is a major cause of river impairment and water pollution worldwide. However, setting an ecologically meaningful sedimentation target is proving challenging due to significant gaps in the understanding of quantitative links between sedimentation and ecological response as well as variability between different types of surface waters. This study evaluates the utility of a new pressure-specific macroinvertebrate index, Proportion of Sediment-sensitive Invertebrates (PSI), to act as a simple tool for measuring sedimentation impacts and setting ecologically relevant sedimentation targets. Five macroinvertebrate indices were calculated from 51 samples taken from 13 sampling locations across two neighbouring, but contrasting study catchments in spring and autumn 2010 and 2011. For four of these, environmental quality indices (EQIs) were also calculated as a proportion of observed to expected (O:E) macroinvertebrate scores, which were predicted for a theoretical pristine invertebrate community using the River Invertebrate Prediction and Classification System model. Principal component analysis has shown a clear hydromorphological and sedimentation gradient within the two study catchments. A generalised hierarchical mixed model with site as a random factor and % fine bed sediment as a fixed factor found a significant relationship between PSI and O:E PSI and % fine bed sediment cover at reach-scale sampling resolution over a moderate gradient of impact. Lotic Index for Flow Evaluation (LIFE) scores and Ephemeroptera-Plecoptera-Trichoptera (EPT) % abundance were also related to % fine bed sediment cover. However, PSI was more strongly related to % fine bed sediment cover than either LIFE or EPT % abundance. While PSI and O:E PSI were correlated with LIFE and O:E LIFE, PSI was not correlated with EPT % abundance, which suggests a differentiated response of these metrics to multiple stressors. The relationship between PSI and other invertebrate metrics should be subjected to further testing along a pronounced gradient of multiple stressors, as our findings suggest that PSI and % fine bed sediment cover have the potential to provide simple, sensitive and effective tools for setting of 'twin' ecological and physical sedimentation targets and add additional exploratory power to the existing suite of macroinvertebrate indices. © 2013 John Wiley & Sons Ltd.
Abstract.
Luscombe DJ, Anderson K, Gatis N, Wetherelt A, Grand-Clement E, Brazier RE (2014). What does airborne LiDAR really measure in upland ecosystems?.
EcohydrologyAbstract:
What does airborne LiDAR really measure in upland ecosystems?
Airborne laser scanning systems (Light Detection and Ranging, LiDAR) are very well suited to the study of landscape and vegetation structure over large extents. Spatially distributed measurements describing the three-dimensional character of landscape surfaces and vegetation architecture can be used to understand eco-geomorphic and ecohydrological processes, and this is particularly pertinent in peatlands given the increasing recognition that these landscapes provide a variety of ecosystem services (water provision, flood mitigation and carbon sequestration). In using LiDAR data for monitoring peatlands, it is important to understand how well peatland surface structures (with fine length scales) can be described. Our approach integrates two laser scanning technologies, namely terrestrial laser scanning (TLS) and airborne LiDAR surveys, to assess how effective airborne LiDAR is at measuring these fine-scale microtopographic ecohydrological structures. By combining airborne and TLS, we demonstrate an improved spatial understanding of the signal measured by the airborne LiDAR. Critically, results demonstrate that LiDAR digital surface models are subject to specific errors related to short-sward ecosystem structure, causing the vegetation canopy height and surface-drainage network depth to be underestimated. TLS is shown to be effective at describing these structures over small extents, allowing the information content and accuracy of airborne LiDAR to be understood and quantified more appropriately. These findings have important implications for the appropriate degree of confidence ecohydrologists can apply to such data when using them as a surrogate for field measurements. They also illustrate the need to couple LiDAR data with ground validation data in order to improve assessment of ecohydrological function in such landscapes. © 2014 John Wiley & Sons, Ltd.
Abstract.
Bol R, Puttock A, Dungait JAJ, Macleod CJA, Brazier RE (2014). Woody plant encroachment into grasslands leads to accelerated erosion of previously stable organic carbon from dryland soils.
Journal of Geophysical Research: Biogeosciences,
119(12), 2345-2357.
Abstract:
Woody plant encroachment into grasslands leads to accelerated erosion of previously stable organic carbon from dryland soils
Drylands worldwide are experiencing rapid and extensive environmental change, concomitant with the encroachment of woody vegetation into grasslands. Woody encroachment leads to changes in both the structure and function of dryland ecosystems and has been shown to result in accelerated soil erosion and loss of soil nutrients. Covering 40% of the terrestrial land surface, dryland environments are of global importance, both as a habitat and a soil carbon store. Relationships between environmental change, soil erosion, and the carbon cycle are uncertain. There is a clear need to further our understanding of dryland vegetation change and impacts on carbon dynamics. Here two grass-to-woody ecotones that occur across large areas of the southwestern United States are investigated. This study takes a multidisciplinary approach, combining ecohydrological monitoring of structure and function and a dual-proxy biogeochemical tracing approach using the unique natural biochemical signatures of the vegetation. Results show that following woody encroachment, not only do these drylands lose significantly more soil and organic carbon via erosion but that this includes significant amounts of legacy organic carbon which would previously have been stable under grass cover. Results suggest that these dryland soils may not act as a stable organic carbon pool, following encroachment and that accelerated erosion of carbon, driven by vegetation change, has important implications for carbon dynamics.
Abstract.
Brazier RE, Turnbull L, Wainwright J, Bol R (2013). Carbon loss by water erosion in drylands: Implications from a study of vegetation change in the south-west USA. Hydrological Processes
Puttock A, Macleod CJA, Bol R, Sessford P, Dungait J, Brazier RE (2013). Changes in ecosystem structure, function and hydrological connectivity control water, soil and carbon losses in semi-arid grass to woody vegetation transitions.
Earth Surface Processes and Landforms,
38(13), 1602-1611.
Abstract:
Changes in ecosystem structure, function and hydrological connectivity control water, soil and carbon losses in semi-arid grass to woody vegetation transitions
Connectivity has recently emerged as a key concept for understanding hydrological response to vegetation change in semi-arid environments, providing an explanatory link between abiotic and biotic, structure and function. Reduced vegetation cover following woody encroachment, generally promotes longer, more connected overland flow pathways, which has the potential to result in an accentuated rainfall-runoff response and fluxes of both soil erosion and carbon. This paper investigates changing hydrological connectivity as an emergent property of changing ecosystem structure over two contrasting semi-arid grass to woody vegetation transitions in New Mexico, USA. Vegetation structure is quantified to evaluate if it can be used to explain observed variations in water, sediment and carbon fluxes. Hydrological connectivity is quantified using a flow length metric, combining topographic and vegetation cover data. Results demonstrate that the two woody-dominated sites have significantly longer mean flowpath lengths (4·3m), than the grass-dominated sites (2·4m). Mean flowpath lengths illustrate a significant positive relationship with the functional response. The woody-dominated sites lost more water, soil and carbon than their grassland counterparts. Woody sites erode more, with mean event-based sediment yields of 1203g, compared to 295g from grasslands. In addition, the woody sites lost more organic carbon, with mean event yields of 39g compared to 5g from grassland sites. Finally, hydrological connectivity (expressed as mean flowpath length) is discussed as a meaningful measure of the interaction between structure and function and how this manifests under the extreme rainfall that occurs in semi-arid deserts. In combination with rainfall characteristics, connectivity emerges as a useful tool to explain the impact of vegetation change on water, soil and carbon losses across semi-arid environments.Copyright © 2013 John Wiley & Sons, Ltd.
Abstract.
Brazier RE (2013). Erosion and Sediment Transport: Finding Simplicity in a Complicated Erosion Model.
, 253-266.
Abstract:
Erosion and Sediment Transport: Finding Simplicity in a Complicated Erosion Model
Problems of erosion and sediment transport are concerned with the same question of how does water interact with sediment to control landscape morphology. This chapter demonstrates how a simplified, or minimum information requirement (MIR) version of water erosion prediction project (WEPP) - MIRSED - can be applied to predict patterns of erosion over a large spatial extent. The results of using this model are evaluated in terms of available observed data. The data are also shown to be highly variable, in space, reflecting the complexity of hillslope-scale erosion processes and the interactions between land use, soil type and topography that controls hillslope erosion. In this chapter, results are generated based upon dominant soil type, distribution of land use and the use of both average slopes and slope distributions from each grid cell across a catchment or region. © 2013 John Wiley & Sons, Ltd.
Abstract.
Peukert S, Bol R, Roberts W, MacLeod CJA, Murray PJ, Dixon ER, Brazier RE (2013). Erratum: Understanding spatial variability of soil properties: a key step in establishing field to farmscale agroecosystem experiments (Rapid Communications in Mass Spectrometry (2012) 26 (2413-2421) DOI: 10.1002/rcm.6336). Rapid Communications in Mass Spectrometry, 27(1).
Scholefield P, Heathwaite AL, Brazier RE, Page T, Schärer M, Beven K, Hodgkinson R, Withers P, Walling D, Haygarth PM, et al (2013). Estimating phosphorus delivery from land to water in headwater catchments using a fuzzy decision tree approach.
Soil Use and Management,
29(SUPPL.1), 175-186.
Abstract:
Estimating phosphorus delivery from land to water in headwater catchments using a fuzzy decision tree approach
The pathway that delivers mobilized phosphorus (P) from source to surface water is conceptually complex. Firstly, P mobilization itself, either through mechanical disturbance of the soil or through chemical dissolution or weathering, is difficult to measure in situ; secondly, the annual flow-weighted mean concentration of P is a difficult metric to gather. Summarizing these pathway processes as the ratio of the delivered P to the mobilized fraction of P assists in the quantification and assessment of the P transfer continuum. The proportion of this mobilized P that is subsequently delivered to the watercourse is also difficult to quantify. A range of P models already exist that aim to predict P mobilization and delivery. Reasonable estimates can be made for the outputs of P from a plot or small catchment over a series of events. Current models mainly rely on empirical data or expert judgment to derive appropriate coefficients of P transfer and delivery. This paper describes the research designed to evaluate the range of delivery coefficients from headwater catchments that might be anticipated for different land-use regions across the UK. These coefficients were evaluated within a fuzzy decision tree framework. The delivery coefficients used in this study covered a broad range of possible values from all available data describing P fluxes from headwater catchments in the UK. The results of this work indicate that delivery coefficients are a useful way of summarizing the mobilization behaviour of a headwater catchment. Mean delivery coefficients above unity were present in four of 18 catchments, indicating higher than average delivery, probably due to intensive agricultural management practices. This first use of a fuzzy or uncertain approach to model P delivery in the UK has generated potentially promising results, and a methodology has been developed for producing delivery coefficients using sparse data, which may be applicable to other headwater catchments. © 2013 the Authors. Soil Use and Management © 2013 British Society of Soil Science.
Abstract.
Grand-Clement E, Anderson K, Smith D, Luscombe D, Gatis N, Ross M, Brazier RE (2013). Evaluating ecosystem goods and services after restoration of marginal upland peatlands in South-West England.
J Appl Ecol,
50(2), 324-334.
Author URL.
Croft H, Anderson K, Brazier RE, Kuhn NJ (2013). Modeling fine-scale soil surface structure using geostatistics.
Water Resources Research,
49(4), 1858-1870.
Abstract:
Modeling fine-scale soil surface structure using geostatistics
There is widespread recognition that spatially distributed information on soil surface roughness (SSR) is required for hydrological and geomorphological applications. Such information is necessary to describe variability in soil structure, which is highly heterogeneous in time and space, to parameterize hydrology and erosion models and to understand the temporal evolution of the soil surface in response to rainfall. This paper demonstrates how results from semivariogram analysis can quantify key elements of SSR for such applications. Three soil types (silt, silt loam, and silty clay) were used to show how different types of structural variance in SSR evolve during simulated rainfall events. All three soil types were progressively degraded using artificial rainfall to produce a series of roughness states. A calibrated laser profiling instrument was used to measure SSR over a 10 cm × 10 cm spatial extent, at a 2 mm resolution. These data were geostatistically analyzed in the context of aggregate breakdown and soil crusting. The results show that such processes are represented by a quantifiable decrease in sill variance, from 7.81 (control) to 0.94 (after 60 min of rainfall). Soil surface features such as soil cracks, tillage lines and erosional areas were quantified by local maxima in semivariance at a given length scale. This research demonstrates that semivariogram analysis can retrieve spatiotemporal variations in soil surface condition; in order to provide information on hydrological pathways. Consequently, geostatistically derived SSR shows strong potential for inclusion as spatial information in hydrology and erosion models to represent complex surface processes at different soil structural scales. © 2013. American Geophysical Union. All Rights Reserved.
Abstract.
Hutton C, Nicholas A, Brazier R (2013). Sub-grid scale parameterization of hillslope runoff and erosion processes for catchment-scale models of semi-arid landscapes. Hydrological Processes
Peukert S, Bol R, Roberts W, Macleod CJA, Murray PJ, Dixon ER, Brazier RE (2013). Understanding spatial variability of soil properties: a key step in establishing field- to farm-scale agro-ecosystem experiments (vol 26, pg 2413, 2012).
RAPID COMMUNICATIONS IN MASS SPECTROMETRY,
27(1), 284-284.
Author URL.
Old GH, Naden PS, Granger SJ, Bilotta GS, Brazier RE, Macleod CJA, Krueger T, Bol R, Hawkins JMB, Haygarth P, et al (2012). A novel application of natural fluorescence to understand the sources and transport pathways of pollutants from livestock farming in small headwater catchments.
Science of the Total Environment,
417-418, 169-182.
Abstract:
A novel application of natural fluorescence to understand the sources and transport pathways of pollutants from livestock farming in small headwater catchments
This paper demonstrates the application of a low-cost and rapid natural fluorescence technique for tracing and quantifying the transport of pollutants from livestock farming through a small headwater catchment. Fluorescence intensities of Dissolved Organic Matter (DOM) present in different pollutant sources and drainage waters in the Den Brook catchment (Devon, UK) were monitored through storm events occurring between January 2007 and June 2008. Contrasting fluorescence signals from different sources confirmed the technique's usefulness as a tracer of pollutants from livestock farming. Changes in fluorescence intensities of drainage waters throughout storm events were used to assess the dynamics of key pollutant sources. The farmyard area of the catchment studied was shown to contribute polluted runoff at the onset of storm events in response to only small amounts of rain, when flows in the Den Brook first-order channel were low. The application of slurry to a field within the catchment did not elevate the fluorescence of drainage waters during storm events suggesting that when slurry is applied to undrained fields the fluorescent DOM may become quickly adsorbed onto soil particles and/or immobilised through bacterial breakdown. Fluorescence intensities of drainage waters were successfully combined with discharge data in a two component mixing model to estimate pollutant fluxes from key sources during the January 2007 storm event. The farmyard was shown to be the dominant source of tryptophan-like material, contributing 61-81% of the total event flux at the catchment outlet. High spatial and temporal resolution measurements of fluorescence, possibly using novel in-situ fluorimeters, may thus have great potential in quickly identifying and quantifying the presence, dynamics and sources of pollutants from livestock farming in catchments. © 2011 Elsevier B.V.
Abstract.
Krueger T, Quinton JN, Freer J, MacLeod CJA, Bilotta GS, Brazier RE, Hawkins JMB, Haygarth PM (2012). Comparing empirical models for sediment and phosphorus transfer from soils to water at field and catchment scale under data uncertainty.
European Journal of Soil Science,
63(2), 211-223.
Abstract:
Comparing empirical models for sediment and phosphorus transfer from soils to water at field and catchment scale under data uncertainty
Soils are important sources of sediment and phosphorus in rural catchments, necessitating the development of mathematical models for impact assessment. In this paper, multiple empirical models are tested on an event basis at four nested locations in an intensively managed grassland headwater catchment while accounting for parameter and data uncertainties using extended Generalized Likelihood Uncertainty Estimation (GLUE). The study provides the first template of model comparison under data uncertainty in soil erosion and phosphorus transfer modelling as well as hypotheses of soil and water processes in the study catchment. A fodder field, yielding large sediment and phosphorus concentrations in runoff, is characterized by inter-event variation in sediment-discharge relationship, mild intra-event hysteretic behaviour and seemingly random erosion incidents. Sediment-discharge variation is partly formalized by parameter variation as a function of antecedent soil moisture, indicative of a gradual shift from transport- to source-limited behaviour, decreasing soil erodibility and/or decreasing initial flow erosivity and transport capacity with increasing antecedent wetness. The catchment outlet appears to be source-limited while converging flows with different sediment concentrations, variable erosion processes and/or sporadic entrainment of near- or in-stream sediments gain importance. Phosphorus dynamics are strongly linked to those of sediment. Non-linearities can be explained by preferential transfer of phosphorus-rich organic matter at small flows while there is no significant evidence of preferential transfer of phosphorus-rich mineral fines. Iterating between collecting data, constraining uncertainties and rejecting and improving models is suggested as a consistent framework for understanding soil erosion and phosphorus movement. © 2012 the Authors. Journal compilation © 2012 British Society of Soil Science.
Abstract.
Hutton C, Brazier R (2012). Quantifying riparian zone structure from airborne LiDAR: Vegetation filtering, anisotropic interpolation, and uncertainty propagation.
Journal of Hydrology,
442-443, 36-45.
Abstract:
Quantifying riparian zone structure from airborne LiDAR: Vegetation filtering, anisotropic interpolation, and uncertainty propagation
Advances in remote sensing technology, notably in airborne Light Detection and Ranging (LiDAR), have facilitated the acquisition of high-resolution topographic and vegetation datasets over increasingly large areas. Whilst such datasets may provide quantitative information on surface morphology and vegetation structure in riparian zones, existing approaches for processing raw LiDAR data perform poorly in riparian channel environments. A new algorithm for separating vegetation from topography in raw LiDAR data, and the performance of the Elliptical Inverse Distance Weighting (EIDW) procedure for interpolating the remaining ground points, are evaluated using data derived from a semi-arid ephemeral river. The filtering procedure, which first applies a threshold (either slope or elevation) to classify vegetation high-points, and second a regional growing algorithm from these high-points, avoids the classification of high channel banks as vegetation, preserving existing channel morphology for subsequent interpolation (2.90-9.21% calibration error; 4.53-7.44% error in evaluation for slope threshold). EIDW, which accounts for surface anisotropy by converting the remaining elevation points to streamwise co-ordinates, can outperform isoptropic interpolation (IDW) on channel banks, however, performs less well in isotropic conditions, and when local anisotropy is different to that of the main channel. A key finding of this research is that filtering parameter uncertainty affects the performance of the interpolation procedure; resultant errors may propagate into the Digital Elevation Model (DEM) and subsequently derived products, such as Canopy Height Models (CHMs). Consequently, it is important that this uncertainty is assessed. Understanding and developing methods to deal with such errors is important to inform users of the true quality of laser scanning products, such that they can be used effectively in hydrological applications. © 2012 Elsevier B.V.
Abstract.
Puttock A, Dungait JAJ, Bol R, Dixon ER, Macleod CJA, Brazier RE (2012). Stable carbon isotope analysis of fluvial sediment fluxes over two contrasting C<inf>4</inf>-C<inf>3</inf> semi-arid vegetation transitions.
Rapid Communications in Mass Spectrometry,
26(20), 2386-2392.
Abstract:
Stable carbon isotope analysis of fluvial sediment fluxes over two contrasting C4-C3 semi-arid vegetation transitions
RATIONALE: Globally, many drylands are experiencing the encroachment of woody vegetation into grasslands. These changes in ecosystem structure and processes can result in increased sediment and nutrient fluxes due to fluvial erosion. As these changes are often accompanied by a shift from C4 to C3 vegetation with characteristic δ13C values, stable isotope analysis provides a promising mechanism for tracing these fluxes. METHODS: Input vegetation, surface sediment and fluvially eroded sediment samples were collected across two contrasting C4-C3 dryland vegetation transitions in New Mexico, USA. Isotope ratio mass spectrometric analyses were performed using a Carlo Erba NA2000 analyser interfaced to a SerCon 20-22 isotope ratio mass spectrometer to determine bulk δ13C values. RESULTS: Stable isotope analyses of contemporary input vegetation and surface sediments over the monitored transitions showed significant differences (p
Abstract.
Hoang L, Dessai S, Brazier R (2012). Uncertainty analysis of an integrated water system in southern England: Exploring physical and socio-economic uncertainties.
iEMSs 2012 - Managing Resources of a Limited Planet: Proceedings of the 6th Biennial Meeting of the International Environmental Modelling and Software Society, 981-988.
Abstract:
Uncertainty analysis of an integrated water system in southern England: Exploring physical and socio-economic uncertainties
Climate change risk assessment of water resources is fraught with uncertainty. Such uncertainty is not only the accumulation of individual uncertainty components, but also the results of intricate interactions amongst the physical environment and the socio-economic system. There is often a mismatch of model representation of these two systems: while uncertainty of physical factors has often been described using quantitative methods, socio-economic factors have largely been qualitative. In our drought assessment case study, we evaluate uncertainty in the physical factors and demand responses in the context of climate change. In particular, we focus on structural uncertainty of the supply component and data uncertainty of the demand component. To explore structural uncertainty, a model of fine scale that has nodes representing real supply and demand sources was used as a reference model; another model at the water resource zone scale was used as an emulator to reflect information loss if a coarser spatial resolution is used. The input data are the UK Climate Projections 2009, 1989-2011 historic demand and 1961-1990 historic climate data. The main model output of interest is failure of supply. We found that uncertainty from the hydrological model contributes a high uncertainty margins to the final model results; in this case study it is more influential than uncertainty from either projected climate change or demand growth.
Abstract.
Peukert S, Bol R, Roberts W, Macleod CJA, Murray PJ, Dixon ER, Brazier RE (2012). Understanding spatial variability of soil properties: a key step in establishing field- to farm-scale agro-ecosystem experiments.
Rapid Communications in Mass Spectrometry,
26(20), 2413-2421.
Abstract:
Understanding spatial variability of soil properties: a key step in establishing field- to farm-scale agro-ecosystem experiments
RATIONALE: the spatial variability of soil properties is poorly understood, despite its importance in designing appropriate experimental sampling strategies. As preparation for a farm-scale agro-ecosystem services monitoring project, the 'North Wyke Farm Platform', there was a need to assess the spatial variability of key soil chemical and physical properties. METHODS: the field-scale spatial variability of soil chemical (total N, total C, soil organic matter), soil physical properties (bulk density and particle size distribution) and stable isotope ratios (δ13C and δ15N values) was studied using geostatistical approaches in an intensively managed grassland. RESULTS: the scales over which stable isotopes vary (ranges: 212-258 m) were larger than those of the total nutrients, soil organic matter and bulk density (ranges: 84-170 m). Two visually and statistically distinct areas of Great Field (north and south) were identified in terms of co-occurring high/low values of several soil properties. CONCLUSIONS: the resulting patterns of spatial variability suggest lower spatial variability of stable isotopes than that of total nutrients, soil organic matter and bulk density. Future sampling regimes should be conducted in a grid with 5 years) on the patterns of spatial variability. Copyright © 2012 John Wiley & Sons, Ltd.
Abstract.
Quinton JN, Krueger T, Freer J, Brazier RE, Bilotta GS (2011). A Case Study of Uncertainty: Applying GLUE to EUROSEM. , 80-97.
Deasy C, Baxendale SA, Ridall G, Heathwaite AL, Hodgkinson R, Brazier RE (2011). Advancing understanding of runoff and sediment transfers in agricultural catchments. through simultaneous observations across scales. Earth Surface Processes and Landforms
Beven KJ, Brazier RE (2011). Dealing with uncertainty in erosion model predictions. , 52-79.
Cerda A, Brazier RE, de Vente J, Nearing MA (2011). Scales and erosion. Catena
Brazier RE, Hutton CJ, Parsons AJ, Wainwright J (2011). Scaling Soil Erosion Models in Space and Time. , 98-116.
Bilotta G, Brazier RE, Krueger T, Butler P, Freer J, Hawkins J, Macleod CJA, Haygarth PM, Quinton J (2010). Assessing Catchment-Scale Erosion and Yields of Suspended Solids from Improved Temperate Grassland. Journal of Environmental Monitoring
Granger S, Bol R, Dixon L, Naden P, Old G, Marsh J, Brazier RE, Bilotta G, White S, Haygarth PM, et al (2010). Assessing multiple novel tracers to improve the understanding of the contribution of agricultural farm waste to diffuse water pollution. Journal of Environmental Monitoring
Turnbull L, Brazier RE, Wainwright J (2010). Biotic and abiotic changes in ecosystem structure over a shrub-encroachment gradient in the southwestern USA. Ecosystems
Turnbull L, Wainwright J, Brazier RE (2010). Changes in hydrology and erosion over a transition from grassland to shrubland.
HYDROL PROCESS,
24(4), 393-414.
Abstract:
Changes in hydrology and erosion over a transition from grassland to shrubland
The degradation of grasslands is a common problem across semi-arid areas worldwide. Over the last 150 years, much of the south-western United States has experienced significant land degradation, with desert grasslands becoming dominated by shrubs and concurrent changes in runoff and erosion which are thought to propagate further the process of degradation. Plot-based experiments to determine how spatio-temporal characteristics of soil moisture, runoff and erosion change over a transition from grassland to shrubland were carried out at four sites over a transition from black grama (Bouteloua eriopoda) grassland to creosotebush (Larrea tridentata) shrubland at the Sevilleta NWR LTER site in New Mexico. Each site consisted of a 10 x 30 m bounded runoff plot and adjacent characterization plots with nested sampling points where soil moisture content was measured. Results show distinct spatio-temporal variations in soil moisture content, which are due to the net effect of processes operating at multiple spatial and temporal scales, such as plant uptake of water at local scales versus the redistribution of water during runoff events at the hillslope scale. There is an overall increase in runoff and erosion over the transition from grassland to shrubland, which is likely to be associated with an increase in connectivity of bare, runoff-generating areas, although these increases do not appear to follow a linear trajectory. Erosion rates increased over the transition from grassland to shrubland, likely related in part to changes in runoff characteristics and the increased capacity of the runoff to detach, entrain and transport sediment. Over all plots, fine material was preferentially eroded which has potential implications for nutrient cycling since nutrients tend to be associated with fine sediment. Copyright (C) 2009 John Wiley & Sons, Ltd.
Abstract.
Granger SJ, Hawkins JMB, Bol R, White SM, Naden P, Old G, Bilotta GS, Brazier RE, MacLeod CJA, Haygarth PM, et al (2010). High temporal resolution monitoring of multiple pollutant responses in drainage from an intensively managed grassland catchment caused by a summer storm.
Water, Air, and Soil Pollution,
205(1-4), 377-393.
Abstract:
High temporal resolution monitoring of multiple pollutant responses in drainage from an intensively managed grassland catchment caused by a summer storm
This work presents data on a suite of diffuse pollutants, monitored in a stream draining an intensively managed grassland on a 30 min time step during a period of intense rainfall to better understand their sources and pathways. Nitrite (92 μg l-1), particulate phosphorus (107 μg l -1) and soluble phosphorus (74 μg l-1) exceeded environmental limits during base flow. Concentrations of nitrate and nitrite were decreased during the storm event, whereas all other pollutants generally increased and exceeded environmental limits where specified, especially when associated with a small subsidiary hydrograph on the rising limb of the main hydrograph. Total pollutants loads, when using a 60 min sampling frequency, would have led to significant over and under-estimations depending on which 60 min sample set was used. In the worst case, loads of ammonium could have been under-estimated by 35% or over estimated by 25% with errors being associated with loads on the rising limb of the hydrograph and more specifically a small subsidiary hydrograph. This subsidiary hydrograph may have occurred as a result of runoff from the farm hard standings within the catchment. Incidental transfer of pollutants associate with this runoff have masked the overall grassland pollutant response. To better understand these different source areas and pollutant dynamics, there is a need for novel tracing techniques to elucidate their relative contribution and pathways. © 2009 Springer Science+Business Media B.V.
Abstract.
Turnbull L, Wainwright J, Brazier RE (2010). Hydrology, erosion and nutrient transfers over a transition from semi-arid grassland to shrubland in the South-Western USA: a modelling assessment.
Journal of Hydrology,
388(3-4), 258-272.
Abstract:
Hydrology, erosion and nutrient transfers over a transition from semi-arid grassland to shrubland in the South-Western USA: a modelling assessment
Land degradation in arid and semi-arid areas, as a consequence of the invasion of grasslands by shrubs, is often associated with an increase in runoff and erosion and a change in nutrient transport. Modelling of nutrient transport during runoff events (in particular particulate-bound nutrients), is especially important, since the spatial redistribution of nutrients (in addition to water and sediment) can have significant implications for vegetation dynamics in these ecosystems. In this study, Mahleran (Model for Assessing Hillslope to Landscape Erosion Runoff, and Nutrients) is extensively evaluated against runoff and erosion data from four plots (representative of different stages of land degradation) over a transition from grassland to shrubland, at the Sevilleta National Wildlife Refuge in New Mexico, USA. A new particulate-bound nutrient module was developed to include a representation of particulate-bound nutrient dynamics, which is an important form of nutrient transport in these ecosystems. Understanding dynamics of both dissolved and particulate-bound nutrient dynamics during runoff events is imperative, because of their differing roles in terms of nutrient bioavailability and potential implications for plant dynamics. Results of the model evaluation show that the runoff and erosion components of Mahleran perform reasonably well, as does the new particulate-bound nutrient sub-model, though not consistently. Performance of the particulate-bound nutrient model was better for the end-member plots, because of better parameterization data available for end-member vegetation types. Since the particulate-bound nutrient sub-model is by necessity strongly dependent on the simulated erosion rate, the performance of the particulate-bound nutrient model is dependent on the performance of the erosion component of Mahleran, so that when erosion is well represented by the model, so typically are particulate nutrient transfers. The performance of the dissolved nutrient component of Mahleran was poor in this application, which indicates that the process representation for this semi-arid environment and the parameterisation of the dissolved nutrient component were inadequate. Results from the model evaluation suggest that an improved understanding of dissolved nutrient dynamics during runoff events and simulation if inter-event nutrient dynamics is required, in order to improve the level of process representation within modelling approaches and thus the ability to simulate dissolved nutrient dynamics and their subsequent effects on other ecosystem processes. © 2010 Elsevier B.V. All rights reserved.
Abstract.
Wainwright J, Tunrbull L, Ibrahim TG, Lexartza-Artza I, Thornton SF, Brazier RE (2010). Linking Environmental Régimes, Space and Time: Interpretations of Structural and Functional Connectivity. Geomorphology
Turnbull L, Wainwright J, Brazier RE (2010). Nitrogen and Phosphorus dynamics during runoff events over a transition from grassland to shrubland in South Western USA. Hydrological Processes
Wainwright J, Parsons AJ, Müller EN, Brazier RE, Powell DM (2010). Standing Proud: a Response to “Soil-Erosion Models: Where do we Really Stand?” by Smith et al. Earth Surface Processes and Landforms
Krueger T, Quinton J, Freer J, Macleod CJA, Bilotta GS, Brazier RE, Butler P, Granger S, Haygarth PM (2009). Ensemble evaluation of hydrological model hypotheses. Water Resources Research
Deasy C, Brazier RE, Heathwaite AL, Hodgkinson R (2009). Pathways of runoff and sediment transfer in small agricultural catchments. Hydrological Processes, 23((9)), 1349-1358.
Wainwright J, Parsons AJ, Müller EN, Brazier RE, Powell DM (2009). Response to Hairsine's and Sander's Comment on 'A transport-distance based approach to scaling erosion rates:' Parts 1, 2 and 3 by Wainwright et al. 2008. Earth Surface Processes and Landforms
wainwright J, parsons A, Brazier RE, Muller EN, Powell DM (2009). Response to Hairsine’s and Sander’s ‘Comment
on “A transport-distance based approach to
scaling erosionrates”: Parts 1, 2 and 3 by
Wainwright et al.’. Earth Surface Processes and Landforms
Wainwright J, Parsons AJ, Müller EN, Brazier RE, Powell DM (2009). Response to Kinnell's 'Comment on "A transport-distance approach to scaling erosion rates: III. Evaluating scaling characteristics of Mahleran"'. Earth Surface Processes and Landforms, 34(9), 1320-1321.
Krueger T, Quinton JN, Freer J, Macleod CJA, Bilotta GS, Brazier RE, Butler P, Haygarth PM (2009). Uncertainties in data and models to describe event dynamics of agricultural sediment and phosphorus transfer.
J Environ Qual,
38(3), 1137-1148.
Abstract:
Uncertainties in data and models to describe event dynamics of agricultural sediment and phosphorus transfer.
Mathematical models help to quantify agricultural sediment and phosphorus transfers and to simulate mitigation of pollution. This paper develops empirical models of the dominant sediment and phosphorus event dynamics observed at high resolution in a drained and undrained, intensive grassland field-scale lysimeter (1 ha) experiment. The uncertainties in model development and simulation are addressed using Generalized Likelihood Uncertainty Estimation. A comparison of suspended solids (SS) and total phosphorus (TP) samples with a limited number of manual repeats indicates larger data variability at low flows. Quantitative uncertainty estimates for discharge (Q) are available from another study. Suspended solids-discharge (SS-Q) hysteresis is analyzed for four events and two drained and two undrained fields. Hysteresis loops differ spatially and temporally, and exhaustion is apparent between sequential hydrograph peaks. A coherent empirical model framework for hysteresis, where SS is a function of Q and rate of change of Q, is proposed. This is evaluated taking the Q uncertainty into account, which can contribute substantially to the overall uncertainty of model simulations. The model simulates small hysteresis loops well but fails to simulate exhaustion of SS sources and flushing at the onset of events. Analysis of the TP-SS relationship reveals that most of the variability occurs at low flows, and a power-law relationship can explain the dominant behavior at higher flows, which is consistent across events, fields, and pathways. The need for further field experiments to test hypotheses of sediment mobilization and to quantify data uncertainties is identified.
Abstract.
Author URL.
Turnbull L, Wainwright J, Brazier RE (2008). A conceptual framework for understanding semi-arid land degradation: ecohydrological interactions across multiple-space and time scales.
ECOHYDROLOGY,
1(1), 23-34.
Abstract:
A conceptual framework for understanding semi-arid land degradation: ecohydrological interactions across multiple-space and time scales
Land degradation is a problem prolific across semi-arid areas worldwide. Despite being a complex process including both biotic and abiotic elements, previous attempts to understand ecosystem dynamics have largely been carried out within disparate disciplines of ecology and hydrology, which has led to significant limitations. Here, an ecohydrological framework is outlined. to provide a new direction for the study of land degradation in semi-arid ecosystem. Unlike other frameworks that draw upon hierarchy theory to provide a board, non-explicit conceptual framework is based upon the explicit linkage of process operating over the continuum of temporal and spatial scales by perceiving the ecosystem as a series of structural and functional connections, within which interactions between biotic and abiotic components of the landscape occur. It is hypothesized that semi-arid land degradation conforms to a cusp-catastrophe model in which the two controlling variables are abiotic structural connectivity and abiotic functional connectivity, which implicitly account for ecosystem resilience, and biotic structural and function connectivity. It is suggest therefore that future research must (1) evaluate how abiotic and biotic function (i.e. water, sediment and nutrient loss/redistribution) vary over grass-shrub transitions and (2) quantify the biotic/abiotic structure over grass-shrub transitions, to (3) determine the interactions between ecosystem structure and function. and interaction/feedbacks between biotic and abiotic components of the ecosystem. Copyright (C) 2008 John Wiley & Sons, Ltd.
Abstract.
Deasy C, Heathwaite AL, Brazier RE (2008). A field methodology for quantifying phosphorus transfer and delivery to streams in first order agricultural catchments.
J HYDROL,
350(3-4), 329-338.
Abstract:
A field methodology for quantifying phosphorus transfer and delivery to streams in first order agricultural catchments
An understanding of the relative importance of different hydrological pathways in phosphorus delivery from land to water is currently constrained by a lack of appropriate methods available to quantify the delivery process. New monitoring tools are needed which will provide a framework for understanding phosphorus (P) transfer and delivery at a range of scales in agricultural catchments. A field methodology incorporating the techniques of event-based, on-site observation and sampling within a flexible, non-plot based structure is described and applied to a first order stream catchment in Southern England, UK. The results show that P transfers to the stream reach monitored were dominated by inputs from one field drain, and that overland flow inputs, despite being directly connected to the stream and containing higher P concentrations (maximum 3708 mu g l(-1)), contributed less to the stream P flux. The processes of P transfer and delivery to the stream were complex, changing both within flow pathways and temporally over an event. (C) 2007 Elsevier B.V. All rights reserved.
Abstract.
Wainwright J, Parsons AJ, Muller EN, Brazier RE, Powell DM, Fenti B (2008). A transport-distance approach to scaling erosion rates: 2. Sensitivity and evaluation of MAHLERAN.
EARTH SURF PROC LAND,
33(6), 962-984.
Abstract:
A transport-distance approach to scaling erosion rates: 2. Sensitivity and evaluation of MAHLERAN
In the first paper in this series, we demonstrated that most process-based erosion models have a series of in-built assumptions that led us to question their true process basis. An alternative soil-erosion model (MAHLERAN - Model for Assessing Hilislope-Landscape Erosion, Runoff and Nutrients) based upon particle-travel distance has been presented in the first paper in this series and this paper presents the first of two evaluations of the model. Here, a sensitivity analysis shows that the numerical model is consistent with the analytical model of Parsons et al. (2004) and demonstrates that downslope patterns of sediment flux on hillslopes are a complex interaction of rainfall intensity, duration and pattern; hillslope gradient; surface roughness and sediment size. This result indicates that the spatial scaling of sediment transfers on hillslopes is a non-trivial problem and will vary from point to point and from event to event and thus from year to year. The model is evaluated against field data from a rainfall-simulation experiment on an 18 m x 35 m plot for which there are sub-plot-scale data on runoff hydraulics and sediment flux. The results show that the model is capable of reproducing the sedigraph with an overall normalized root-mean-square error of 18-4% and Nash-Sutcliffe efficiency of 0-90. Spatial and temporal patterns of particle-size distributions of the eroded sediment are also reproduced very well, once erosion parameters have been optimized for the specific soil conditions. Copyright (C) 2008 John Wiley & Sons, Ltd.
Abstract.
Wainwright J, Parsons AJ, Muller EN, Brazier RE, Powell DM, Fenti B (2008). A transport-distance approach to scaling erosion rates: 3. Evaluating scaling characteristics of MAHLERAN.
EARTH SURF PROC LAND,
33(7), 1113-1128.
Abstract:
A transport-distance approach to scaling erosion rates: 3. Evaluating scaling characteristics of MAHLERAN
In the two previous papers of this series, we demonstrated how a novel approach to erosion modelling (MAHLERAN - Model for Assessing Hillslope-Landscape Erosion, Runoff and Nutrients) provided distinct advantages in terms of process representation and explicit scaling characteristics when compared with existing models. A first evaluation furthermore demonstrated the ability of the model to reproduce spatial and temporal patterns of erosion and their particle-size characteristics on a large rainfall-simulation plot. In this paper, we carry out a more detailed evaluation of the model using monitored erosion events on plots of different size. The evaluation uses four plots of 2101, 115.94, 56.84 and 302.19 m(2), with lengths of 4.12, 14.48, 18.95 and 27.78 m, respectively, on similar soils to the rainfall-simulation plot, for which runoff and erosion were monitored under natural rainfall. Although the model produces the correct ranking of the magnitude of erosion events, it performs less well in reproducing the absolute values and particle-size distributions of the eroded sediment. The implications of these results are evaluated in terms of requirements for process understanding and data for parameterization of improved soil-erosion models. We suggest that there are major weaknesses in the current understanding and data underpinning existing models. Consequently, a more holistic re-evaluation is required that produces functional relationships for different processes that are mutually consistent, and that have appropriate parameterization data to support their use in a wide range of environmental conditions. Copyright (C) 2008 John Wiley & Sons, Ltd.
Abstract.
Wainwright J, Parsons AJ, Muller EN, Brazier RE, Powel DM, Fenti B (2008). A transport-distance approach to scaling erosion rates: I. Background and model development.
EARTH SURF PROC LAND,
33(5), 813-826.
Abstract:
A transport-distance approach to scaling erosion rates: I. Background and model development
The process basis of existing soil-erosion models is shown to be ill-founded. The existing literature builds directly or indirectly on Bennett's (1974) paper, which provided a blueprint for integrated catchment-scale erosion modelling. Whereas Bennett recognized the inherent assumptions of the approach suggested, subsequent readings of the paper have led to a less critical approach. Most notably, the assumption that sediment movement could be approximated by a continuity equation that related to transport in suspension has produced a series of submodels that assume that all movement occurs in suspension. For commonly occurring conditions on hilislopes, this case is demonstrably untrue both on theoretical grounds and from empirical observations. Elsewhere in the catchment system, it is only partially true, and the extent to which the assumption is reasonable varies both spatially and temporally. A second ground-breaking paper - that of Foster and Meyer (1972) - was responsible for subsequent uncritical application of a first-order approximation to deposition based on steady-state analysis and again a weak empirical basis. We describe in this paper an alternative model (MAHLERAN - Model for Assessing Hillslope-Landscape Erosion, Runoff and Nutrients) based upon particle-travel distance that overcomes existing limitations by incorporating parameterizations of the different detachment and transport mechanisms that occur in water erosion in hilislopes and small catchments. In the second paper in the series, we consider the sensitivity and general behaviour of MAHLERAN, and test it in relation to data from a large rainfall-simulation experiment. The third paper of the sequence evaluates the model using data from plots of different sizes in monitored rainfall events. From this evaluation, we consider the scaling characteristics of the current form of MAHLERAN and suggest that integrated modelling, laboratory and field approaches are required in order to advance the state of the art in soil-erosion modelling. Copyright (c) 2008 John Wiley & Sons, Ltd.
Abstract.
Parsons AJ, Wainwright J, Brazier RE, Powell DM (2008). Is sediment delivery a fallacy? Reply. Earth Surface Processes and Landforms, 33(10), 1630-1631.
Quinton JN, Brazier RE (2008). Letter to the Editor. SOIL USE MANAGE, 24(4), 427-428.
Bilotta GS, Brazier RE, Haygarth PM, Macleod CJA, Butler P, Granger S, Krueger T, Freer J, Quinton J (2008). Rethinking the contribution of drained and undrained grasslands to sediment-related water quality problems.
J Environ Qual,
37(3), 906-914.
Abstract:
Rethinking the contribution of drained and undrained grasslands to sediment-related water quality problems.
Grass vegetation has been recommended for use in the prevention and control of soil erosion because of its dense sward characteristics and stabilizing effect on the soil. A general assumption is that grassland environments suffer from minimal soil erosion and therefore present little threat to the water quality of surface waters in terms of sediment and sorbed contaminant pollution. Our data question this assumption, reporting results from one hydrological year of observations on a field-experiment monitoring overland flow, drain flow, fluxes of suspended solids, total phosphorus (TP), and molybdate-reactive phosphorus (
Abstract.
Author URL.
parsons A, wainwright J, Brazier RE, powell D (2008). Scale relationships in hillslope runoff and erosion
Reply. Earth Surface Processes and Landforms, 33, 1637-1638.
Bilotta GS, Brazier RE (2008). Understanding the influence of suspended solids on water quality and aquatic biota.
WATER RES,
42(12), 2849-2861.
Abstract:
Understanding the influence of suspended solids on water quality and aquatic biota
Over the last 50 years the effects of suspended solids (SS) on fish and aquatic life have been studied intensively throughout the world. It is now accepted that SS are an extremely important cause of water quality deterioration leading to aesthetic issues, higher costs of water treatment, a decline in the fisheries resource, and serious ecological degradation of aquatic environments. As such, government-led environmental bodies have set recommended water quality guidelines for concentrations of SS in freshwater systems. However, these reference values are often spurious or based on the concept of turbidity as a surrogate measure of the concentration of SS. The appropriateness of these recommended water quality values is evaluated given: (1) the large variability and uncertainty in data available from research describing the effects of SS on aquatic environments, (2) the diversity of environments that these values are expected to relate to, and (3) the range of conditions experienced within these environments. Furthermore, we suggest that reliance solely upon turbidity data as a surrogate for SS must be treated with caution, as turbidity readings respond to factors other than just concentrations of SS, as well as being influenced by the particle-size distribution and shape of SS particles. in addition, turbidity is a measure of only one of the many detrimental effects, reviewed in this paper, which high levels of SS can have in waterbodies. in order to improve the understanding of the effects of SS on aquatic organisms, this review suggests that: First, high-resolution turbidity monitoring should be supplemented with direct, measurements of SS (albeit at lower resolution due to resource issues). This would allow the turbidity record to be checked and calibrated against SS, effectively building a rating-relationship between SS and turbidity, which would in-turn provide a clearer picture of the exact magnitude of the SS problem. Second, SS should also be characterised in terms of their particle-size distribution and chemical composition. This would provide information to develop a more comprehensive understanding of the observed variable effects of a given concentration of SS in aquatic habitats. These two suggested improvements, combined with lower-resolution concurrent measures of aquatic ecological status, would improve our understanding of the effects of SS in aquatic environments and together with a more detailed classification of aquatic environments, would provide an environment-specific evidence base for the establishment of effective water quality guidelines for SS. (C) 2008 Elsevier Ltd. All rights reserved.
Abstract.
Turnbull L, Brazier RE, Wainwright J, Dixon L, Bol R (2008). Use of carbon isotope analysis to understand semi-arid erosion dynamics and long-term semi-arid land degradation.
RAPID COMMUNICATIONS IN MASS SPECTROMETRY,
22(11), 1697-1702.
Abstract:
Use of carbon isotope analysis to understand semi-arid erosion dynamics and long-term semi-arid land degradation
Many semi-arid areas worldwide are becoming degraded, in the form of C-4 grasslands being replaced by C-3 shrublands, which causes an increase in surface runoff and erosion, and altered nutrient cycling, which may affect global biogeochemical cycling. The prevention or control of vegetation transitions is hindered by a lack of understanding of their temporal and spatial dynamics, particularly in terms of interactions between biotic and abiotic processes. This research investigates (1) the effects of soil erosion on the delta C-13 values of soil organic matter (SOM) throughout the soil profile and its implications for reconstructing vegetation change using carbon-isotope analysis and (2) the spatial properties of erosion over a grass-shrub transition to increase understanding of biotic-abiotic interactions by using delta C-13 signals of eroded material as a sediment tracer. Results demonstrate that the soils over grass-shrub transitions are not in steady state. A complex interplay of factors determines the input of SOM to the surface horizon of the soil and its subsequent retention and turnover through the soil profile. A positive correlation between event runoff and delta C-13 signatures of eroded sediment was found in all plots. This indicates that the delta C-13 signatures of eroded sediment may provide a means of distinguishing between changes in erosion dynamics over runoff events of different magnitudes and over different vegetation types. The development of this technique using delta C-13 signatures of eroded sediment provides a new means of furthering existing understanding of erosion dynamics over vegetation transitions. This is critical in terms of understanding biotic-abiotic feedbacks and the evolution of areas subject to vegetation change in semi-arid environments. Copyright (C) 2008 John Wiley & Sons, Ltd.
Abstract.
Brazier RE, Bilotta GS, Haygarthz PM (2007). A perspective on the role of lowland, agricultural grasslands in contributing to erosion and water quality problems in the UK. EARTH SURF PROC LAND, 32(6), 964-967.
Bilotta GS, Brazier RE, Haygarth PM (2007). Processes affecting transfer of sediment and colloids, with associated phosphorus, from intensively farmed grasslands: Erosion. Hydrological Processes, 21(1), 135-139.
Deasy C, Brazier RE, Heathwaite AL, Hodgkinson R (2007). Scale-related sediment and phosphorus transfers in small agricultural catchments.
IAHS-AISH Publication(314), 79-89.
Abstract:
Scale-related sediment and phosphorus transfers in small agricultural catchments
Abstract Gaining a better understanding of the processes and linkages operating in agricultural catchments is essential in understanding how diffuse sources of pollution influence the water quality of fluvial systems. One of the key limitations is the lack of available data at a range of spatial scales, which is necessary in order to improve process understanding and model develop ment. Carefully designed field-based research has the potential to improve predictions of water quality in agricultural catchments, which is particularly important given the context of changing climate and land use. Event-based fluxes of sediment and phosphorus were monitored at different scales in a first-order agricultural catchment in Herefordshire, UK, and the data have enabled characterisation of their behaviour and identification of relationships at various scales from hillslope patches of 60 m length to a 30 ha first-order catchment. The results shown here indicate the differing behaviour of both sediment and phosphorus over six events throughout two hydrological years between two scales of observation: the hillslope and the catchment. Copyright © 2007 IAHS Press.
Abstract.
Powell DM, Brazier R, Parsons A, Wainwright J, Nichols M (2007). Sediment transfer and storage in dryland headwater streams.
GEOMORPHOLOGY,
88(1-2), 152-166.
Abstract:
Sediment transfer and storage in dryland headwater streams
This study describes the dynamics of sediment transfer and storage in three headwater channels of the Walnut Gulch Watershed in the Chihuahuan Desert, southeastern Arizona, USA. Spatially distributed information on volumes of stream-bed scour and fill and the resultant net changes in sediment storage was collected from three channel reaches using dense arrays of scour chains. Reach-averaged estimates of volumetric scour for individual events ranged between 0.001 and 0.11 m(3) m(-2). Scour volumes combine with relatively little scatter when rated against peak unit stream power demonstrating that flood magnitude accounts for much of the variance. As a result of locally compensating scour and fill, net changes in sediment storage during individual events were small. Because aggradation and degradation fluctuated with no persistent temporal trend over the study period, sediment transfers through the reaches were not significantly affected by movement of sediment into or out of storage. Measurements of the volume of sediment trapped in a stock-pond downstream of the study sites suggest that scoured bed material travelled several hundred m year(-1) with a virtual velocity of about 350 m h(-1). (C) 2006 Elsevier B.V. All rights reserved.
Abstract.
Bilotta GS, Brazier RE, Haygarth PM (2007). The Impacts of Grazing Animals on the Quality of Soils, Vegetation, and Surface Waters in Intensively Managed Grasslands.
Advances in Agronomy,
94, 237-280.
Abstract:
The Impacts of Grazing Animals on the Quality of Soils, Vegetation, and Surface Waters in Intensively Managed Grasslands
This chapter provides a comprehensive review of the literature relating to the impacts of grazing animals on the quality of soils, vegetation, and surface waters. It focuses on intensively managed grasslands where there is the greatest potential for these impacts to be observed. The chapter indicates that while well-managed grazing can be beneficial to the environment, intensively managed grazing can actually lead to the degradation of both the soil and vegetation of grassland environments. The various causes, forms, and consequences of this degradation are discussed in detail, and gaps in the knowledge are identified. The chapter highlights the need for recognition and quantification of the relationships between the on-site impacts of grazing animals (i.e. changes in soil properties and vegetation cover) and the off-site impacts of grazing animals (i.e. the impact of these changes on hydrology and water quality in surface waters), as these relationships have, in the past, only been alluded to by authors. However, there exists relatively little research evidence to support and quantify these relationships, thus herein we describe data required to address the lack of understanding of the role of grazing animals on grasslands. Finally, the last section of this chapter considers the land management and remediation options available for the reduction of the impacts of intensive livestock farming. © 2006 Elsevier Inc. All rights reserved.
Abstract.
Brazier RE, Parsons AJ, Powell DM, Wainwright J (2007). Upscaling understanding of nitrogen dynamics associated with overland flow in a semi-arid environment. Biogeochemistry, 82(3), 265-278.
Liu S, Butler D, Brazier R, Heathwaite L, Khu ST (2007). Using genetic algorithms to calibrate a water quality model.
Sci Total Environ,
374(2-3), 260-272.
Abstract:
Using genetic algorithms to calibrate a water quality model.
With the increasing concern over the impact of diffuse pollution on water bodies, many diffuse pollution models have been developed in the last two decades. A common obstacle in using such models is how to determine the values of the model parameters. This is especially true when a model has a large number of parameters, which makes a full range of calibration expensive in terms of computing time. Compared with conventional optimisation approaches, soft computing techniques often have a faster convergence speed and are more efficient for global optimum searches. This paper presents an attempt to calibrate a diffuse pollution model using a genetic algorithm (GA). Designed to simulate the export of phosphorus from diffuse sources (agricultural land) and point sources (human), the Phosphorus Indicators Tool (PIT) version 1.1, on which this paper is based, consisted of 78 parameters. Previous studies have indicated the difficulty of full range model calibration due to the number of parameters involved. In this paper, a GA was employed to carry out the model calibration in which all parameters were involved. A sensitivity analysis was also performed to investigate the impact of operators in the GA on its effectiveness in optimum searching. The calibration yielded satisfactory results and required reasonable computing time. The application of the PIT model to the Windrush catchment with optimum parameter values was demonstrated. The annual P loss was predicted as 4.4 kg P/ha/yr, which showed a good fitness to the observed value.
Abstract.
Parsons AJ, Wainwright J, Brazier RE (2006). A conceptual model for sediment and nutrient fluxes from rural land. International Journal of Biodiversity Science and Management, 2, 1-3.
Parsons AJ, Brazier RE, Wainwright J (2006). A conceptual model for sediment and nutrient fluxes from rural land. International Journal of Biodiversity Science and Management, 2(3), 232-234.
Parsons AJ, Wainwright J, Brazier RE, Powell DM (2006). Is sediment delivery a fallacy?. Earth Surface Processes and Landforms, 31, 1325-1328.
Haygarth PM, Bilotta GS, Bol R, Brazier RE, Butler PJ, Freer J, Gimbert LJ, Granger SJ, Krueger T, Macleod CJA, et al (2006). Processes affecting transfer of sediment and colloids, with associated phosphorus, from intensively farmed grasslands: an overview of key issues.
Hydrological Processes,
20(20), 4407-4413.
Abstract:
Processes affecting transfer of sediment and colloids, with associated phosphorus, from intensively farmed grasslands: an overview of key issues
We consider that here are four key issues and priorities for hydrological sciences in respect to sidement, phosphorus and colloid transfers from intensive grasslands (Table I). These are inadequate inventories, analytical challenges, the neglected role of organic matter and challenges for modelling and integration. We need to change the way in which grassland systems are perceived and monitored; this commentary and the ones that follow may help start to achieve this. There is also a critical requirement for a wider acceptance of a 'continuum' of sediment and particles and processes from molecular to >1 μm, including clarity with operational definitions and an acceptance of the strenghts and weakness of analytical tools. A variety of new tracer techniques are avaliable for helping assess the role of organic matter in contributing to transfers and these must be applied. Field scientists must fully appreciate the variability of observations, and modellers need to understand the uncertainty in model processes and model outputs. Overall, however, the critical message is that integrated inter-disciplinary team working is encourage, discipline polarization is discourage because it undermines progress. To that end, in the assembly of commentaries that follow (Bilotta et al. 2007; Gimbert et al. 2007; Granger et al.; 2007; Krueger et al. 2007) we are presenting ideas as part of an integrated project team that is attempting to improve our knowledge and ability to model sediment, colloids and phosphorus losses from intensive grassland, with - we hope - some wider generic relevance for the hydrological community. Copyright © 2006 John Wiley & Sons, Ltd.
Abstract.
Parsons AJ, Brazier RE, Powell DM, Wainwright J (2006). Scale relationships in hillslope runoff and erosion. Earth Surface Processes and Landforms, 31(11), 1384-1393.
Powell DM, Brazier RE, Wainwright J, Parsons AJ (2006). Spatial patterns of streambed scour, fill and channel change in sand-bed rivers. Water Resources Research, 42
Heathwaite AL, Brazier RE, Dils R, Liu S, Carvahlo L, Pope L, Phillips G, May L (2005). A tiered risk assessment approach to predicting diffuse agricultural phosphorus losses. Science of the Total Environment,, 344, 225-239.
Heathwaite AL, Dils RM, Liu S, Carvalho L, Brazier RE, Pope L, Hughes M, Phillips G, May L (2005). A tiered risk-based approach for predicting diffuse and point source phosphorus losses in agricultural areas.
Science of the Total Environment,
344(1-3 SPEC. ISS.), 225-239.
Abstract:
A tiered risk-based approach for predicting diffuse and point source phosphorus losses in agricultural areas
Implementation of the European Union Water Framework Directive requires an assessment of the pressures from human activity, which, combined with information on the sensitivity of the receiving waterbody to the pressures, will identify those water bodies at risk of failing to meet the Directive's environmental objectives. Part of the process of undertaking the risk assessment for lakes is an assessment of diffuse agricultural phosphorus (P) pressures. Three approaches of increasing sophistication were developed for this purpose: a basic 'risk screening' approach (tier 1) applicable to all lakes in Great Britain (GB) and based on export coefficients for different land cover classes and animal types; the Pressure Delivery Risk Screening Matrix approach (tier 2) that differentiated between pressures in surface water and groundwater river basins; and the Phosphorus Indicators Tool (PIT), a simple model of locational risk and P delivery potential (tier 3). Application of the three approaches to a range of lake catchments in England demonstrated that a tiered risk assessment approach was appropriate which was tailored to the quality of the available data. A step-wise procedure was developed whereby if the tier 1 and 2 approaches showed a catchment to be at high risk of failing to meet the Directive's environmental objectives with regard to P, it was justifiable to undertake a more detailed assessment using the tier 3 approach. The tier 1 approach was applied to all lakes in GB greater than 1 ha in size on the assumption that the boundary between the good/moderate status classes under the Water Framework Directive guidelines represented a doubling of the total P (TP) reference conditions. The initial outputs suggested that 51% of lakes in GB are predicted to not meet the TP targets identified for high or good status and must, therefore, be considered at risk. There were regional differences in numbers of lakes at risk. Scotland appeared to have the fewest sites at risk (18%); England the most (88%), with Wales having an intermediate percentage (56%). A comparison of P pressures on freshwaters using the tier 2 approach with other pressures on waterbodies (e.g. nitrate, sediment) in GB is shown as risk maps on the Environment Agency website at: www.environment-agency.gov.uk/wfdreview. The tier 3 approach was applied to data-rich catchments and identified at the 1 km2 areas of relatively high risk of P delivery to water. © 2005 Elsevier B.V. All rights reserved.
Abstract.
Liu S, Brazier R, Heathwaite L (2005). An investigation into the inputs controlling predictions from a diffuse phosphorus loss model for the UK; the Phosphorus Indicators Tool (PIT).
Science of the Total Environment,
344(1-3 SPEC. ISS.), 211-223.
Abstract:
An investigation into the inputs controlling predictions from a diffuse phosphorus loss model for the UK; the Phosphorus Indicators Tool (PIT)
A simple catchment scale model simulating diffuse phosphorus (P) loss from agricultural land to water, the Phosphorus Indicators Tool (PIT), has been developed. Previous research has shown that this model worked well in simulating the average annual P lost from two catchments: Windermere and Windrush, but it was not known which drivers in the model had the greatest control on predicted P delivery to water from agricultural land. In order to simulate the P export from each catchment source via each hydrological pathway specified individually, 108 coefficients are used in the model code. A univariate sensitivity analysis was conducted to evaluate which coefficient exerted the greatest control on the model output. Results from the univariate analysis suggest that the model is sensitive to a number of coefficients, but importantly, not all of the coefficients that were varied in the sensitivity analysis, altered the model output. The PIT model has been calibrated by optimizing results from the univariate analysis against observed data in the Windermere catchment. The simulated results from model calibration fit the observed data well, at the 95% level. This paper describes the methodology developed for the univariate analysis and evaluates the model calibration procedure against observed data from the Windermere catchment. © 2005 Elsevier B.V. All rights reserved.
Abstract.
Liu S, Brazier RE, Heathwaite AL (2005). An investigation into the inputs controlling predictions from the Phosphorus Indicators Tool (PIT). Science of the Total Environment, 344, 211-223.
Evans R, Brazier RE (2005). Evaluation of spatially distributed predictions of soil erosion by water versus field-based assessments. Environmental Science and Policy, 8, 493-501.
Beven KJ, Brazier RE, Heathwaite AL, Haygarth PM, Walling DE, Withers P (2005). On the concept of delivery of sediment and nutrients to stream channels. Hydrological Processes, 19, 551-556.
Brazier RE, Liu S, Heathwaite AL (2005). Scaling issues relating to P transfer from land to water. Journal of Hydrology, 304, 330-342.
Brazier RE, Parsons AJ, Powell DM, Kaduk J (2005). Streambed scour and fill in low-order dryland channels. Water Resources Research, 41(5).
Parsons AJ, Wainwright J, Powell DM, Brazier RE (2004). A conceptual model for determining soil erosion by water. Earth Surface Processes and Landforms, 29, 1293-1302.
Brazier RE (2004). Quantifying soil erosion by water in the UK; a review of monitoring and modelling approaches. Progress in Physical Geography, 28(3), 1-26.
Brazier RE, Anthony SG, Quinn PF, Rowan JS (2001). "MIRSED" towards an MIR approach to modelling hillslope erosion at the national scale. CATENA, 42(1), 59-79.
Beven, K.J. Anthony, S.G. Rowan, J.S. (2001). Implications of model uncertainty for the mapping of hillslope-scale soil erosion predictions. Earth Surface Processes and Landforms, 26(12), 1333-1352.
Brazier RE, Beven KJ, Freer J, Anthony SG, Rowan J (2000). Equifinality and Uncertainty in physically-based soil erosion models: application of the GLUE methodology to WEPP - the Water Erosion Prediction Project for sites in the UK and US. Earth Surface Processes and Landforms, 25, 825-845.
Chapters
Brazier RE (In Press). Carbon dynamics in dryland systems. In Mueller EN, Parsons AJ, Wainwright J (Eds.) Patterns of land degradation in drylands, Springer.
Hutton C, Brazier RE, Nicholas AN, Nearing MA (In Press). Ephemeral Channel Modelling at Historic timescales in Semi-arid Environments. In (Ed) International Conference on Desertification proceedings, ICOD.
Brazier RE (In Press). Hillslope and soil erosion modelling. In Baas A (Ed) Quantitative Modelling in Geomorphology, Elsevier.
Wainwright J, Brazier RE (In Press). Slope systems. In Thomas DSG (Ed) Arid Zone Geomorphology: Process, Form and Change in Drylands, John Wiley and Sons, Ltd.
Brazier RE (In Press). Uncertainties in field data. In Mueller EN, Parsons AJ, Wainwright J (Eds.) Patterns of land degradation in drylands, Springer.
Brazier RE, Bol R, Dixon E, Turnbull L, Wainwright J (In Press). Understanding the erosion of semi-arid landscapes subject to vegetation change: a combined approach using monitoring and isotope analysis. In (Ed) International Conference on. Desertification (ICOD), ICOD.
Harris P, Howden NJK, Peukert S, Noacco V, Ramezani K, Tuominen E, Eludoyin B, Brazier R, Shepherd A, Griffith B, et al (2016). Contextualized Geographically Weighted Principal Components Analysis for Investigating Baseline Soils Data on the North Wyke Farm Platform. In (Ed) Geostatistical and Geospatial Approaches for the Characterization of Natural Resources in the Environment, Springer Nature, 651-655.
Hochstrasser T, Millington JA, Papanastasis V, Parsons A, Roggero P, Brazier R, Estrany J, Farina A, Puttock A (2014). The Study of Land Degradation in Drylands: State of the Art. In Mueller EN, Wainwright J, Parsons AJ, Turnbull L (Eds.)
Patterns of Land Degradation in Drylands, Springer Netherlands, 13-54.
Author URL.
Brazier RE, Krueger T, Wainwright J (2013). Uncertainty Assessment. In (Ed) Patterns of Land Degradation in Drylands, Springer Nature, 265-285.
Pilgrim ES, Macleod CJA, Blackwell MSA, Bol R, Hogan DV, Chadwick DR, Cardenas L, Misselbrook TH, Haygarth PM, Brazier RE, et al (2010). Chapter four Interactions Among Agricultural Production and Other Ecosystem Services Delivered from European Temperate Grassland Systems. In (Ed) , Elsevier, 117-154.
Beven KJ, Brazier RE (2009). Dealing with uncertainty in soil erosion modelling. In Morgan RPC, Nearing MA (Eds.) The handbook of soil erosion modelling.
Quinton JN, Krueger T, Freer J, Bilotta GS, Brazier RE (2009). EUROSEM: an Evaluation of the dynamic capability of the EUROSEM model using GLUE. In Morgan RPC, Nearing MA (Eds.) The handbook of soil erosion modelling.
Brazier RE, Hutton C, Parsons AJ, Wainwright J (2009). Scaling issues in soil erosion modelling. In Morgan RPC, Nearing MA (Eds.) The handbook of soil erosion modelling.
Brazier R, Schärer M, Heathwaite L, Beven K, Scholefield P, Haygarth P, Hodgkinson R, Walling D, Withers P (2006). A framework for predicting delivery of phosphorus from agricultural land using a decision-tree approach. In (Ed)
, 514-523.
Abstract:
A framework for predicting delivery of phosphorus from agricultural land using a decision-tree approach
Abstract.
Brazier RE, Schärer M, Heathwaite AL, Beven KJ, Scholefield P, Haygarth PM, Walling DE, Withers P, Hodgkinson R (2006). Predicting delivery of phosphorus from agricultural land using a decision-tree approach. In (Ed) IAHS Red Book, Dundee.
Brazier RE, Parsons AJ, Wainwright J, Powell DM, Schlesinger W (2006). Understanding the Effects of Spatial Scale on Nutrient Dynamics Associated with Overland Flow in Semi-Arid Environments. In (Ed) Water management and Soil Conservation in Semi-Arid Environments, International Soil Conservation Organisation.
Wainwright J, Parsons AJ, Powell DM, Brazier RE (2003). A new conceptual framework for understanding and predicting erosion by water from hillslopes and catchments. In II JCA, Flanagan DC (Eds.) Soil Erosion Research for the 21st Century, St Joseph, MI.: American Society of Agricultural Engineers, 607-610.
Powell DM, Brazier RE, Nichols M, Parsons AJ, Wainwright J (2003). Dynamics of scour and fill in ephemeral sand bed channels. In Renard, Kenneth G, McElroy, Stephen A, Gburek, William J, Canfield, Evan H, Scott, Russell L (Eds.) First Interagency Conference on Research in the Watersheds. U.S. Department of Agriculture, Agricultural Research Service, 134-140.
Wainwright J, Brazier RE, Parsons AJ, Michaelides K, Powell DM (2003). Linking short- and long-term soil-erosion modelling. In (Ed) Modelling Approaches for the Rhein LUCIFS Research Framework, Berlin.: Springer Verlag, Berlin.
Conferences
Ashe J, Grand-Clement E, Smith D, Brazier RE, Savic DA (2018). Extracting Value from Complex High-Frequency Multivariate Water Quality Data: Exploring Routinely Collected Operational Data.
Harris P, Howden NJK, Peukert S, Noacco V, Ramezani K, Tuominen E, Eludoyin B, Brazier R, Shepherd A, Griffith B, et al (2014). Contextualized geographically weighted principal components analysis for investigating baseline soils data on the North Wyke Farm Platform.
Abstract:
Contextualized geographically weighted principal components analysis for investigating baseline soils data on the North Wyke Farm Platform
Abstract.
Reports
Brazier RE, Haygarth PM, Macleod CJA, Butler P, Hawkins J, Worsfold P, Bilotta G, Gimbert L, Granger S, Naden P, et al (2009). Final Report to Defra Project PE0120 – Phosphorus mobilisation with sediment and colloids through drained and undrained grasslands.
Publications by year
In Press
Grand-Clement E, Luscombe DJ, Anderson K, Gatis N, Benaud P, Brazier RE (In Press). Antecedent conditions control carbon loss and downstream water quality from shallow, damaged peatlands. Science of the Total Environment, 493, 961-973.
Brazier RE (In Press). Carbon dynamics in dryland systems. In Mueller EN, Parsons AJ, Wainwright J (Eds.) Patterns of land degradation in drylands, Springer.
Forsmoo J, Anderson K, Macleod C, Wilkinson M, Brazier RE (In Press). Drone-based Structure-from-Motion photogrammetry captures grassland sward height variability. Journal of Applied Ecology
Hutton C, Brazier RE, Nicholas AN, Nearing MA (In Press). Ephemeral Channel Modelling at Historic timescales in Semi-arid Environments. In (Ed) International Conference on Desertification proceedings, ICOD.
Gatis N, Anderson K, Grand-Clement E, Luscombe D, Hartley I, Smith D, Brazier R (In Press). Evaluating MODIS vegetation products using digital images for quantifying local peatland CO2 gas fluxes. Remote Sensing in Ecology and Conservation
Brazier RE (In Press). Hillslope and soil erosion modelling. In Baas A (Ed) Quantitative Modelling in Geomorphology, Elsevier.
Grand-Clement E, Anderson K, Smith D, Angus M, Luscombe D, Gatis N, Bray L, Brazier R (In Press). NEW APPROACHES TO THE RESTORATION OF SHALLOW MARGINAL PEATLANDS.
Journal of Environmental ManagementAbstract:
NEW APPROACHES TO THE RESTORATION OF SHALLOW MARGINAL PEATLANDS
Globally, the historic and recent exploitation of peatlands through management practices such as agricultural reclamation, peat harvesting or forestry, have caused extensive damage to these ecosystems. Their value is now increasingly recognised, and restoration and rehabilitation programmes are underway to improve some of the ecosystem services provided by peatlands: blocking drainage ditches in deep peat has been shown to improve the storage of water, decrease carbon losses in the long-term, and improve biodiversity. However, whilst the restoration process has benefitted from experience and technical advice gained from restoration of deep peatlands, shallow peatlands have received less attention in the literature, despite being extensive in both uplands and lowlands. Using the experience gained from the restoration of the shallow peatlands of Exmoor National Park (UK), and two test catchments in particular, this paper provides technical guidance which can be applied to the restoration of other shallow peatlands worldwide. Experience showed that integrating knowledge of the historical environment at the planning stage of restoration was essential, as it enabled the effective mitigation of any threat to archaeological features and sites. The use of bales, commonly employed in other upland ecosystems, was found to be problematic. Instead, ‘leaky dams’ or wood and peat combination dams were used, which are both more efficient at reducing and diverting the flow, and longer lasting than bale dams. Finally, an average restoration cost (£306 ha-1) for Exmoor, below the median national value across the whole of the UK, demonstrates the cost-effectiveness of these techniques. However, local differences in peat depth and ditch characteristics (i.e. length, depth and width) between sites affect both the feasibility and the cost of restoration. Overall, the restoration of shallow peatlands is shown to be technically viable; this paper provides a template for such process over analogous landscapes.
Abstract.
Wainwright J, Brazier RE (In Press). Slope systems. In Thomas DSG (Ed) Arid Zone Geomorphology: Process, Form and Change in Drylands, John Wiley and Sons, Ltd.
Glendell M, Macshane G, Farrow L, Quinton J, Anderson K, Evans M, Benaud P, Rawlins B, Morgan D, Jones L, et al (In Press). Testing the utility of structure from motion photogrammetry reconstructions using small unmanned aerial vehicles and ground photography to estimate the extent of upland soil erosion. Earth Surface Processes and Landforms
Gatis N, Luscombe D, Grand-Clement E, Hartley I, Anderson K, Smith DM, Brazier RE (In Press). The effect of drainage ditches on vegetation diversity and CO2 fluxes in a Molinia caerulea dominated peatland. Ecohydrology
Brazier RE (In Press). Uncertainties in field data. In Mueller EN, Parsons AJ, Wainwright J (Eds.) Patterns of land degradation in drylands, Springer.
Brazier RE, Bol R, Dixon E, Turnbull L, Wainwright J (In Press). Understanding the erosion of semi-arid landscapes subject to vegetation change: a combined approach using monitoring and isotope analysis. In (Ed) International Conference on. Desertification (ICOD), ICOD.
2023
Bateman IJ, Anderson K, Argles A, Belcher C, Betts RA, Binner A, Brazier RE, Cho FHT, Collins RM, Day BH, et al (2023). A review of planting principles to identify the right place for the right tree for ‘net zero plus’ woodlands: Applying a place-based natural capital framework for sustainable, efficient and equitable (SEE) decisions.
People and Nature,
5(2), 271-301.
Abstract:
A review of planting principles to identify the right place for the right tree for ‘net zero plus’ woodlands: Applying a place-based natural capital framework for sustainable, efficient and equitable (SEE) decisions
We outline the principles of the natural capital approach to decision making and apply these to the contemporary challenge of very significantly expanding woodlands as contribution to attaining net zero emissions of greenhouse gases. Drawing on the case of the UK, we argue that a single focus upon carbon storage alone is likely to overlook the other ‘net zero plus’ benefits which woodlands can deliver. A review of the literature considers the wide variety of potential benefits which woodlands can provide, together with costs such as foregone alternative land uses. We argue that decision making must consider all of these potential benefits and costs for the right locations to be planted with the right trees. The paper closes by reviewing the decision support systems necessary to incorporate this information into policy and decision making. Read the free Plain Language Summary for this article on the Journal blog.
Abstract.
Auster RE, Puttock AK, Barr SW, Brazier RE (2023). Learning to live with reintroduced species: beaver management groups are an adaptive <i>process</i>.
Restoration Ecology,
31(5).
Abstract:
Learning to live with reintroduced species: beaver management groups are an adaptive process
In anthropogenic landscapes, wildlife reintroductions are likely to result in interactions between people and reintroduced species. People living in the vicinity may have little familiarity with the reintroduced species or associated management, so will need to learn to live with the species in a new state of “Renewed Coexistence.” in England, Eurasian beavers (Castor fiber) are being reintroduced and U.K. Government agencies are currently considering their national approach to reintroduction and management. Early indications are this will include requirement for “Beaver Management Groups” (BMGs) to engage with local stakeholders. This policy paper reports on qualitative research that captured lessons from the governance of two existing BMGs in Devon (south‐west England), drawing on both a prior study and new interview data. Through the analysis, we identified that BMGs are not a fixed structure, but an adaptive process. This consists of three stages (Formation, Functioning, and Future?), influenced by resource availability and national policy direction. We argue that, where they are used, Species‐specific Management Groups could provide a “front line” for the integration of reintroduced species into modern landscapes, but their role or remit could be scaled back over time and integrated into existing structures or partnerships to reduce pressure on limited resources, as knowledge of reintroduced species (such as beaver) grows and its presence becomes “normalized.” There must be sufficient flexibility in forthcoming policy to minimize constraint on the adaptive nature of BMGs and similar groups for other reintroduced species, if they are to facilitate a sustainable coexistence.
Abstract.
Slade G, Fawcett D, Cunliffe AM, Brazier RE, Nyaupane K, Mauritz M, Vargas S, Anderson K (2023). Optical reflectance across spatial scales—an intercomparison of transect-based hyperspectral, drone, and satellite reflectance data for dry season rangeland. Journal of Unmanned Vehicle Systems (JUVS), 11, 1-20.
Gatis N, Benaud P, Anderson K, Ashe J, Grand-Clement E, Luscombe DJ, Puttock A, Brazier RE (2023). Peatland restoration increases water storage and attenuates downstream stormflow but does not guarantee an immediate reversal of long-term ecohydrological degradation.
Sci Rep,
13(1).
Abstract:
Peatland restoration increases water storage and attenuates downstream stormflow but does not guarantee an immediate reversal of long-term ecohydrological degradation.
Peatland restoration is experiencing a global upsurge as a tool to protect and provide various ecosystem services. As the range of peatland types being restored diversifies, do previous findings present overly optimistic restoration expectations? in an eroding and restored upland peatland we assessed short-term (0-4 year) effects of restoration on ecohydrological functions. Restoration significantly reduced discharge from the site, transforming peat pans into pools. These retained surface water over half the time and were deeper during wet periods than before. In the surrounding haggs water tables stabilised, as drawdown during dry conditions reduced, increasing the saturated peat thickness. Despite these changes, there were no effects on photosynthesis, ecosystem respiration or dissolved organic carbon loads leaving the site. Soil respiration did not decrease as water tables rose, but methane emissions were higher from rewet pools. Restoration has had a dramatic effect on hydrology, however, consequent changes in other ecosystem functions were not measured in the 4 years after restoration. Whilst restoration is crucial in halting the expansion of degraded peatland areas, it is vital that practitioners and policymakers advocating for restoration are realistic about the expected outcomes and timescales over which these outcomes may manifest.
Abstract.
Author URL.
Puttock A, Newman M, Graham H, Elliott M, Chant J, Auster R, Brazier R (2023). Positive coexistence of water voles and beaver: water vole expansion in a beaver engineered wetland.
Luscombe DJ, Gatis N, Anderson K, Carless D, Brazier RE (2023). Rapid, repeatable landscape-scale mapping of tree, hedgerow, and woodland habitats (THaW), using airborne LiDAR and spaceborne SAR data.
Ecol Evol,
13(5).
Abstract:
Rapid, repeatable landscape-scale mapping of tree, hedgerow, and woodland habitats (THaW), using airborne LiDAR and spaceborne SAR data.
In the UK, tree, hedgerow, and woodland (THaW) habitats are key havens for biodiversity and support many related ecosystem services. The UK is entering a period of agricultural policy realignment with respect to natural capital and climate change, meaning that now is a critical time to evaluate the distribution, resilience, and dynamics of THaW habitats. The fine-grained nature of habitats like hedgerows necessitates mapping of these features at relatively fine spatial resolution-and freely available public archives of airborne laser scanning (LiDAR) data at 90%. It was also possible to combine LiDAR mapping data and Sentinel-1 SAR data to rapidly track canopy change through time (i.e. every 3 months) using, cloud-based processing via Google Earth Engine. The resultant toolkit is also provided as an open-access web app. The results highlight that whilst nearly 90% of the tallest trees (above 15 m) are captured within the National Forest Inventory (NFI) database only 50% of THaW with a canopy height range of 3-15 m are recorded. Current estimates of tree distribution neglect these finer-grained features (i.e. smaller or less contiguous THaW canopies), which we argue will account for a significant proportion of landscape THaW cover.
Abstract.
Author URL.
Auster RE, Puttock A, Bradbury G, Brazier R (2023). Should individual animals be given names in wildlife reintroductions?.
People and Nature,
5(4), 1110-1118.
Abstract:
Should individual animals be given names in wildlife reintroductions?
Individual animals are often given names by humans. For example, names are attributed to domestic animals to acknowledge their closeness to people, some research studies use names to identify differences between individuals in a study group, or zoos often use names to tell stories that attract public or media attention. Publicly naming individual animals can provide opportunities in conservation, but there are also risks. In this perspective we exemplify such opportunities and risks in the context of wildlife reintroductions. We draw on examples and observations from our experience researching Eurasian beaver Castor fiber reintroduction in England, to encourage careful thinking before publicly attributing a name to an individual in reintroduction projects. Naming individuals in reintroduction can: be a low-cost engagement tool; help people relate to unfamiliar reintroduced species; encourage local ownership of reintroduction projects; enable an effective tool for communicating information about the species and ways to coexist; or support creative or cultural expression. Yet naming individuals in reintroduction could: risk misrepresentation of natural species characteristics; make it challenging to normalise the sense that the reintroduced species is a wild animal; unintentionally imply that humans have ownership or power over the animal; cause distraction from establishing viable populations due to focus on the individual; or result in human investment in individual animals, which may have influence on reintroduction outcomes if that animal later comes to harm or dies (naturally or otherwise). Synthesis and Applications. We argue there is more to the act of naming individuals than may first appear. If considering doing so, we call for careful thought about whether it is appropriate and how to go about it. While we intentionally refrain from concluding whether ‘to name or not to name’, we call for careful, informative, message framing that takes advantage of the opportunities and is prepared for future circumstances, when naming of individuals does take place. Read the free Plain Language Summary for this article on the Journal blog.
Abstract.
Benaud P, Anderson K, James MR, Quine TA, Quinton JN, Brazier RE (2023). Structure-from-Motion Photogrammetry and Rare Earth Oxides can quantify diffuse and convergent soil loss and source apportionment. International Soil and Water Conservation Research, 11(4), 633-648.
Bradbury G, Puttock A, Coxon G, Clarke S, Brazier RE (2023). Testing a novel sonar-based approach for measuring water depth and monitoring sediment storage in beaver ponds.
RIVER RESEARCH AND APPLICATIONS,
39(2), 266-273.
Author URL.
2022
Gatis N, Carless D, Luscombe DJ, Brazier RE, Anderson K (2022). An operational land cover and land cover change toolbox: processing open‐source data with open‐source software.
Ecological Solutions and Evidence,
3(3).
Abstract:
An operational land cover and land cover change toolbox: processing open‐source data with open‐source software
Abstract
Accurate and up‐to‐date land cover maps are vital for underpinning evidence‐based landscape management decision‐making. However, the technical skills required to extract tailored information about land cover dynamics from these open‐access geospatial data often limit their use by those making landscape management decisions.
Using Dartmoor National Park as an example, we demonstrate an open‐source toolkit which uses open‐source software (QGIS and RStudio) to process freely available Sentinel‐2 and public LiDAR data sets to produce fine scale (10 m2 grain size) land cover maps.
The toolbox has been designed for use by staff within the national park, for example, enabling land cover maps to be updated as required in the future.
An area of 945 km2 was mapped using a trained random forest classifier following a classification scheme tailored to the needs of the national park.
A 2019 land cover map had an overall user's accuracy of 79%, with 13 out of 17 land cover classes achieving greater than 70% accuracy.
Spatially, accuracy was related via logistical regression to blue band surface reflectance in the spring and topographic slope derived from LiDAR (1 m resolution), with greater accuracy in steeper terrain and areas exhibiting higher blue reflectance.
Between an earlier (2017–2019) and later (2019–2021) time frame, 8% of pixels changed, most of the change by area occurred in the most common classes. However, the largest proportional increase occurred in Upland Meadows, Lowland Meadows and Blanket Bog, all habitats subject to restoration efforts. Identifying areas of change enables future field work to be better targeted.
We discuss the application of this mapping to land management within the Dartmoor national park and of the potential of tailored land cover and land cover change mapping, via this toolbox, to evidence‐based environmental decision‐making more widely.
Abstract.
Fawcett D, Cunliffe AM, Sitch S, O’Sullivan M, Anderson K, Brazier RE, Hill TC, Anthoni P, Arneth A, Arora VK, et al (2022). Assessing Model Predictions of Carbon Dynamics in Global Drylands.
Frontiers in Environmental Science,
10Abstract:
Assessing Model Predictions of Carbon Dynamics in Global Drylands
Drylands cover ca. 40% of the land surface and are hypothesised to play a major role in the global carbon cycle, controlling both long-term trends and interannual variation. These insights originate from land surface models (LSMs) that have not been extensively calibrated and evaluated for water-limited ecosystems. We need to learn more about dryland carbon dynamics, particularly as the transitory response and rapid turnover rates of semi-arid systems may limit their function as a carbon sink over multi-decadal scales. We quantified aboveground biomass carbon (AGC; inferred from SMOS L-band vegetation optical depth) and gross primary productivity (GPP; from PML-v2 inferred from MODIS observations) and tested their spatial and temporal correspondence with estimates from the TRENDY ensemble of LSMs. We found strong correspondence in GPP between LSMs and PML-v2 both in spatial patterns (Pearson’s r = 0.9 for TRENDY-mean) and in inter-annual variability, but not in trends. Conversely, for AGC we found lesser correspondence in space (Pearson’s r = 0.75 for TRENDY-mean, strong biases for individual models) and in the magnitude of inter-annual variability compared to satellite retrievals. These disagreements likely arise from limited representation of ecosystem responses to plant water availability, fire, and photodegradation that drive dryland carbon dynamics. We assessed inter-model agreement and drivers of long-term change in carbon stocks over centennial timescales. This analysis suggested that the simulated trend of increasing carbon stocks in drylands is in soils and primarily driven by increased productivity due to CO2 enrichment. However, there is limited empirical evidence of this 50-year sink in dryland soils. Our findings highlight important uncertainties in simulations of dryland ecosystems by current LSMs, suggesting a need for continued model refinements and for greater caution when interpreting LSM estimates with regards to current and future carbon dynamics in drylands and by extension the global carbon cycle.
Abstract.
Lockwood T, Freer J, Michaelides K, Brazier RE, Coxon G (2022). Assessing the efficacy of offline water storage ponds for natural flood management. Hydrological Processes, 36(6).
Auster RE, Barr SW, Brazier RE (2022). Beavers and flood alleviation: Human perspectives from downstream communities.
Journal of Flood Risk Management,
15(2).
Abstract:
Beavers and flood alleviation: Human perspectives from downstream communities
AbstractNatural flood management (NFM) methods work with natural processes to reduce flood risk, while often providing additional benefits such as water quality improvement or habitat provision. Increasingly, the activity of an animal—beavers—is recognised to potentially provide flow attenuation, along with multiple benefits for the environment and society, but there can also be associated challenges. We use Q‐Methodology to elicit and understand human perspectives of beavers and their potential role in flood management among communities living downstream of beavers at three sites in England (Cornwall, Yorkshire and the Forest of Dean). This is the first time a study has focused on downstream communities as the primary stakeholders. We identify diverse perspectives that exhibit a range of value judgements. We suggest a catchment‐based approach to beaver management and public engagement may facilitate deeper recognition of contextual perspectives in decision‐making and enable knowledge dissemination with communities. Further, we examine the relationship between beavers and other NFM methods through these perspectives. In doing so we identify features that relate to the unique element of relying on the natural behaviour of beavers for flood management, rather than human flood managers being the primary decision‐makers.
Abstract.
Graham H, Puttock A, Elliott M, Anderson K, Brazier R (2022). Exploring the causes of flow attenuation at a beaver dam sequence.
Abstract:
Exploring the causes of flow attenuation at a beaver dam sequence.
Beavers influence hydrology by constructing woody dams. Using a before
after control impact experimental design, we quantified the effects of a
beaver dam sequence on the flow regime of a stream in SW England.
Building upon our previous research (Puttock et al. 2021), we consider
the mechanisms that underpin flow attenuation in beaver wetlands.
Rainfall-driven hydrological events were extracted between 2009 and
2020, for the impacted (n=612) and control (n=634) catchments, capturing
events seven years before and three years after beaver occupancy, at the
impacted site. General additive models were used to describe average
hydrograph geometry across all events. After beaver occupancy, Lag times
increased by 55.9% and declined by 17.5% in impacted and control
catchments, respectively. Flow duration curve analysis showed a larger
reduction in frequency of high flows, following beaver dam construction,
with declines of Q5 exceedance levels of 33% and 15% for impact and
control catchments, respectively. Using event total rainfall to predict
peak flow, five generalised linear models were fitted to test the
hypothesis that beaver dams attenuate flow, to a greater degree, with
larger storm magnitude. The best performing model showed we can have
high confidence that beaver dams attenuated peak flows, with increasing
magnitude, up to between 0.5-2.5 m. s
for the 94. percentile of event
total rainfall; but we cannot confidently detect attenuation beyond the
97. percentile. Increasing flow attenuation, with
event magnitude, is attributed to transient floodplain storage in low
gradient/profile floodplain valleys. These findings support the
assertion that beaver dams restore attenuated flows. However, with
long-term datasets of extreme hydrological events lacking, it is
challenging to predict the effect of beaver dams during extreme events
with high precision. Beaver dams will have spatially variable impacts on
hydrological processes, requiring further investigation to quantify
responses to dams across differing landscapes and scales.
Abstract.
Graham HA, Puttock AK, Elliott M, Anderson K, Brazier RE (2022). Exploring the dynamics of flow attenuation at a beaver dam sequence. Hydrological Processes, 36(11).
Cunliffe AM, Anderson K, Boschetti F, Brazier RE, Graham HA, Myers-Smith IH, Astor T, Boer MM, Calvo LG, Clark PE, et al (2022). Global application of an unoccupied aerial vehicle photogrammetry protocol for predicting aboveground biomass in non-forest ecosystems.
REMOTE SENSING IN ECOLOGY AND CONSERVATION,
8(1), 57-71.
Author URL.
Ritson JP, Kennedy-Blundell O, Croft J, Templeton MR, Hawkins CE, Clark JM, Evans MG, Brazier RE, Smith D, Graham NJD, et al (2022). High frequency UV-Vis sensors estimate error in riverine dissolved organic carbon load estimates from grab sampling.
Environ Monit Assess,
194(11).
Abstract:
High frequency UV-Vis sensors estimate error in riverine dissolved organic carbon load estimates from grab sampling.
High frequency ultraviolet - visible (UV-VIS) sensors offer a way of improving dissolved organic carbon (DOC) load estimates in rivers as they can be calibrated to DOC concentration. This is an improvement on periodic grab sampling, or the use of pumped sampling systems which store samples in-field before collection. We hypothesised that the move to high frequency measurements would increase the load estimate based on grab sampling due to systemic under-sampling of high flows. To test our hypotheses, we calibrated two sensors in contrasting catchments (Exe and Bow Brook, UK) against weekly grab sampled DOC measurements and then created an hourly time series of DOC for the two sites. Taking this measurement as a 'true' value of DOC load, we simulated 1,000 grab sampling campaigns at weekly, fortnightly and monthly frequency to understand the likely distribution of load and error estimates. We also performed an analysis of daily grab samples collected using a pumped storage sampling system with weekly collection. Our results show that: a) grab sampling systemically underestimates DOC loads and gives positively skewed distributions of results, b) this under-estimation and positive skew decreases with increasing sampling frequency, c) commonly used estimates of error in the load value are also systemically lowered by the oversampling of low, stable flows due to their dependence on the variance in the flow-weighted mean concentration, and d) that pumped storage systems may lead to under-estimation of DOC and over estimation of specific ultra-violet absorbance (SUVA), a proxy for aromaticity, due to biodegradation during storage.
Abstract.
Author URL.
Graham HA, Puttock A, Chant J, Elliott M, Campbell‐Palmer R, Anderson K, Brazier RE (2022). Monitoring, modelling and managing beaver (Castor fiber) populations in the River Otter catchment, Great Britain. Ecological Solutions and Evidence, 3(3).
Auster RE, Barr SW, Brazier RE (2022). Renewed coexistence: learning from steering group stakeholders on a beaver reintroduction project in England.
EUROPEAN JOURNAL OF WILDLIFE RESEARCH,
68(1).
Author URL.
Cunliffe AM, Boschetti F, Clement R, Sitch S, Anderson K, Duman T, Zhu S, Schlumpf M, Litvak ME, Brazier RE, et al (2022). Strong Correspondence in Evapotranspiration and Carbon Dioxide Fluxes Between Different Eddy Covariance Systems Enables Quantification of Landscape Heterogeneity in Dryland Fluxes. Journal of Geophysical Research Biogeosciences, 127(8).
2021
Puttock A, Graham HA, Ashe J, Luscombe DJ, Brazier RE (2021). Beaver dams attenuate flow: a multi-site study.
Hydrological Processes,
35(2).
Abstract:
Beaver dams attenuate flow: a multi-site study
Beavers can profoundly alter riparian environments, most conspicuously by creating dams and wetlands. Eurasian beaver (Castor fiber) populations are increasing and it has been suggested they could play a role in the provision of multiple ecosystem services, including natural flood management. Research at different scales, in contrasting ecosystems is required to establish to what extent beavers can impact on flood regimes. Therefore, this study determines whether flow regimes and flow responses to storm events were altered following the building of beaver dams and whether a flow attenuation effect could be significantly attributed to beaver activity. Four sites were monitored where beavers have been reintroduced in England. Continuous monitoring of hydrology, before and after beaver impacts, was undertaken on streams where beavers built sequences of dams. Stream orders ranged from 2nd to 4th, in both agricultural and forest-dominated catchments. Analysis of >1000 storm events, across four sites showed an overall trend of reduced total stormflow, increased peak rainfall to peak flow lag times and reduced peak flows, all suggesting flow attenuation, following beaver impacts. Additionally, reduced high flow to low flow ratios indicated that flow regimes were overall becoming less “flashy” following beaver reintroduction. Statistical analysis, showed the effect of beaver to be statistically significant in reducing peak flows with estimated overall reductions in peak flows from −0.359 to −0.065 m3 s−1 across sites. Analysis showed spatial and temporal variability in the hydrological response to beaver between sites, depending on the level of impact and seasonality. Critically, the effect of beavers in reducing peak flows persists for the largest storms monitored, showing that even in wet conditions, beaver dams can attenuate average flood flows by up to ca. 60%. This research indicates that beavers could play a role in delivering natural flood management.
Abstract.
Ellis N, Brazier R, Anderson K (2021). Comparing fine‐scale structural and hydrologic connectivity within unimproved and improved grassland.
Ecohydrology,
14(7).
Abstract:
Comparing fine‐scale structural and hydrologic connectivity within unimproved and improved grassland
AbstractGrasslands vary with diverse forms and functions ranging from monocultures of perennial rye grass to more biodiverse unimproved grasslands which cover around 5% of Europe. Despite the broad diversity of grassland types, within environmental and flood risk models grasslands are frequently represented by a singular set of hydrological and structural parameters which belies their diversity and complexity. This study aimed to determine empirically the extent to which improved versus unimproved grasslands exhibit different hydrological connectivity. Working in SW England at neighbouring field sites with comparable slopes and rainfall regimes, we used unpiloted aerial vehicles to survey a tussocky Molinia caerulea dominated unimproved grassland field (MCUG) field and a Lolium perenne dominated improved grassland (LPIG) field. Using digital photogrammetry workflows applied to the overlapping aerial images, we produced a digital surface model (DSM) at 0.03‐m resolution from which flow pathways were modelled using GIS and compared with 1‐m LiDAR and DSM produced by a global navigation satellite system (GNSS). MCUG had longer, tortuous pathways through the dense tussock network with a drainage density of 2.54 m m−2. This was significantly greater than drainage density in the LPIG (1.82 m m−2). As a result of this study, we rescaled the Manning's n value for MCUG according to photogrammetrically‐derived roughness values. We suggest it should lie between 0.075 and 0.09. Our data shows that MCUG can play an important role in reducing overland flow impacts when compared to LPIG through lower connectivity which can delay run‐off to rivers.
Abstract.
Ellis N, Anderson K, Brazier R (2021). Mainstreaming natural flood management: a proposed research framework derived from a critical evaluation of current knowledge.
Progress in Physical Geography: Earth and Environment,
45(6), 819-841.
Abstract:
Mainstreaming natural flood management: a proposed research framework derived from a critical evaluation of current knowledge
Natural flood management (NFM), or working with natural processes, is a growing flood risk management method in the UK, Europe and worldwide. However, unlike the current dominant technical flood management, it lacks an established evidence base of flood risk parameters. This lack of evidence base can limit the uptake of NFM as a flood management method. This paper critically evaluates examples of NFM and wider relevant literature in order to identify NFM knowledge gaps and suggest how to overcome these. The UK is used as a microcosm of different environments for diverse examples. The sections include: land cover, land management, landscape interactions and trade-offs, evaluating the wider benefits of NFM and, finally, scaling from plot to catchment. This concludes in a suggested framework for a new approach to NFM research, which encompasses spatial scales, interactions and trade-offs of NFM and consistency of reporting results. Widening the NFM empirical evidence base should be seen as an opportunity for a new approach to flood research through exploring new habitats and new flood resilience methods.
Abstract.
Benaud P, Anderson K, Evans M, Farrow L, Glendell M, James MR, Quine TA, Quinton JN, Rickson RJ, Brazier RE, et al (2021). Reproducibility, open science and progression in soil erosion research. A reply to “Response to ‘National-scale geodata describe widespread accelerated soil erosion’ Benaud et al. (2020) Geoderma 271, 114378” by Evans and Boardman (2021). Geoderma, 402
Campbell-Palmer R, Puttock A, Wilson KA, Leow-Dyke A, Graham HA, Gaywood MJ, Brazier RE (2021). Using field sign surveys to estimate spatial distribution and territory dynamics following reintroduction of the Eurasian beaver to British river catchments.
RIVER RESEARCH AND APPLICATIONS,
37(3), 343-357.
Author URL.
2020
Cunliffe AM, McIntire CD, Boschetti F, Sauer KJ, Litvak M, Anderson K, Brazier RE (2020). Allometric Relationships for Predicting Aboveground Biomass and Sapwood Area of Oneseed Juniper (Juniperus monosperma) Trees.
Frontiers in Plant Science,
11Abstract:
Allometric Relationships for Predicting Aboveground Biomass and Sapwood Area of Oneseed Juniper (Juniperus monosperma) Trees
Across the semi-arid ecosystems of the southwestern USA, there has been widespread encroachment of woody shrubs and trees including Juniperus species into former grasslands. Quantifying vegetation biomass in such ecosystems is important because semi-arid ecosystems are thought to play an important role in the global land carbon (C) sink, and changes in plant biomass also have implications for primary consumers and potential bioenergy feedstock. Oneseed Juniper (J. monosperma) is common in desert grasslands and pinyon-juniper rangelands across the intermountain region of southwestern North America; however, there is limited information about the aboveground biomass (AGB) and sapwood area (SWA) for this species, causing uncertainties in estimates of C stock and transpiration fluxes. In this study, we report on canopy area, stem diameter, maximum height and biomass measurements from J. monosperma trees sampled from central New Mexico. Dry biomass ranged between 0.4 kg and 625 kg, and cross-sectional sapwood area was measured on n=200 stems using image analysis. We found a strong linear relationship between canopy area and AGB (r2 = 0.96), with a similar slope to that observed in other juniper species, suggesting that this readily measured attribute is well suited for upscaling studies. There was a 9% bias between different approaches to measuring canopy area, indicating care should be taken to account for these differences to avoid systematic biases. We found equivalent stem diameter (ESD) was a strong predictor of biomass, but that existing allometric models under-predicted biomass in larger trees. We found sapwood area could be predicted from individual stem diameter with a power relationship, and that tree-level SWA should be estimated by summing the SWA predictions from individual stems rather than ESD. Our improved allometric models for J. monosperma support more accurate and robust measurements of C storage and transpiration fluxes in Juniperus-dominated ecosystems.
Abstract.
Author URL.
Auster RE, Barr S, Brazier R (2020). Alternative perspectives of the angling community on Eurasian beaver (<i>Castor fiber</i>) reintroduction in the River Otter Beaver Trial. Journal of Environmental Planning and Management, 64(7), 1252-1270.
Brazier RE, Puttock A, Graham HA, Auster RE, Davies KH, Brown CML (2020). Beaver: Nature's ecosystem engineers.
WIREs Water,
8(1).
Abstract:
Beaver: Nature's ecosystem engineers
AbstractBeavers have the ability to modify ecosystems profoundly to meet their ecological needs, with significant associated hydrological, geomorphological, ecological, and societal impacts. To bring together understanding of the role that beavers may play in the management of water resources, freshwater, and terrestrial ecosystems, this article reviews the state‐of‐the‐art scientific understanding of the beaver as the quintessential ecosystem engineer. This review has a European focus but examines key research considering both Castor fiber—the Eurasian beaver and Castor canadensis—its North American counterpart. In recent decades species reintroductions across Europe, concurrent with natural expansion of refugia populations has led to the return of C. fiber to much of its European range with recent reviews estimating that the C. fiber population in Europe numbers over 1.5 million individuals. As such, there is an increasing need for understanding of the impacts of beaver in intensively populated and managed, contemporary European landscapes. This review summarizes how beaver impact: (a) ecosystem structure and geomorphology, (b) hydrology and water resources, (c) water quality, (d) freshwater ecology, and (e) humans and society. It concludes by examining future considerations that may need to be resolved as beavers further expand in the northern hemisphere with an emphasis upon the ecosystem services that they can provide and the associated management that will be necessary to maximize the benefits and minimize conflicts.This article is categorized under:
Water and Life > Nature of Freshwater Ecosystems
Abstract.
Gatis N, Luscombe DJ, Benaud P, Ashe J, Grand-Clement E, Anderson K, Hartley IP, Brazier RE (2020). Drain blocking has limited short-term effects on greenhouse gas fluxes in a Molinia caerulea dominated shallow peatland. Ecological Engineering, 158, 106079-106079.
Cunliffe AM, Anderson K, Boschetti F, Brazier RE, Graham HA, Myers-Smith IH, Astor T, Boer MM, Calvo L, Clark PE, et al (2020). Drone-derived canopy height predicts biomass across non-forest ecosystems globally.
Abstract:
Drone-derived canopy height predicts biomass across non-forest ecosystems globally
AbstractNon-forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, yet are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely-sensed biomass products and are undersampled by in-situ monitoring. Current global change threats emphasise the need for new tools to capture biomass change in non-forest ecosystems at appropriate scales. Here we assess whether canopy height inferred from drone photogrammetry allows the estimation of aboveground biomass (AGB) across low-stature plant species sampled through a global site network. We found mean canopy height is strongly predictive of AGB across species, demonstrating standardised photogrammetric approaches are generalisable across growth forms and environmental settings. Biomass per-unit-of-height was similar within, but different among, plant functional types. We find drone-based photogrammetry allows for monitoring of AGB across large spatial extents and can advance understanding of understudied and vulnerable non-forested ecosystems across the globe.
Abstract.
Auster RE, Barr SW, Brazier RE (2020). Improving engagement in managing reintroduction conflicts: learning from beaver reintroduction. Journal of Environmental Planning and Management, 64(10), 1713-1734.
Graham HA, Puttock A, Macfarlane WW, Wheaton JM, Gilbert JT, Campbell-Palmer R, Elliott M, Gaywood MJ, Anderson K, Brazier RE, et al (2020). Modelling Eurasian beaver foraging habitat and dam suitability, for predicting the location and number of dams throughout catchments in Great Britain.
European Journal of Wildlife Research,
66(3).
Abstract:
Modelling Eurasian beaver foraging habitat and dam suitability, for predicting the location and number of dams throughout catchments in Great Britain
AbstractEurasian beaver (Castor fiber) populations are expanding across Europe. Depending on location, beaver dams bring multiple benefits and/or require management. Using nationally available data, we developed: a Beaver Forage Index (BFI), identifying beaver foraging habitat, and a Beaver Dam Capacity (BDC) model, classifying suitability of river reaches for dam construction, to estimate location and number of dams at catchment scales. Models were executed across three catchments, in Great Britain (GB), containing beaver. An area of 6747 km2 was analysed for BFI and 16,739 km of stream for BDC. Field surveys identified 258 km of channel containing beaver activity and 89 dams, providing data to test predictions. Models were evaluated using a categorical binomial Bayesian framework to calculate probability of foraging and dam construction. BFI and BDC models successfully categorised the use of reaches for foraging and damming, with higher scoring reaches being preferred. Highest scoring categories were ca. 31 and 79 times more likely to be used than the lowest for foraging and damming respectively. Zero-inflated negative binomial regression showed that modelled dam capacity was significantly related (p = 0.01) to observed damming and was used to predict numbers of dams that may occur. Estimated densities of dams, averaged across each catchment, ranged from 0.4 to 1.6 dams/km, though local densities may be up to 30 dams/km. These models provide fundamental information describing the distribution of beaver foraging habitat, where dams may be constructed and how many may occur. This supports the development of policy and management concerning the reintroduction and recolonisation of beaver.
Abstract.
Benaud P, Anderson K, Evans M, Farrow L, Glendell M, James MR, Quine TA, Quinton JN, Rawlins B, Jane Rickson R, et al (2020). National-scale geodata describe widespread accelerated soil erosion.
Geoderma,
371Abstract:
National-scale geodata describe widespread accelerated soil erosion
Accelerated soil erosion can result in substantial declines in soil fertility and has devastating environmental impacts. Consequently, understanding if rates of soil erosion are acceptable is of local and global importance. Herein we use empirical soil erosion observations collated into an open access geodatabase to identify the extent to which existing data and methodological approaches can be used to develop an empirically-derived understanding of soil erosion in the UK (by way of an example). The findings indicate that whilst mean erosion rates in the UK are low, relative to the rest of Europe for example, 16% of observations on arable land were greater than the supposedly tolerable rate of 1 t ha−1 yr−1 and maximum erosion rates were as high as 91.7 t ha−1 yr−1. However, the analysis highlights a skew in existing studies towards locations with a known erosion likelihood and methods that are biased towards single erosion pathways, rather than an all-inclusive study of erosion rates and processes. Accordingly, we suggest that future soil erosion research and policy must address these issues if an accurate assessment of soil erosion rates at the national-scale are to be established. The interactive geodatabase published alongside this paper offers a platform for the simultaneous development of soil erosion research, formulation of effective policy and better protection of soil resources.
Abstract.
Auster RE, Barr SW, Brazier RE (2020). Wildlife tourism in reintroduction projects: Exploring social and economic benefits of beaver in local settings. Journal for Nature Conservation, 58, 125920-125920.
2019
Gatis N, Benaud P, Ashe J, Luscombe D, Grand-Clement E, Hartley I, Anderson K, Brazier R (2019). ASSESSING THE IMPACT OF PEAT EROSION ON GROWING SEASON CO2 FLUXES BY COMPARING EROSIONAL PEAT PANS AND SURROUNDING VEGETATED HAGGS.
Wetlands Ecology and Management, 1-19.
Abstract:
ASSESSING THE IMPACT OF PEAT EROSION ON GROWING SEASON CO2 FLUXES BY COMPARING EROSIONAL PEAT PANS AND SURROUNDING VEGETATED HAGGS
Peatlands are recognised as an important but vulnerable ecological resource. Understanding the effects of existing damage, in this case erosion, enables more informed land management decisions to be made. Over the growing seasons of 2013 and 2014 photosynthesis and ecosystem respiration were measured using closed chamber techniques within vegetated haggs and erosional peat pans in Dartmoor National Park, southwest England. Below-ground total and heterotrophic respiration were measured and autotrophic respiration estimated from the vegetated haggs.
The mean water table was significantly higher in the peat pans than in the vegetated haggs; because of this, and the switching from submerged to dry peat, there were differences in vegetation composition, photosynthesis and ecosystem respiration. In the peat pans photosynthetic CO2 uptake and ecosystem respiration were greater than in the vegetated haggs and strongly dependent on the depth to water table (r2>0.78, p
Abstract.
Gatis NL, Benaud P, Ashe J, Luscombe D, Grand-Clement E, Hartley I, Anderson K, Brazier R (2019). Assessing the impact of peat erosion on growing season CO2 fluxes by comparing erosional peat pans and surrounding vegetated haggs (dataset).
Gatis N, Grand-Clement E, Luscombe DJ, Hartley IP, Anderson K, Brazier RE (2019). Growing season CO<sub>2</sub> fluxes from a drained peatland dominated by <i>Molinia caerulea</i>.
MIRES AND PEAT,
24 Author URL.
Carless D, Luscombe DJ, Gatis N, Anderson K, Brazier RE (2019). Mapping landscape-scale peatland degradation using airborne lidar and multispectral data. Landscape Ecology, 34, 1329-1345.
Ritson JP, Croft JK, Clark JM, Brazier RE, Templeton MR, Smith D, Graham NJD (2019). Sources of dissolved organic carbon (DOC) in a mixed land use catchment (Exe, UK).
Science of the Total Environment,
666, 165-175.
Abstract:
Sources of dissolved organic carbon (DOC) in a mixed land use catchment (Exe, UK)
Many catchment management schemes in the UK have focussed on peatland restoration to improve ecosystem services such as carbon sequestration, water quality and biodiversity. The effect of these schemes on dissolved organic carbon (DOC) flux is critical in understanding peatland carbon budgets as well as the implications for drinking water treatment. In many catchments, however, peatland areas are not the only source of DOC, meaning that their significance at the full catchment scale is unclear. In this paper we have evaluated the importance of different land uses as sources of DOC by combining three datasets obtained from the Exe catchment, UK. The first dataset comprises a weekly monitoring record at three sites for six years, the second, a monthly monitoring record of 25 sites in the same catchment for one year, and the third, an assessment of DOC export from litter and soil carbon stocks. Our results suggest that DOC concentration significantly increased from the peaty headwaters to the mixed land-use areas (ANOVA F = 12.52, p < 0.001, df = 2), leading to higher flux estimates at the downstream sites. We present evidence for three possible explanations: firstly, that poor sampling of high flows may lead to underestimation of DOC flux, second, that there are significant sources of DOC besides the peatland headwaters, and finally, that biological- and photo-degradation decreases the influence of upstream DOC sources. Our results provide evidence both for the targeting of catchment management in peatland areas as well as the need to consider DOC from agricultural and forested areas of the catchment.
Abstract.
Forsmoo J, Anderson K, Macleod CJA, Wilkinson ME, DeBell L, Brazier RE (2019). Structure from motion photogrammetry in ecology: Does the choice of software matter?.
Ecology and Evolution,
9(23), 12964-12979.
Abstract:
Structure from motion photogrammetry in ecology: Does the choice of software matter?
AbstractImage‐based modeling, and more precisely, Structure from Motion (SfM) and Multi‐View Stereo (MVS), is emerging as a flexible, self‐service, remote sensing tool for generating fine‐grained digital surface models (DSMs) in the Earth sciences and ecology. However, drone‐based SfM + MVS applications have developed at a rapid pace over the past decade and there are now many software options available for data processing. Consequently, understanding of reproducibility issues caused by variations in software choice and their influence on data quality is relatively poorly understood. This understanding is crucial for the development of SfM + MVS if it is to fulfill a role as a new quantitative remote sensing tool to inform management frameworks and species conservation schemes. To address this knowledge gap, a lightweight multirotor drone carrying a Ricoh GR II consumer‐grade camera was used to capture replicate, centimeter‐resolution image datasets of a temperate, intensively managed grassland ecosystem. These data allowed the exploration of method reproducibility and the impact of SfM + MVS software choice on derived vegetation canopy height measurement accuracy. The quality of DSM height measurements derived from four different, yet widely used SfM‐MVS software—Photoscan, Pix4D, 3DFlow Zephyr, and MICMAC, was compared with in situ data captured on the same day as image capture. We used both traditional agronomic techniques for measuring sward height, and a high accuracy and precision differential GPS survey to generate independent measurements of the underlying ground surface elevation. Using the same replicate image dataset (n = 3) as input, we demonstrate that there are 1.7, 2.0, and 2.5 cm differences in RMSE (excluding one outlier) between the outputs from different SfM + MVS software using High, Medium, and Low quality settings, respectively. Furthermore, we show that there can be a significant difference, although of small overall magnitude between replicate image datasets (n = 3) processed using the same SfM + MVS software, following the same workflow, with a variance in RMSE of up to 1.3, 1.5, and 2.7 cm (excluding one outlier) for “High,” “Medium,” and “Low” quality settings, respectively. We conclude that SfM + MVS software choice does matter, although the differences between products processed using “High” and “Medium” quality settings are of small overall magnitude.
Abstract.
Auster R, Puttock A, Brazier R (2019). Unravelling perceptions of Eurasian beaver reintroduction in Great Britain. AREA
2018
Brazier RE, humphries RN (2018). Exploring the case for a national-scale soil conservation and soil condition 1 framework for evaluating and reporting on environmental and land use 2 policies. Soil Use and Management
Ashe J, Grand-Clement E, Smith D, Brazier RE, Savic DA (2018). Extracting Value from Complex High-Frequency Multivariate Water Quality Data: Exploring Routinely Collected Operational Data.
Gatis N, Luscombe D, Carless D, Parry L, Fyfe R, Harrod T, Brazier RE, Anderson K (2018). Mapping upland peat depth using airborne radiometric and lidar survey data.
Geoderma,
335, 78-89.
Abstract:
Mapping upland peat depth using airborne radiometric and lidar survey data
A method to estimate peat depth and extent is vital for accurate estimation of carbon stocks and to facilitate appropriate peatland management. Current methods for direct measurement (e.g. ground penetrating radar, probing) are labour intensive making them unfeasible for capturing spatial information at landscape extents. Attempts to model peat depths using remotely sensed data such as elevation and slope have shown promise but assume a functional relationship between current conditions and gradually accrued peat depth. Herein we combine LiDAR-derived metrics known to influence peat accumulation (elevation, slope, topographic wetness index (TWI)) with passive gamma-ray spectrometric survey data, shown to correlate with peat occurrence to develop a novel peat depth model for Dartmoor.
Total air absorbed dose rates of Thorium, Uranium and Potassium were calculated, referred to as radiometric dose. Relationships between peat depth, radiometric dose, elevation, slope and TWI were trained using 1334 peat depth measurements, a further 445 measurements were used for testing. All variables showed significant relationships with peat depth. Linear stepwise regression of natural log-transformed variables indicated that a radiometric dose and slope model had an r2 = 0.72/0.73 and RMSE 0.31/0.31 m for training/testing respectively. This model estimated an area of 158 ±101 km2 of peaty soil >0.4 m deep across the study area. Much of this area (60 km2) is overlain by grassland and therefore may have been missed if vegetation cover was used to map peat extent. Using published bulk density and carbon content values we estimated 13.1 Mt C (8.1-21.9 Mt C) are stored in the peaty soils within the study area. This is an increase on previous estimates due to greater modelled peat depth. The combined use of airborne gamma-ray spectrometric survey and LiDAR data provide a novel, practical and repeatable means to estimate peat depth with no a priori knowledge, at an appropriate resolution (10 m) and extent (406 km2) to facilitate management of entire peatland complexes.
Abstract.
Brown AG, Lespez L, Sear DA, Macaire JJ, Houben P, Klimek K, Brazier RE, Van Oost K, Pears B (2018). Natural vs anthropogenic streams in Europe: History, ecology and implications for restoration, river-rewilding and riverine ecosystem services.
Earth-Science Reviews,
180, 185-205.
Abstract:
Natural vs anthropogenic streams in Europe: History, ecology and implications for restoration, river-rewilding and riverine ecosystem services
In Europe and North America the prevailing model of “natural” lowland streams is incised-meandering channels with silt-clay floodplains, and this is the typical template for stream restoration. Using both published and new unpublished geological and historical data from Europe we critically review this model, show how it is inappropriate for the European context, and examine the implications for carbon sequestration and Riverine Ecosystem Services (RES) including river rewilding. This paper brings together for the first time, all the pertinent strands of evidence we now have on the long-term trajectories of floodplain system from sediment-based dating to sedaDNA. Floodplain chronostratigraphy shows that early Holocene streams were predominantly multi-channel (anabranching) systems, often choked with vegetation and relatively rarely single-channel actively meandering systems. Floodplains were either non-existent or limited to adjacent organic-filled palaeochannels, spring/valley mires and flushes. This applied to many, if not most, small to medium rivers but also major sections of the larger rivers such as the Thames, Seine, Rhône, Lower Rhine, Vistula and Danube. As shown by radiocarbon and optically stimulated luminescence (OSL) dating during the mid-late Holocene c. 4–2 ka BP, overbank silt-clay deposition transformed European floodplains, covering former wetlands and silting-up secondary channels. This was followed by direct intervention in the Medieval period incorporating weir and mill-based systems – part of a deep engagement with rivers and floodplains which is even reflected in river and floodplain settlement place names. The final transformation was the “industrialisation of channels” through hard-engineering – part of the Anthropocene great acceleration. The primary causative factor in transforming pristine floodplains was accelerated soil erosion caused by deforestation and arable farming, but with effective sediment delivery also reflecting climatic fluctuations. Later floodplain modifications built on these transformed floodplain topographies. So, unlike North America where channel-floodplain transformation was rapid, the transformation of European streams occurred over a much longer time-period with considerable spatial diversity regarding timing and kind of modification. This has had implications for the evolution of RES including reduced carbon sequestration over the past millennia. Due to the multi-faceted combination of catchment controls, ecological change and cultural legacy, it is impractical, if not impossible, to identify an originally natural condition and thus restore European rivers to their pre-transformation state (naturalisation). Nevertheless, attempts to restore to historical (pre-industrial) states allowing for natural floodplain processes can have both ecological and carbon offset benefits, as well as additional abiotic benefits such as flood attenuation and water quality improvements. This includes rewilding using beaver reintroduction which has overall positive benefits on river corridor ecology. New developments, particularly biomolecular methods offer the potential of unifying modern ecological monitoring with the reconstruction of past ecosystems and their trajectories. The sustainable restoration of rivers and floodplains designed to maximise desirable RES and natural capital must be predicated on the awareness that Anthropocene rivers are still largely imprisoned in the banks of their history and this requires acceptance of an increased complexity for the achievement and maintenance of desirable restoration goals.
Abstract.
Puttock A, Brazier R, Graham H, Carless D (2018). Sediment and nutrient storage in a beaver engineered wetland. Earth Surface Processes and Landforms
Bell MC, Ritson JP, Verhoef A, Brazier RE, Templeton MR, Graham NJD, Freeman C, Clark JM (2018). Sensitivity of peatland litter decomposition to changes in temperature and rainfall.
Geoderma,
331, 29-37.
Abstract:
Sensitivity of peatland litter decomposition to changes in temperature and rainfall
Changes to climate are projected over the next 50 years for many peatland areas. As decomposition of peat-forming vegetation is likely to be intrinsically linked to these changes in climate, a clear understanding of climate-peat dynamics is required. There is concern that increased temperature and decreased precipitation could increase the rate of decomposition and put the carbon sink status of many peatlands at risk, yet few studies have examined the impact of both climatic factors together. To better understand the sensitivity of peatland decomposition to changes in both temperature and precipitation and their interaction, we conducted a short-term laboratory experiment in which plant litters and peat soil were incubated, in isolation, in a factorial design. Treatments simulated baseline and projected climate averages derived from the latest UK climate change projections (UKCP09) for Exmoor, a climatically marginal peatland in SW England. Regular carbon dioxide flux measurements were made throughout the simulation, as well as total mass loss and total dissolved organic carbon (DOC) leached. The largest effect on carbon loss in this multifactor experiment was from substrate, with Sphagnum/peat releasing significantly less C in total during the experiment than dwarf shrubs/graminoids. Climate effects were substrate specific, with the drier rainfall treatment increasing the DOC leaching from Calluna, but decreasing it from Sphagnum. Partitioning between CO2 and DOC was also affected by climate, but only for the peat and Sphagnum samples, where the future climate scenarios (warmer and drier) resulted in a greater proportion of C lost in gaseous form. These results suggest that indirect effects of climate through changes in species composition in peatlands could ultimately turn out to be more important for litter decomposition than direct effects of climate change from increased temperatures and decreased rainfall.
Abstract.
2017
Eludoyin AO, Griffith B, Orr RJ, Bol R, Quine TA, Brazier RE (2017). An evaluation of the hysteresis in chemical concentration–discharge (C–Q) relationships from drained, intensively managed grasslands in southwest England.
Hydrological Sciences Journal,
62(8), 1243-1254.
Abstract:
An evaluation of the hysteresis in chemical concentration–discharge (C–Q) relationships from drained, intensively managed grasslands in southwest England
This study examined the hysteresis exhibited in concentration–discharge (C–Q) relationships in the runoff from four hydrologically separated fields (catchments) at an intensively managed grassland. The objectives were to examine C–Q relationships constructed from high-resolution time series of flow, temperature, pH, conductivity, nitrate and turbidity, and their implications for hydrological processes. High-resolution datasets from the quality assured records of the Rothamsted Research North Wyke Farm Platform in the UK were examined using a graphical method and cross-correlation statistics. The study found that storm events based C–Q hysteresis reflects the cross-correlation that is generally hidden in time series analysis of large datasets, and that although Q and water quality variables can be effectively influenced by catchment size, the C–Q relationship is less significantly influenced. The dominant C–Q relationships of the water variables in the study area reflect that saturated overland flow was prevalent during the study period in the catchments, while the CCF results indicate coupled transfer of sediments and solute in the area at lag ≥ 0. EDITOR D. Koutsoyiannis ASSOCIATE EDITOR M. D. Fidelibus.
Abstract.
Turley MD, Bilotta GS, Arbociute G, Chadd RP, Extence CA, Brazier RE (2017). Quantifying Submerged Deposited Fine Sediments in Rivers and Streams Using Digital Image Analysis.
River Research and Applications,
33(10), 1585-1595.
Abstract:
Quantifying Submerged Deposited Fine Sediments in Rivers and Streams Using Digital Image Analysis
Deposited fine sediment is an essential component of freshwater ecosystems. Nonetheless, anthropogenic activities can modify natural fine sediment levels, impacting the physical, chemical and biological characteristics of these ecosystems. An ability to quantify deposited fine sediment is critical to understanding its impacts and successfully managing the anthropogenic activities that are responsible for modifying it. One widely used method, the visual estimate technique, relies on subjective estimates of particle size and percentage cover. In this paper, we present two novel alternative approaches, based on non-automated digital image analysis (DIA), which are designed to reduce the subjectivity of submerged and surficial fine sediment estimates, and provide a verifiable record of the conditions at the time of sampling. The DIA methods were tested across five systematically selected, contrasting temperate stream and river typologies, over three seasons of monitoring. The resultant sediment metrics were strongly, positively correlated with visual estimates (rs = 0.90, and rs = 0.82, p < 0.01), and similarly strongly, but negatively correlated with a sediment-specific biotic index, suggesting some degree of biological relevance. The DIA technique has the potential to be a valuable tool for application in numerous areas of river research, where a non-destructive, less subjective and verifiable method is desirable. Copyright ©2016 the Authors River Research and Applications Published by John Wiley & Sons Ltd.
Abstract.
Ritson JP, Brazier RE, Graham NJD, Freeman C, Templeton MR, Clark JM (2017). The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources.
Biogeosciences,
14(11), 2891-2902.
Abstract:
The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources
Drought conditions are expected to increase in frequency and severity as the climate changes, representing a threat to carbon sequestered in peat soils. Downstream water treatment works are also at risk of regulatory compliance failures and higher treatment costs due to the increase in riverine dissolved organic carbon (DOC) often observed after droughts. More frequent droughts may also shift dominant vegetation in peatlands from Sphagnum moss to more drought-tolerant species. This paper examines the impact of drought on the production and treatability of DOC from four vegetation litters (Calluna vulgaris, Juncus effusus, Molinia caerulea and Sphagnum spp.) and a peat soil. We found that mild droughts caused a 39.6% increase in DOC production from peat and that peat DOC that had been exposed to oxygen was harder to remove by conventional water treatment processes (coagulation/flocculation). Drought had no effect on the amount of DOC production from vegetation litters; however large variation was observed between typical peatland species (Sphagnum and Calluna) and drought-tolerant grassland species (Juncus and Molinia), with the latter producing more DOC per unit weight. This would therefore suggest the increase in riverine DOC often observed post-drought is due entirely to soil microbial processes and DOC solubility rather than litter layer effects. Long-term shifts in species diversity may, therefore, be the most important impact of drought on litter layer DOC flux, whereas pulses related to drought may be observed in peat soils and are likely to become more common in the future. These results provide evidence in support of catchment management which increases the resilience of peat soils to drought, such as ditch blocking to raise water tables.
Abstract.
Ritson JP, Brazier RE, Graham NJD, Freeman C, Templeton MR, Clark JM (2017). The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources. , 1-20.
2016
Turley MD, Bilotta GS, Chadd RP, Extence CA, Brazier RE, Burnside NG, Pickwell AGG (2016). A sediment-specific family-level biomonitoring tool to identify the impacts of fine sediment in temperate rivers and streams.
Ecological Indicators,
70, 151-165.
Abstract:
A sediment-specific family-level biomonitoring tool to identify the impacts of fine sediment in temperate rivers and streams
Anthropogenic modifications of sediment load can cause ecological degradation in stream and river ecosystems. However, in practice, identifying when and where sediment is the primary cause of ecological degradation is a challenging task. Biological communities undergo natural cycles and variation over time, and respond to a range of physical, chemical and biological pressures. Furthermore, fine sediments are commonly associated with numerous other pressures that are likely to influence aquatic biota. The use of conventional, non-biological monitoring to attribute cause and effect would necessitate measurement of multiple parameters, at sufficient temporal resolution, and for a significant period of time. Biomonitoring tools, which use low-frequency measurements of biota to gauge and track changes in the environment, can provide a valuable alternative means to detecting the effects of a given pressure. In this study, we develop and test an improved macroinvertebrate, family-level and mixed-level biomonitoring tool for fine sediment. Biologically-based classifications of sediment sensitivity were supplemented by using empirical data of macroinvertebrate abundance and percentage fine sediment, collected across a wide range of temperate river and stream ecosystems (model training dataset n = 2252) to assign detailed individual sensitivity weights to taxa. An optimum set of weights were identified by non-linear optimisation, as those that resulted in the highest Spearman's rank correlation coefficient between the index (called the Empirically-weighted Proportion of Sediment-sensitive Invertebrates index; E-PSI) scores and deposited fine sediment in the model training dataset. The family and mixed-level tools performed similarly, with correlations with percentage fine sediment in the test dataset (n = 84) of rs = -0.72 and rs = -0.70 p < 0.01. Testing of the best performing family level version, over agriculturally impacted sites (n = 754) showed similar correlations to fine sediment (rs = -0.68 p < 0.01). The tools developed in this study have retained their biological basis, are easily integrated into contemporary monitoring agency protocols and can be applied retrospectively to historic datasets. Given the challenges of non-biological conventional monitoring of fine sediments and determining the biological relevance of the resulting data, a sediment-specific biomonitoring approach is highly desirable and will be a useful addition to the suite of pressure-specific biomonitoring tools currently used to infer the causes of ecological degradation.
Abstract.
Harris P, Howden NJK, Peukert S, Noacco V, Ramezani K, Tuominen E, Eludoyin B, Brazier R, Shepherd A, Griffith B, et al (2016). Contextualized Geographically Weighted Principal Components Analysis for Investigating Baseline Soils Data on the North Wyke Farm Platform. In (Ed) Geostatistical and Geospatial Approaches for the Characterization of Natural Resources in the Environment, Springer Nature, 651-655.
Cunliffe AM, Puttock AK, Turnbull L, Wainwright J, Brazier RE (2016). Dryland, calcareous soils store (and lose) significant quantities of near-surface organic carbon.
Journal of Geophysical Research: Earth Surface,
121(4), 684-702.
Abstract:
Dryland, calcareous soils store (and lose) significant quantities of near-surface organic carbon
©2016. The Authors. Semiarid ecosystems are susceptible to changes in dominant vegetation which may have significant implications for terrestrial carbon dynamics. The present study examines the distribution of organic carbon (OC) between particle size fractions in near-surface (0-0.05 m) soil and the water erosion-induced redistribution of particle-associated OC over a grass-shrub ecotone, in a semiarid landscape, subject to land degradation. Coarse ( > 2 mm) particles have comparable average OC concentrations to the fine ( < 2 mm) particles, accounting for ~24-38% of the OC stock in the near-surface soil. This may be due to aggregate stabilization by precipitated calcium carbonate in these calcareous arid soils. Critically, standard protocols assuming that coarse fraction particles contain no OC are likely to underestimate soil OC stocks substantially, especially in soils with strongly stabilized aggregates. Sediment eroded from four hillslope scale (10 × 30 m) sites during rainstorm events was monitored over four annual monsoon seasons. Eroded sediment was significantly enriched in OC; enrichment increased significantly across the grass-shrub ecotone and appears to be an enduring phenomenon probably sustained through the dynamic replacement of preferentially removed organic matter. The average erosion-induced OC event yield increased sixfold across th e ecotone from grass-dominated to shrub-dominated ecosystems, due to both greater erosion and greater OC enrichment. This erosional pathway is rarely considered when comparing the carbon budgets of grasslands and shrublands, yet this accelerated efflux of OC may be important for long-term carbon storage potentials of dryland ecosystems.
Abstract.
Puttock A, Graham HA, Cunliffe AM, Elliott M, Brazier RE (2016). Eurasian beaver activity increases water storage, attenuates flow and mitigates diffuse pollution from intensively-managed grasslands.
Science of the Total Environment,
576, 430-443.
Abstract:
Eurasian beaver activity increases water storage, attenuates flow and mitigates diffuse pollution from intensively-managed grasslands
© 2016 the Authors Beavers are the archetypal keystone species, which can profoundly alter ecosystem structure and function through their ecosystem engineering activity, most notably the building of dams. This can have a major impact upon water resource management, flow regimes and water quality. Previous research has predominantly focused on the activities of North American beaver (Castor canadensis) located in very different environments, to the intensive lowland agricultural landscapes of the United Kingdom and elsewhere in Europe. Two Eurasian beavers (Castor fiber) were introduced to a wooded site, situated on a first order tributary, draining from intensively managed grassland. The site was monitored to understand impacts upon water storage, flow regimes and water quality. Results indicated that beaver activity, primarily via the creation of 13 dams, has increased water storage within the site (holding ca. 1000 m 3 in beaver ponds) and beavers were likely to have had a significant flow attenuation impact, as determined from peak discharges (mean 30 ± 19% reduction), total discharges (mean 34 ± 9% reduction) and peak rainfall to peak discharge lag times (mean 29 ± 21% increase) during storm events. Event monitoring of water entering and leaving the site showed lower concentrations of suspended sediment, nitrogen and phosphate leaving the site (e.g. for suspended sediment; average entering site: 112 ± 72 mg l − 1 , average leaving site: 39 ± 37 mg l − 1 ). Combined with attenuated flows, this resulted in lower diffuse pollutant loads in water downstream. Conversely, dissolved organic carbon concentrations and loads downstream were higher. These observed changes are argued to be directly attributable to beaver activity at the site which has created a diverse wetland environment, reducing downstream hydrological connectivity. Results have important implications for beaver reintroduction programs which may provide nature based solutions to the catchment-scale water resource management issues that are faced in agricultural landscapes.
Abstract.
Luscombe DJ, Anderson K, Grand-Clement E, Gatis N, Ashe J, Benaud P, Smith D, Brazier RE (2016). How does drainage alter the hydrology of shallow degraded peatlands across multiple spatial scales?.
Journal of Hydrology,
541, 1329-1339.
Abstract:
How does drainage alter the hydrology of shallow degraded peatlands across multiple spatial scales?
Shallow, degraded peatlands differ in both their structure and function from deeper, peatland ecosystems. Previous work has shown that shallow, drained peatlands demonstrate rapid storm runoff that is only minimally controlled by antecedent hydrological conditions. However, such peatlands are also known to exhibit significant variation in ecohydrological organisation and structure across different spatial scales. In addition, predictions of hydrological response using spatially distributed numerical models of rainfall-runoff may be flawed unless they are evaluated with datasets describing the spatial variability of hydrological responses. This paper evaluates to what extent, flow generation and water storage within shallow, degraded peatland catchments may be controlled by the spatial attributes of the contributing area of the peatland, the drainage ditch size, morphology and geometry. Results from an experiment conducted over multiple spatial scales and multi-annual timescales highlights that subtle variations in the local slope and topography account for the long-term spatial patterns of water table depth. Neither the local scale of the drainage feature or the topographic contributing area is shown to be a definitive predictor of runoff in the studied catchments. Results also highlight the importance of using spatially distributed observations to ensure that estimates of water storage and runoff are representative of the fine scale spatial variability that occurs in such damaged and shallow peatlands.
Abstract.
Ritson JP, Bell M, Brazier RE, Grand-Clement E, Graham NJD, Freeman C, Smith D, Templeton MR, Clark JM (2016). Managing peatland vegetation for drinking water treatment.
Sci Rep,
6Abstract:
Managing peatland vegetation for drinking water treatment.
Peatland ecosystem services include drinking water provision, flood mitigation, habitat provision and carbon sequestration. Dissolved organic carbon (DOC) removal is a key treatment process for the supply of potable water downstream from peat-dominated catchments. A transition from peat-forming Sphagnum moss to vascular plants has been observed in peatlands degraded by (a) land management, (b) atmospheric deposition and (c) climate change. Here within we show that the presence of vascular plants with higher annual above-ground biomass production leads to a seasonal addition of labile plant material into the peatland ecosystem as litter recalcitrance is lower. The net effect will be a smaller litter carbon pool due to higher rates of decomposition, and a greater seasonal pattern of DOC flux. Conventional water treatment involving coagulation-flocculation-sedimentation may be impeded by vascular plant-derived DOC. It has been shown that vascular plant-derived DOC is more difficult to remove via these methods than DOC derived from Sphagnum, whilst also being less susceptible to microbial mineralisation before reaching the treatment works. These results provide evidence that practices aimed at re-establishing Sphagnum moss on degraded peatlands could reduce costs and improve efficacy at water treatment works, offering an alternative to 'end-of-pipe' solutions through management of ecosystem service provision.
Abstract.
Author URL.
Peukert S, Griffith BA, Murray PJ, Macleod CJA, Brazier RE (2016). Spatial variation in soil properties and diffuse losses between and within grassland fields with similar short-term management.
European Journal of Soil Science,
67(4), 386-396.
Abstract:
Spatial variation in soil properties and diffuse losses between and within grassland fields with similar short-term management
One of the major challenges for agriculture is to understand the effects of agricultural practices on soil properties and diffuse pollution, to support practical farm-scale land management. Three conventionally managed grassland fields with similar short-term management, but different ploughing histories, were studied on a long-term research platform: the North Wyke Farm Platform. The aims were to (i) quantify the between-field and within-field spatial variation in soil properties by geostatistical analysis, (ii) understand the effects of soil condition (in terms of nitrogen, phosphorus and carbon contents) on the quality of discharge water and (iii) establish robust baseline data before the implementation of various grassland management scenarios. Although the fields sampled had experienced the same land use and similar management for at least 6 years, there were differences in their mean soil properties. They showed different patterns of soil spatial variation and different rates of diffuse nutrient losses to water. The oldest permanent pasture field had the largest soil macronutrient concentrations and the greatest diffuse nutrient losses. We show that management histories affect soil properties and diffuse losses. Potential gains in herbage yield or benefits in water quality might be achieved by characterizing every field or by area-specific management within fields (a form of precision agriculture for grasslands). Permanent pasture per se cannot be considered a mitigation measure for diffuse pollution. The between- and within-field soil spatial variation emphasizes the importance of baseline characterization and will enable the reliable identification of any effects of future management change on the Farm Platform. Highlights: Quantification of soil and water quality in grassland fields with contrasting management histories. Considerable spatial variation in soil properties and diffuse losses between and within fields. Contrasting management histories within and between fields strongly affected soil and water quality. Careful pasture management needed: the oldest pasture transferred the most nutrients from soil to water.
Abstract.
Cunliffe A, Brazier RE, Anderson K (2016). Ultra-fine grain landscape-scale quantification of dryland vegetation structure with drone-acquired structure-from-motion photogrammetry.
Remote Sensing of Environment,
183, 129-143.
Abstract:
Ultra-fine grain landscape-scale quantification of dryland vegetation structure with drone-acquired structure-from-motion photogrammetry
Covering 40% of the terrestrial surface, dryland ecosystems characteristically have distinct vegetation structures that are strongly linked to their function. Existing survey approaches cannot provide sufficiently fine-resolution data at landscape-level extents to quantify this structure appropriately. Using a small, unpiloted aerial system (UAS) to acquire aerial photographs and processing theses using structure-from-motion (SfM) photogrammetry, three-dimensional models were produced describing the vegetation structure of semi-arid ecosystems at seven sites across a grass–to shrub transition zone. This approach yielded ultra-fine (< 1 cm2) spatial resolution canopy height models over landscape-levels (10 ha), which resolved individual grass tussocks just a few cm3 in volume. Canopy height cumulative distributions for each site illustrated ecologically-significant differences in ecosystem structure. Strong coefficients of determination (r2 from 0.64 to 0.95) supported prediction of above-ground biomass from canopy volume. Canopy volumes, above-ground biomass and carbon stocks were shown to be sensitive to spatial changes in the structure of vegetation communities. The grain of data produced and sensitivity of this approach is invaluable to capture even subtle differences in the structure (and therefore function) of these heterogeneous ecosystems subject to rapid environmental change. The results demonstrate how products from inexpensive UAS coupled with SfM photogrammetry can produce ultra-fine grain biophysical data products, which have the potential to revolutionise scientific understanding of ecology in ecosystems with either spatially or temporally discontinuous canopy cover.
Abstract.
2015
Puttock A, Cunliffe AM, Anderson K, Brazier RE (2015). Aerial photography collected with a multirotor drone reveals impact of Eurasian beaver reintroduction on ecosystem structure.
Journal of Unmanned Vehicle Systems Author URL.
Turley MD, Bilotta GS, Krueger T, Brazier RE, Extence CA (2015). Developing an improved biomonitoring tool for fine sediment: Combining expert knowledge and empirical data.
Ecological Indicators,
54, 82-86.
Abstract:
Developing an improved biomonitoring tool for fine sediment: Combining expert knowledge and empirical data
The Proportion of Sediment-sensitive Invertebrates (PSI) index is a biomonitoring tool that is designed to identify the degree of sedimentation in rivers and streams. Despite having a sound biological basis, the tool has been shown to have only a moderate correlation with fine sediment, which although comparable to other pressure specific indices, limits confidence in its application. The aim of this study was to investigate if the performance of the PSI index could be enhanced through the use of empirical data to supplement the expert knowledge and literature which were used to determine the original four fine sediment sensitivity ratings. The empirical data used, comprised observations of invertebrate abundance and percentage fine sediment, collected across a wide range of reference condition temperate stream and river ecosystems (model training dataset n = 2252). Species were assigned sensitivity weights within a range based on their previously determined sensitivity rating. Using a range of weights acknowledges the breadth of ecological niches that invertebrates occupy and also their differing potential as indicators. The optimum species-specific sensitivity weights were identified using non-linear optimisation, as those that resulted in the highest Spearman's rank correlation coefficient between the Empirically-weighted PSI (E-PSI) scores and deposited fine sediment in the model training dataset. The correlation between percentage fine sediment and E-PSI scores in the test dataset (n = 252) was eight percentage points higher than the correlation between percentage fine sediment and the original PSI scores (E-PSI rs = -0.74, p < 0.01 compared to PSI rs = -0.66, p < 0.01). This study demonstrates the value of combining a sound biological basis with evidence from large empirical datasets, to test and enhance the performance of biomonitoring tools to increase confidence in their application.
Abstract.
Luscombe DJ, Anderson K, Gatis N, Grand-Clement E, Brazier RE (2015). Using airborne thermal imaging data to measure near-surface hydrology in upland ecosystems.
Hydrological Processes,
29(6), 1656-1668.
Abstract:
Using airborne thermal imaging data to measure near-surface hydrology in upland ecosystems
Upland ecosystems are recognized for their importance in providing valuable ecosystem services including water storage, water supply and flood attenuation alongside carbon storage and biodiversity. The UK contains 10-15% of the global resource of upland blanket peatlands, the hydrology and ecology of which are highly sensitive to external anthropogenic and climatic forcing. In particular, drainage of these landscapes for agricultural intensification and peat extraction has resulted in often unquantified damage to the peatland hydrology, and little is understood about the spatially distributed impacts of these practices on near-surface wetness. This paper develops new techniques to extract spatial data describing the near-surface wetness and hydrological behaviour of drained blanket peatlands using airborne thermal imaging data and airborne Light Detection and Ranging (LiDAR) data. The relative thermal emissivity (E{open}r) of the ground surface is mapped and used as a proxy for near-surface wetness. The results show how moorland drainage and land surface structure have an impact on airborne measurements of thermal emissivity. Specifically, we show that information on land surface structure derived from LiDAR can help normalize signals in thermal emissivity data to improve description of hydrological condition across a test catchment in Exmoor, UK. An in situ field hydrological survey was used to validate these findings. We discuss how such data could be used to describe the spatially distributed nature of near-surface water resources, to optimize catchment management schemes and to deliver improved understanding of the drivers of hydrological change in analogous ecosystems.
Abstract.
DeBell L, Anderson K, Brazier RE, Jones L, King N (2015). Water resource management at catchment scales using lightweight UAVs: current capabilities and future perspectives.
Journal of Unmanned Vehicle SystemsAbstract:
Water resource management at catchment scales using lightweight UAVs: current capabilities and future perspectives
Lightweight, portable unmanned aerial vehicles (UAVs) or ‘drones’ are set to become a key component of a water resource management (WRM) toolkit, but are currently not widely used in this context. In practical WRM there is a growing need for fine-scale responsive data, which cannot be delivered from satellites or aircraft in a cost-effective way. Such a capability is needed where water supplies are located in spatially heterogeneous dynamic catchments. In this review, we demonstrate the step change in hydrological process understanding that could be delivered if WRM employed UAVs. The paper discusses a range of pragmatic concepts in UAV science for cost-effective and practical WRM, from choosing the right sensor and platform combination through to practical deployment and data processing challenges. The paper highlights that multi-sensor approaches, such as combining thermal imaging with fine-scale structure-from-motion topographic models are currently best placed to assist WRM decisions because they provide a means of monitoring the spatio-temporal distribution of sources, sinks and flows of water through landscapes. The manuscript highlights areas where research is needed to support the integration of UAVs into practical WRM – e.g. in improving positional accuracy through integration of differential global positioning system sensors, and developing intelligent control of UAV platforms to optimize the accuracy of spatial data capture.
Abstract.
2014
Glendell M, Brazier RE (2014). Accelerated export of sediment and carbon from a landscape under intensive agriculture.
Sci Total Environ,
476-477, 643-656.
Abstract:
Accelerated export of sediment and carbon from a landscape under intensive agriculture.
The export of total organic carbon (particulate and dissolved) from terrestrial to aquatic ecosystems has important implications for water quality and the global carbon cycle. However, most research to date has focused on DOC losses from either forested or peaty catchments, with only limited studies examining the controls and rates of total fluvial carbon losses from agricultural catchments, particularly during storm events. This study examined the controls and fluxes of total suspended sediment (SS), total particulate (TPC) and dissolved organic carbon (DOC) from two adjacent catchments with contrasting intensive agricultural and semi-natural land-use. Data from 35 individual storm events showed that the agricultural catchment exported significantly higher SS concentrations on a storm-by-storm basis than the semi-natural catchment, with peak discharge exerting a greater control over SS, TPC and DOC concentrations. Baseflow DOC concentrations in the agricultural catchment were significantly higher. DOC quality monitored during one simultaneous rainfall event differed between the two study catchments, with more humic, higher molecular weight compounds prevailing in the agricultural catchment and lower molecular weight compounds prevailing in the semi-natural catchment. During an eight month period for which a comparable continuous turbidity record was available, the estimated SS yields from the agricultural catchment were higher than from the semi-natural catchment. Further, the agricultural catchment exported proportionally more TPC and a comparable amount of DOC, despite a lower total soil carbon pool. These results suggest that altered hydrological and biogeochemical processes within the agricultural catchment, including accelerated soil erosion and soil organic matter turnover, contributed to an enhanced fluvial SS and carbon export. Thus, we argue that enhancing semi-natural vegetation within intensively farmed catchments could reduce sediment and carbon losses from these areas and increase their resilience to more extreme hydrological events, anticipated as a result of climate change.
Abstract.
Author URL.
Brazier RE, Turnbull L, Wainwright J, Bol R (2014). Carbon loss by water erosion in drylands: Implications from a study of vegetation change in the south-west USA.
Hydrological Processes,
28(4), 2212-2222.
Abstract:
Carbon loss by water erosion in drylands: Implications from a study of vegetation change in the south-west USA
Soil organic carbon (SOC) is an important component of the global carbon cycle yet is rarely quantified adequately in terms of its spatial variability resulting from losses of SOC due to erosion by water. Furthermore, in drylands, little is known about the effect of widespread vegetation change on changes in SOC stores and the potential for water erosion to redistribute SOC around the landscape especially during high-magnitude run-off events (flash floods). This study assesses the change in SOC stores across a shrub-encroachment gradient in the Chihuahuan Desert of the south-west USA. A robust estimate of SOC storage in surface soils is presented, indicating that more SOC is stored beneath vegetation than in bare soil areas. In addition, the change in SOC storage over a shrub-encroachment gradient is shown to be nonlinear and highly variable within each vegetation type. Over the gradient of vegetation change, the heterogeneity of SOC increases, and newer carbon from C3 plants becomes dominant. This increase in the heterogeneity of SOC is related to an increase in water erosion and SOC loss from inter-shrub areas, which is self-reinforcing. Shrub-dominated drylands lose more than three times as much SOC as their grass counterparts. The implications of this study are twofold: (1) quantifying the effects of vegetation change on carbon loss via water erosion and the highly variable effects of land degradation on soil carbon stocks is critical. (2) If landscape-scale understanding of carbon loss by water erosion in drylands is required, studies must characterize the heterogeneity of ecosystem structure and its effects on ecosystem function across ecotones subject to vegetation change. © 2013 John Wiley & Sons, Ltd.
Abstract.
Harris P, Howden NJK, Peukert S, Noacco V, Ramezani K, Tuominen E, Eludoyin B, Brazier R, Shepherd A, Griffith B, et al (2014). Contextualized geographically weighted principal components analysis for investigating baseline soils data on the North Wyke Farm Platform.
Abstract:
Contextualized geographically weighted principal components analysis for investigating baseline soils data on the North Wyke Farm Platform
Abstract.
Turley MD, Bilotta GS, Extence CA, Brazier RE (2014). Evaluation of a fine sediment biomonitoring tool across a wide range of temperate rivers and streams.
Freshwater Biology,
59(11), 2268-2277.
Abstract:
Evaluation of a fine sediment biomonitoring tool across a wide range of temperate rivers and streams
Elevated levels of fine sediment (suspended and deposited) are a common cause of ecological degradation in freshwater ecosystems. However, it is time-consuming and expensive to monitor these parameters to support national and international water resource legislation. The Proportion of Sediment-sensitive Invertebrates (PSI) index is a biomonitoring tool that is designed to identify the degree of sedimentation in rivers and streams. Despite having a sound biological basis, until now, the PSI index has only been tested against observed fine sediment data in two catchments; other published applications of the PSI index have relied on inferred fine sediment values. In this study, we report the results of a comprehensive analysis of the performance of the PSI index across a wide range of reference condition temperate stream and river ecosystems, including 835 sites with data on deposited sediment and 451 sites with data on suspended solids (>12 500 data points measured between 1978 and 2002). The effect of taxonomic level and taxonomic resolution on the performance of the PSI index was also examined, as was the performance of the PSI index against other non-sediment-specific indices, including Average Score Per Taxon (ASPT), Lotic-invertebrate Index for Flow Evaluation (LIFE), Ephemeroptera, Plecoptera and Trichoptera (EPT) abundance, % EPT abundance, EPT richness and % EPT richness. The results of this study show that the PSI index was more correlated with fine sediment metrics than the other biological indices tested: rs = -0.64, (P < 0.01, n = 2502) for deposited sediment and rs = -0.50 (P < 0.01, n = 1353) for suspended solids. We highlight the optimal conditions for applying the PSI index, in its current form. Given the variability in the relationship between PSI and fine sediment metrics, we propose that the use of data from more objective, quantitative methods of measuring deposited fine sediment may help to enhance the performance of the model for future applications and advance understanding of fine sediment dynamics and the pressure-response relationship.
Abstract.
Liu S, Brazier RE, Heathwaite AL, Liu W (2014). Fully integrated approach: an alternative solution of coupling a GIS and diffuse pollution models.
FRONTIERS OF ENVIRONMENTAL SCIENCE & ENGINEERING,
8(4), 616-623.
Author URL.
Peukert S, Griffith BA, Murray PJ, Macleod CJA, Brazier RE (2014). Intensive management in grasslands causes diffuse water pollution at the farm scale.
Journal of Environmental Quality,
43(6), 2009-2023.
Abstract:
Intensive management in grasslands causes diffuse water pollution at the farm scale
Arable land use is generally assumed to be the largest contributor to agricultural diffuse pollution. This study adds to the growing evidence that conventional temperate intensively managed lowland grasslands contribute significantly to soil erosion and diffuse pollution rates. This is the first grassland study to monitor hydrological characteristics and multiple pollutant fluxes (suspended sediment [SS] and the macronutrients: total oxidized nitrogen-N [TONN], total phosphorus [TP], and total carbon [TC]) at high temporal resolution (monitoring up to every 15 min) over 1 yr. Monitoring was conducted across three fields (6.5-7.5 ha) on the North Wyke Farm Platform, UK. The estimated annual erosion rates (up to 527.4 kg ha-1), TP losses (up to 0.9 kg ha-1), and TC losses (up to 179 kg ha-1) were similar to or exceeded the losses reported for other grassland, mixed land-use, and arable sites. Annual yields of TONN (up to 3 kg ha-1) were less than arable land-use fluxes and earlier grassland N studies, an important result as the study site is situated within a Nitrate Vulnerable Zone. The high-resolution monitoring allowed detailed "system's functioning" understanding of hydrological processes, mobilization- transport pathways of individual pollutants, and the changes of the relative importance of diffuse pollutants through flow conditions and time. Suspended sediment and TP concentrations frequently exceeded water quality guidelines recommended by the European Freshwater Fisheries Directive (25 mg L-1) and the European Water Framework Directive (0.04 mg soluble reactive P L-1), suggesting that intensively managed grasslands pose a significant threat to receiving surface waters. Such sediment and nutrient losses from intensively managed grasslands should be acknowledged in land management guidelines and advice for future compliance with surface water quality standards.
Abstract.
Glendell M, Granger SJ, Bol R, Brazier RE (2014). Quantifying the spatial variability of soil physical and chemical properties in relation to mitigation of diffuse water pollution.
Geoderma,
214-215, 25-41.
Abstract:
Quantifying the spatial variability of soil physical and chemical properties in relation to mitigation of diffuse water pollution
Understanding spatial variability of soil properties in response to land-use impacts is essential for evaluating the effectiveness of measures taken to address diffuse water pollution from agriculture. However, despite the growing emphasis on integrated catchment-scale implementation of land-use mitigation measures, the baseline landscape-scale evaluation of the spatial variability of key soil nutrients remains scarce. This study employs a high resolution geostatistical approach to characterise the spatial variability of parameters, including soil bulk density (BD), total soil carbon (TC), nitrogen (TN), phosphorus (TP), inorganic phosphorus (IP), organic phosphorus (OP), stable nitrogen isotope ratio (δ15N), C:N ratio, carbon storage and nitrogen storage in two study catchments with contrasting land uses (agricultural and semi-natural) that are subject to targeted management interventions to reduce flood risk and improve water quality. We found a stronger degree of spatial dependence of all soil properties in the agricultural than the semi-natural catchment, except for bulk density and δ15N. Furthermore, bulk density, TP, IP, OP, C:N ratio, δ15N and carbon storage showed a longer range or spatial auto-correlation in the agricultural catchment. The central tendency (median and mean) of all soil properties was also significantly different between the two catchments, with the exception of IP and δ15N. The spatial correlations between the soil properties pointed to the mechanisms that were responsible for the observed differences, whilst the krigged surfaces of soil variables identified most likely critical source areas for targeted land management interventions to improve water quality. Arable and intensive grasslands were identified as 'high-impact' land uses, associated with negative alteration of soil properties and increased diffuse water pollution, whilst moorland was a 'low impact' land use associated with improved water quality. A comparison with the national soil survey dataset shows that whilst it can be relied upon for the broad characterisation of carbon and TP stocks in the two study catchments, it underestimates the spatial variability of key soil properties in certain soil types and land uses. As the restoration of soil spatial heterogeneity may take several decades, a high resolution geostatistical approach should be included in the future design of catchment-scale monitoring schemes to inform catchment management strategies and elucidate the time frame over which landscape scale improvements in soil properties and corresponding ecosystem services can be achieved. © 2013 Elsevier B.V.
Abstract.
Ritson JP, Bell M, Graham NJD, Templeton MR, Brazier RE, Verhoef A, Freeman C, Clark JM (2014). Simulated climate change impact on summer dissolved organic carbon release from peat and surface vegetation: implications for drinking water treatment.
Water Res,
67, 66-76.
Abstract:
Simulated climate change impact on summer dissolved organic carbon release from peat and surface vegetation: implications for drinking water treatment.
Uncertainty regarding changes in dissolved organic carbon (DOC) quantity and quality has created interest in managing peatlands for their ecosystem services such as drinking water provision. The evidence base for such interventions is, however, sometimes contradictory. We performed a laboratory climate manipulation using a factorial design on two dominant peatland vegetation types (Calluna vulgaris and Sphagnum Spp.) and a peat soil collected from a drinking water catchment in Exmoor National Park, UK. Temperature and rainfall were set to represent baseline and future conditions under the UKCP09 2080s high emissions scenario for July and August. DOC leachate then underwent standard water treatment of coagulation/flocculation before chlorination. C. vulgaris leached more DOC than Sphagnum Spp. (7.17 versus 3.00 mg g(-1)) with higher specific ultraviolet (SUVA) values and a greater sensitivity to climate, leaching more DOC under simulated future conditions. The peat soil leached less DOC (0.37 mg g(-1)) than the vegetation and was less sensitive to climate. Differences in coagulation removal efficiency between the DOC sources appears to be driven by relative solubilisation of protein-like DOC, observed through the fluorescence peak C/T. Post-coagulation only differences between vegetation types were detected for the regulated disinfection by-products (DBPs), suggesting climate change influence at this scale can be removed via coagulation. Our results suggest current biodiversity restoration programmes to encourage Sphagnum Spp. will result in lower DOC concentrations and SUVA values, particularly with warmer and drier summers.
Abstract.
Author URL.
Hutton C, Nicholas A, Brazier R (2014). Sub-grid scale parameterization of hillslope runoff and erosion processes for catchment-scale models of semi-arid landscapes.
Hydrological Processes,
28(4), 1713-1721.
Abstract:
Sub-grid scale parameterization of hillslope runoff and erosion processes for catchment-scale models of semi-arid landscapes
The processes of hillslope runoff and erosion are typically represented at coarse spatial resolution in catchment-scale models due to computational limitations. Such representation typically fails to incorporate the important effects of topographic heterogeneity on runoff generation, overland flow, and soil erosion. These limitations currently undermine the application of distributed catchment models to understand the importance of thresholds and connectivity on hillslope and catchment-scale runoff and erosion, particularly in semi-arid environments. This paper presents a method for incorporating high-resolution topographic data to improve sub-grid scale parameterization of hillslope overland flow and erosion models. Results derived from simulations conducted using a kinematic wave overland flow model at 0.5m spatial resolution are used to parameterize the depth-discharge relationship in the overland flow model when applied at 16m resolution. The high-resolution simulations are also used to derive a more realistic parameterization of excess flow shear stress for use in the 16m resolution erosion model. Incorporating the sub-grid scale parameterization in the coarse-resolution model (16m) leads to improved predictions of overland flow and erosion when evaluated using results derived from high-resolution (0.5m) model simulations. The improvement in performance is observed for a range of event magnitudes and is most notable for erosion estimates due to the non-linear dependency between the rates of erosion and overland flow. © 2013 John Wiley & Sons, Ltd.
Abstract.
Glendell M, Extence C, Chadd R, Brazier RE (2014). Testing the pressure-specific invertebrate index (PSI) as a tool for determining ecologically relevant targets for reducing sedimentation in streams.
Freshwater Biology,
59(2), 353-367.
Abstract:
Testing the pressure-specific invertebrate index (PSI) as a tool for determining ecologically relevant targets for reducing sedimentation in streams
Sedimentation is a major cause of river impairment and water pollution worldwide. However, setting an ecologically meaningful sedimentation target is proving challenging due to significant gaps in the understanding of quantitative links between sedimentation and ecological response as well as variability between different types of surface waters. This study evaluates the utility of a new pressure-specific macroinvertebrate index, Proportion of Sediment-sensitive Invertebrates (PSI), to act as a simple tool for measuring sedimentation impacts and setting ecologically relevant sedimentation targets. Five macroinvertebrate indices were calculated from 51 samples taken from 13 sampling locations across two neighbouring, but contrasting study catchments in spring and autumn 2010 and 2011. For four of these, environmental quality indices (EQIs) were also calculated as a proportion of observed to expected (O:E) macroinvertebrate scores, which were predicted for a theoretical pristine invertebrate community using the River Invertebrate Prediction and Classification System model. Principal component analysis has shown a clear hydromorphological and sedimentation gradient within the two study catchments. A generalised hierarchical mixed model with site as a random factor and % fine bed sediment as a fixed factor found a significant relationship between PSI and O:E PSI and % fine bed sediment cover at reach-scale sampling resolution over a moderate gradient of impact. Lotic Index for Flow Evaluation (LIFE) scores and Ephemeroptera-Plecoptera-Trichoptera (EPT) % abundance were also related to % fine bed sediment cover. However, PSI was more strongly related to % fine bed sediment cover than either LIFE or EPT % abundance. While PSI and O:E PSI were correlated with LIFE and O:E LIFE, PSI was not correlated with EPT % abundance, which suggests a differentiated response of these metrics to multiple stressors. The relationship between PSI and other invertebrate metrics should be subjected to further testing along a pronounced gradient of multiple stressors, as our findings suggest that PSI and % fine bed sediment cover have the potential to provide simple, sensitive and effective tools for setting of 'twin' ecological and physical sedimentation targets and add additional exploratory power to the existing suite of macroinvertebrate indices. © 2013 John Wiley & Sons Ltd.
Abstract.
Hochstrasser T, Millington JA, Papanastasis V, Parsons A, Roggero P, Brazier R, Estrany J, Farina A, Puttock A (2014). The Study of Land Degradation in Drylands: State of the Art. In Mueller EN, Wainwright J, Parsons AJ, Turnbull L (Eds.)
Patterns of Land Degradation in Drylands, Springer Netherlands, 13-54.
Author URL.
Luscombe DJ, Anderson K, Gatis N, Wetherelt A, Grand-Clement E, Brazier RE (2014). What does airborne LiDAR really measure in upland ecosystems?.
EcohydrologyAbstract:
What does airborne LiDAR really measure in upland ecosystems?
Airborne laser scanning systems (Light Detection and Ranging, LiDAR) are very well suited to the study of landscape and vegetation structure over large extents. Spatially distributed measurements describing the three-dimensional character of landscape surfaces and vegetation architecture can be used to understand eco-geomorphic and ecohydrological processes, and this is particularly pertinent in peatlands given the increasing recognition that these landscapes provide a variety of ecosystem services (water provision, flood mitigation and carbon sequestration). In using LiDAR data for monitoring peatlands, it is important to understand how well peatland surface structures (with fine length scales) can be described. Our approach integrates two laser scanning technologies, namely terrestrial laser scanning (TLS) and airborne LiDAR surveys, to assess how effective airborne LiDAR is at measuring these fine-scale microtopographic ecohydrological structures. By combining airborne and TLS, we demonstrate an improved spatial understanding of the signal measured by the airborne LiDAR. Critically, results demonstrate that LiDAR digital surface models are subject to specific errors related to short-sward ecosystem structure, causing the vegetation canopy height and surface-drainage network depth to be underestimated. TLS is shown to be effective at describing these structures over small extents, allowing the information content and accuracy of airborne LiDAR to be understood and quantified more appropriately. These findings have important implications for the appropriate degree of confidence ecohydrologists can apply to such data when using them as a surrogate for field measurements. They also illustrate the need to couple LiDAR data with ground validation data in order to improve assessment of ecohydrological function in such landscapes. © 2014 John Wiley & Sons, Ltd.
Abstract.
Bol R, Puttock A, Dungait JAJ, Macleod CJA, Brazier RE (2014). Woody plant encroachment into grasslands leads to accelerated erosion of previously stable organic carbon from dryland soils.
Journal of Geophysical Research: Biogeosciences,
119(12), 2345-2357.
Abstract:
Woody plant encroachment into grasslands leads to accelerated erosion of previously stable organic carbon from dryland soils
Drylands worldwide are experiencing rapid and extensive environmental change, concomitant with the encroachment of woody vegetation into grasslands. Woody encroachment leads to changes in both the structure and function of dryland ecosystems and has been shown to result in accelerated soil erosion and loss of soil nutrients. Covering 40% of the terrestrial land surface, dryland environments are of global importance, both as a habitat and a soil carbon store. Relationships between environmental change, soil erosion, and the carbon cycle are uncertain. There is a clear need to further our understanding of dryland vegetation change and impacts on carbon dynamics. Here two grass-to-woody ecotones that occur across large areas of the southwestern United States are investigated. This study takes a multidisciplinary approach, combining ecohydrological monitoring of structure and function and a dual-proxy biogeochemical tracing approach using the unique natural biochemical signatures of the vegetation. Results show that following woody encroachment, not only do these drylands lose significantly more soil and organic carbon via erosion but that this includes significant amounts of legacy organic carbon which would previously have been stable under grass cover. Results suggest that these dryland soils may not act as a stable organic carbon pool, following encroachment and that accelerated erosion of carbon, driven by vegetation change, has important implications for carbon dynamics.
Abstract.
2013
Brazier RE, Turnbull L, Wainwright J, Bol R (2013). Carbon loss by water erosion in drylands: Implications from a study of vegetation change in the south-west USA. Hydrological Processes
Puttock A, Macleod CJA, Bol R, Sessford P, Dungait J, Brazier RE (2013). Changes in ecosystem structure, function and hydrological connectivity control water, soil and carbon losses in semi-arid grass to woody vegetation transitions.
Earth Surface Processes and Landforms,
38(13), 1602-1611.
Abstract:
Changes in ecosystem structure, function and hydrological connectivity control water, soil and carbon losses in semi-arid grass to woody vegetation transitions
Connectivity has recently emerged as a key concept for understanding hydrological response to vegetation change in semi-arid environments, providing an explanatory link between abiotic and biotic, structure and function. Reduced vegetation cover following woody encroachment, generally promotes longer, more connected overland flow pathways, which has the potential to result in an accentuated rainfall-runoff response and fluxes of both soil erosion and carbon. This paper investigates changing hydrological connectivity as an emergent property of changing ecosystem structure over two contrasting semi-arid grass to woody vegetation transitions in New Mexico, USA. Vegetation structure is quantified to evaluate if it can be used to explain observed variations in water, sediment and carbon fluxes. Hydrological connectivity is quantified using a flow length metric, combining topographic and vegetation cover data. Results demonstrate that the two woody-dominated sites have significantly longer mean flowpath lengths (4·3m), than the grass-dominated sites (2·4m). Mean flowpath lengths illustrate a significant positive relationship with the functional response. The woody-dominated sites lost more water, soil and carbon than their grassland counterparts. Woody sites erode more, with mean event-based sediment yields of 1203g, compared to 295g from grasslands. In addition, the woody sites lost more organic carbon, with mean event yields of 39g compared to 5g from grassland sites. Finally, hydrological connectivity (expressed as mean flowpath length) is discussed as a meaningful measure of the interaction between structure and function and how this manifests under the extreme rainfall that occurs in semi-arid deserts. In combination with rainfall characteristics, connectivity emerges as a useful tool to explain the impact of vegetation change on water, soil and carbon losses across semi-arid environments.Copyright © 2013 John Wiley & Sons, Ltd.
Abstract.
Brazier RE (2013). Erosion and Sediment Transport: Finding Simplicity in a Complicated Erosion Model.
, 253-266.
Abstract:
Erosion and Sediment Transport: Finding Simplicity in a Complicated Erosion Model
Problems of erosion and sediment transport are concerned with the same question of how does water interact with sediment to control landscape morphology. This chapter demonstrates how a simplified, or minimum information requirement (MIR) version of water erosion prediction project (WEPP) - MIRSED - can be applied to predict patterns of erosion over a large spatial extent. The results of using this model are evaluated in terms of available observed data. The data are also shown to be highly variable, in space, reflecting the complexity of hillslope-scale erosion processes and the interactions between land use, soil type and topography that controls hillslope erosion. In this chapter, results are generated based upon dominant soil type, distribution of land use and the use of both average slopes and slope distributions from each grid cell across a catchment or region. © 2013 John Wiley & Sons, Ltd.
Abstract.
Peukert S, Bol R, Roberts W, MacLeod CJA, Murray PJ, Dixon ER, Brazier RE (2013). Erratum: Understanding spatial variability of soil properties: a key step in establishing field to farmscale agroecosystem experiments (Rapid Communications in Mass Spectrometry (2012) 26 (2413-2421) DOI: 10.1002/rcm.6336). Rapid Communications in Mass Spectrometry, 27(1).
Scholefield P, Heathwaite AL, Brazier RE, Page T, Schärer M, Beven K, Hodgkinson R, Withers P, Walling D, Haygarth PM, et al (2013). Estimating phosphorus delivery from land to water in headwater catchments using a fuzzy decision tree approach.
Soil Use and Management,
29(SUPPL.1), 175-186.
Abstract:
Estimating phosphorus delivery from land to water in headwater catchments using a fuzzy decision tree approach
The pathway that delivers mobilized phosphorus (P) from source to surface water is conceptually complex. Firstly, P mobilization itself, either through mechanical disturbance of the soil or through chemical dissolution or weathering, is difficult to measure in situ; secondly, the annual flow-weighted mean concentration of P is a difficult metric to gather. Summarizing these pathway processes as the ratio of the delivered P to the mobilized fraction of P assists in the quantification and assessment of the P transfer continuum. The proportion of this mobilized P that is subsequently delivered to the watercourse is also difficult to quantify. A range of P models already exist that aim to predict P mobilization and delivery. Reasonable estimates can be made for the outputs of P from a plot or small catchment over a series of events. Current models mainly rely on empirical data or expert judgment to derive appropriate coefficients of P transfer and delivery. This paper describes the research designed to evaluate the range of delivery coefficients from headwater catchments that might be anticipated for different land-use regions across the UK. These coefficients were evaluated within a fuzzy decision tree framework. The delivery coefficients used in this study covered a broad range of possible values from all available data describing P fluxes from headwater catchments in the UK. The results of this work indicate that delivery coefficients are a useful way of summarizing the mobilization behaviour of a headwater catchment. Mean delivery coefficients above unity were present in four of 18 catchments, indicating higher than average delivery, probably due to intensive agricultural management practices. This first use of a fuzzy or uncertain approach to model P delivery in the UK has generated potentially promising results, and a methodology has been developed for producing delivery coefficients using sparse data, which may be applicable to other headwater catchments. © 2013 the Authors. Soil Use and Management © 2013 British Society of Soil Science.
Abstract.
Grand-Clement E, Anderson K, Smith D, Luscombe D, Gatis N, Ross M, Brazier RE (2013). Evaluating ecosystem goods and services after restoration of marginal upland peatlands in South-West England.
J Appl Ecol,
50(2), 324-334.
Author URL.
Croft H, Anderson K, Brazier RE, Kuhn NJ (2013). Modeling fine-scale soil surface structure using geostatistics.
Water Resources Research,
49(4), 1858-1870.
Abstract:
Modeling fine-scale soil surface structure using geostatistics
There is widespread recognition that spatially distributed information on soil surface roughness (SSR) is required for hydrological and geomorphological applications. Such information is necessary to describe variability in soil structure, which is highly heterogeneous in time and space, to parameterize hydrology and erosion models and to understand the temporal evolution of the soil surface in response to rainfall. This paper demonstrates how results from semivariogram analysis can quantify key elements of SSR for such applications. Three soil types (silt, silt loam, and silty clay) were used to show how different types of structural variance in SSR evolve during simulated rainfall events. All three soil types were progressively degraded using artificial rainfall to produce a series of roughness states. A calibrated laser profiling instrument was used to measure SSR over a 10 cm × 10 cm spatial extent, at a 2 mm resolution. These data were geostatistically analyzed in the context of aggregate breakdown and soil crusting. The results show that such processes are represented by a quantifiable decrease in sill variance, from 7.81 (control) to 0.94 (after 60 min of rainfall). Soil surface features such as soil cracks, tillage lines and erosional areas were quantified by local maxima in semivariance at a given length scale. This research demonstrates that semivariogram analysis can retrieve spatiotemporal variations in soil surface condition; in order to provide information on hydrological pathways. Consequently, geostatistically derived SSR shows strong potential for inclusion as spatial information in hydrology and erosion models to represent complex surface processes at different soil structural scales. © 2013. American Geophysical Union. All Rights Reserved.
Abstract.
Hutton C, Nicholas A, Brazier R (2013). Sub-grid scale parameterization of hillslope runoff and erosion processes for catchment-scale models of semi-arid landscapes. Hydrological Processes
Brazier RE, Krueger T, Wainwright J (2013). Uncertainty Assessment. In (Ed) Patterns of Land Degradation in Drylands, Springer Nature, 265-285.
Peukert S, Bol R, Roberts W, Macleod CJA, Murray PJ, Dixon ER, Brazier RE (2013). Understanding spatial variability of soil properties: a key step in establishing field- to farm-scale agro-ecosystem experiments (vol 26, pg 2413, 2012).
RAPID COMMUNICATIONS IN MASS SPECTROMETRY,
27(1), 284-284.
Author URL.
2012
Old GH, Naden PS, Granger SJ, Bilotta GS, Brazier RE, Macleod CJA, Krueger T, Bol R, Hawkins JMB, Haygarth P, et al (2012). A novel application of natural fluorescence to understand the sources and transport pathways of pollutants from livestock farming in small headwater catchments.
Science of the Total Environment,
417-418, 169-182.
Abstract:
A novel application of natural fluorescence to understand the sources and transport pathways of pollutants from livestock farming in small headwater catchments
This paper demonstrates the application of a low-cost and rapid natural fluorescence technique for tracing and quantifying the transport of pollutants from livestock farming through a small headwater catchment. Fluorescence intensities of Dissolved Organic Matter (DOM) present in different pollutant sources and drainage waters in the Den Brook catchment (Devon, UK) were monitored through storm events occurring between January 2007 and June 2008. Contrasting fluorescence signals from different sources confirmed the technique's usefulness as a tracer of pollutants from livestock farming. Changes in fluorescence intensities of drainage waters throughout storm events were used to assess the dynamics of key pollutant sources. The farmyard area of the catchment studied was shown to contribute polluted runoff at the onset of storm events in response to only small amounts of rain, when flows in the Den Brook first-order channel were low. The application of slurry to a field within the catchment did not elevate the fluorescence of drainage waters during storm events suggesting that when slurry is applied to undrained fields the fluorescent DOM may become quickly adsorbed onto soil particles and/or immobilised through bacterial breakdown. Fluorescence intensities of drainage waters were successfully combined with discharge data in a two component mixing model to estimate pollutant fluxes from key sources during the January 2007 storm event. The farmyard was shown to be the dominant source of tryptophan-like material, contributing 61-81% of the total event flux at the catchment outlet. High spatial and temporal resolution measurements of fluorescence, possibly using novel in-situ fluorimeters, may thus have great potential in quickly identifying and quantifying the presence, dynamics and sources of pollutants from livestock farming in catchments. © 2011 Elsevier B.V.
Abstract.
Krueger T, Quinton JN, Freer J, MacLeod CJA, Bilotta GS, Brazier RE, Hawkins JMB, Haygarth PM (2012). Comparing empirical models for sediment and phosphorus transfer from soils to water at field and catchment scale under data uncertainty.
European Journal of Soil Science,
63(2), 211-223.
Abstract:
Comparing empirical models for sediment and phosphorus transfer from soils to water at field and catchment scale under data uncertainty
Soils are important sources of sediment and phosphorus in rural catchments, necessitating the development of mathematical models for impact assessment. In this paper, multiple empirical models are tested on an event basis at four nested locations in an intensively managed grassland headwater catchment while accounting for parameter and data uncertainties using extended Generalized Likelihood Uncertainty Estimation (GLUE). The study provides the first template of model comparison under data uncertainty in soil erosion and phosphorus transfer modelling as well as hypotheses of soil and water processes in the study catchment. A fodder field, yielding large sediment and phosphorus concentrations in runoff, is characterized by inter-event variation in sediment-discharge relationship, mild intra-event hysteretic behaviour and seemingly random erosion incidents. Sediment-discharge variation is partly formalized by parameter variation as a function of antecedent soil moisture, indicative of a gradual shift from transport- to source-limited behaviour, decreasing soil erodibility and/or decreasing initial flow erosivity and transport capacity with increasing antecedent wetness. The catchment outlet appears to be source-limited while converging flows with different sediment concentrations, variable erosion processes and/or sporadic entrainment of near- or in-stream sediments gain importance. Phosphorus dynamics are strongly linked to those of sediment. Non-linearities can be explained by preferential transfer of phosphorus-rich organic matter at small flows while there is no significant evidence of preferential transfer of phosphorus-rich mineral fines. Iterating between collecting data, constraining uncertainties and rejecting and improving models is suggested as a consistent framework for understanding soil erosion and phosphorus movement. © 2012 the Authors. Journal compilation © 2012 British Society of Soil Science.
Abstract.
Hutton C, Brazier R (2012). Quantifying riparian zone structure from airborne LiDAR: Vegetation filtering, anisotropic interpolation, and uncertainty propagation.
Journal of Hydrology,
442-443, 36-45.
Abstract:
Quantifying riparian zone structure from airborne LiDAR: Vegetation filtering, anisotropic interpolation, and uncertainty propagation
Advances in remote sensing technology, notably in airborne Light Detection and Ranging (LiDAR), have facilitated the acquisition of high-resolution topographic and vegetation datasets over increasingly large areas. Whilst such datasets may provide quantitative information on surface morphology and vegetation structure in riparian zones, existing approaches for processing raw LiDAR data perform poorly in riparian channel environments. A new algorithm for separating vegetation from topography in raw LiDAR data, and the performance of the Elliptical Inverse Distance Weighting (EIDW) procedure for interpolating the remaining ground points, are evaluated using data derived from a semi-arid ephemeral river. The filtering procedure, which first applies a threshold (either slope or elevation) to classify vegetation high-points, and second a regional growing algorithm from these high-points, avoids the classification of high channel banks as vegetation, preserving existing channel morphology for subsequent interpolation (2.90-9.21% calibration error; 4.53-7.44% error in evaluation for slope threshold). EIDW, which accounts for surface anisotropy by converting the remaining elevation points to streamwise co-ordinates, can outperform isoptropic interpolation (IDW) on channel banks, however, performs less well in isotropic conditions, and when local anisotropy is different to that of the main channel. A key finding of this research is that filtering parameter uncertainty affects the performance of the interpolation procedure; resultant errors may propagate into the Digital Elevation Model (DEM) and subsequently derived products, such as Canopy Height Models (CHMs). Consequently, it is important that this uncertainty is assessed. Understanding and developing methods to deal with such errors is important to inform users of the true quality of laser scanning products, such that they can be used effectively in hydrological applications. © 2012 Elsevier B.V.
Abstract.
Puttock A, Dungait JAJ, Bol R, Dixon ER, Macleod CJA, Brazier RE (2012). Stable carbon isotope analysis of fluvial sediment fluxes over two contrasting C<inf>4</inf>-C<inf>3</inf> semi-arid vegetation transitions.
Rapid Communications in Mass Spectrometry,
26(20), 2386-2392.
Abstract:
Stable carbon isotope analysis of fluvial sediment fluxes over two contrasting C4-C3 semi-arid vegetation transitions
RATIONALE: Globally, many drylands are experiencing the encroachment of woody vegetation into grasslands. These changes in ecosystem structure and processes can result in increased sediment and nutrient fluxes due to fluvial erosion. As these changes are often accompanied by a shift from C4 to C3 vegetation with characteristic δ13C values, stable isotope analysis provides a promising mechanism for tracing these fluxes. METHODS: Input vegetation, surface sediment and fluvially eroded sediment samples were collected across two contrasting C4-C3 dryland vegetation transitions in New Mexico, USA. Isotope ratio mass spectrometric analyses were performed using a Carlo Erba NA2000 analyser interfaced to a SerCon 20-22 isotope ratio mass spectrometer to determine bulk δ13C values. RESULTS: Stable isotope analyses of contemporary input vegetation and surface sediments over the monitored transitions showed significant differences (p
Abstract.
Hoang L, Dessai S, Brazier R (2012). Uncertainty analysis of an integrated water system in southern England: Exploring physical and socio-economic uncertainties.
iEMSs 2012 - Managing Resources of a Limited Planet: Proceedings of the 6th Biennial Meeting of the International Environmental Modelling and Software Society, 981-988.
Abstract:
Uncertainty analysis of an integrated water system in southern England: Exploring physical and socio-economic uncertainties
Climate change risk assessment of water resources is fraught with uncertainty. Such uncertainty is not only the accumulation of individual uncertainty components, but also the results of intricate interactions amongst the physical environment and the socio-economic system. There is often a mismatch of model representation of these two systems: while uncertainty of physical factors has often been described using quantitative methods, socio-economic factors have largely been qualitative. In our drought assessment case study, we evaluate uncertainty in the physical factors and demand responses in the context of climate change. In particular, we focus on structural uncertainty of the supply component and data uncertainty of the demand component. To explore structural uncertainty, a model of fine scale that has nodes representing real supply and demand sources was used as a reference model; another model at the water resource zone scale was used as an emulator to reflect information loss if a coarser spatial resolution is used. The input data are the UK Climate Projections 2009, 1989-2011 historic demand and 1961-1990 historic climate data. The main model output of interest is failure of supply. We found that uncertainty from the hydrological model contributes a high uncertainty margins to the final model results; in this case study it is more influential than uncertainty from either projected climate change or demand growth.
Abstract.
Peukert S, Bol R, Roberts W, Macleod CJA, Murray PJ, Dixon ER, Brazier RE (2012). Understanding spatial variability of soil properties: a key step in establishing field- to farm-scale agro-ecosystem experiments.
Rapid Communications in Mass Spectrometry,
26(20), 2413-2421.
Abstract:
Understanding spatial variability of soil properties: a key step in establishing field- to farm-scale agro-ecosystem experiments
RATIONALE: the spatial variability of soil properties is poorly understood, despite its importance in designing appropriate experimental sampling strategies. As preparation for a farm-scale agro-ecosystem services monitoring project, the 'North Wyke Farm Platform', there was a need to assess the spatial variability of key soil chemical and physical properties. METHODS: the field-scale spatial variability of soil chemical (total N, total C, soil organic matter), soil physical properties (bulk density and particle size distribution) and stable isotope ratios (δ13C and δ15N values) was studied using geostatistical approaches in an intensively managed grassland. RESULTS: the scales over which stable isotopes vary (ranges: 212-258 m) were larger than those of the total nutrients, soil organic matter and bulk density (ranges: 84-170 m). Two visually and statistically distinct areas of Great Field (north and south) were identified in terms of co-occurring high/low values of several soil properties. CONCLUSIONS: the resulting patterns of spatial variability suggest lower spatial variability of stable isotopes than that of total nutrients, soil organic matter and bulk density. Future sampling regimes should be conducted in a grid with 5 years) on the patterns of spatial variability. Copyright © 2012 John Wiley & Sons, Ltd.
Abstract.
2011
Quinton JN, Krueger T, Freer J, Brazier RE, Bilotta GS (2011). A Case Study of Uncertainty: Applying GLUE to EUROSEM. , 80-97.
Deasy C, Baxendale SA, Ridall G, Heathwaite AL, Hodgkinson R, Brazier RE (2011). Advancing understanding of runoff and sediment transfers in agricultural catchments. through simultaneous observations across scales. Earth Surface Processes and Landforms
Beven KJ, Brazier RE (2011). Dealing with uncertainty in erosion model predictions. , 52-79.
Cerda A, Brazier RE, de Vente J, Nearing MA (2011). Scales and erosion. Catena
Brazier RE, Hutton CJ, Parsons AJ, Wainwright J (2011). Scaling Soil Erosion Models in Space and Time. , 98-116.
2010
Bilotta G, Brazier RE, Krueger T, Butler P, Freer J, Hawkins J, Macleod CJA, Haygarth PM, Quinton J (2010). Assessing Catchment-Scale Erosion and Yields of Suspended Solids from Improved Temperate Grassland. Journal of Environmental Monitoring
Granger S, Bol R, Dixon L, Naden P, Old G, Marsh J, Brazier RE, Bilotta G, White S, Haygarth PM, et al (2010). Assessing multiple novel tracers to improve the understanding of the contribution of agricultural farm waste to diffuse water pollution. Journal of Environmental Monitoring
Turnbull L, Brazier RE, Wainwright J (2010). Biotic and abiotic changes in ecosystem structure over a shrub-encroachment gradient in the southwestern USA. Ecosystems
Turnbull L, Wainwright J, Brazier RE (2010). Changes in hydrology and erosion over a transition from grassland to shrubland.
HYDROL PROCESS,
24(4), 393-414.
Abstract:
Changes in hydrology and erosion over a transition from grassland to shrubland
The degradation of grasslands is a common problem across semi-arid areas worldwide. Over the last 150 years, much of the south-western United States has experienced significant land degradation, with desert grasslands becoming dominated by shrubs and concurrent changes in runoff and erosion which are thought to propagate further the process of degradation. Plot-based experiments to determine how spatio-temporal characteristics of soil moisture, runoff and erosion change over a transition from grassland to shrubland were carried out at four sites over a transition from black grama (Bouteloua eriopoda) grassland to creosotebush (Larrea tridentata) shrubland at the Sevilleta NWR LTER site in New Mexico. Each site consisted of a 10 x 30 m bounded runoff plot and adjacent characterization plots with nested sampling points where soil moisture content was measured. Results show distinct spatio-temporal variations in soil moisture content, which are due to the net effect of processes operating at multiple spatial and temporal scales, such as plant uptake of water at local scales versus the redistribution of water during runoff events at the hillslope scale. There is an overall increase in runoff and erosion over the transition from grassland to shrubland, which is likely to be associated with an increase in connectivity of bare, runoff-generating areas, although these increases do not appear to follow a linear trajectory. Erosion rates increased over the transition from grassland to shrubland, likely related in part to changes in runoff characteristics and the increased capacity of the runoff to detach, entrain and transport sediment. Over all plots, fine material was preferentially eroded which has potential implications for nutrient cycling since nutrients tend to be associated with fine sediment. Copyright (C) 2009 John Wiley & Sons, Ltd.
Abstract.
Pilgrim ES, Macleod CJA, Blackwell MSA, Bol R, Hogan DV, Chadwick DR, Cardenas L, Misselbrook TH, Haygarth PM, Brazier RE, et al (2010). Chapter four Interactions Among Agricultural Production and Other Ecosystem Services Delivered from European Temperate Grassland Systems. In (Ed) , Elsevier, 117-154.
Granger SJ, Hawkins JMB, Bol R, White SM, Naden P, Old G, Bilotta GS, Brazier RE, MacLeod CJA, Haygarth PM, et al (2010). High temporal resolution monitoring of multiple pollutant responses in drainage from an intensively managed grassland catchment caused by a summer storm.
Water, Air, and Soil Pollution,
205(1-4), 377-393.
Abstract:
High temporal resolution monitoring of multiple pollutant responses in drainage from an intensively managed grassland catchment caused by a summer storm
This work presents data on a suite of diffuse pollutants, monitored in a stream draining an intensively managed grassland on a 30 min time step during a period of intense rainfall to better understand their sources and pathways. Nitrite (92 μg l-1), particulate phosphorus (107 μg l -1) and soluble phosphorus (74 μg l-1) exceeded environmental limits during base flow. Concentrations of nitrate and nitrite were decreased during the storm event, whereas all other pollutants generally increased and exceeded environmental limits where specified, especially when associated with a small subsidiary hydrograph on the rising limb of the main hydrograph. Total pollutants loads, when using a 60 min sampling frequency, would have led to significant over and under-estimations depending on which 60 min sample set was used. In the worst case, loads of ammonium could have been under-estimated by 35% or over estimated by 25% with errors being associated with loads on the rising limb of the hydrograph and more specifically a small subsidiary hydrograph. This subsidiary hydrograph may have occurred as a result of runoff from the farm hard standings within the catchment. Incidental transfer of pollutants associate with this runoff have masked the overall grassland pollutant response. To better understand these different source areas and pollutant dynamics, there is a need for novel tracing techniques to elucidate their relative contribution and pathways. © 2009 Springer Science+Business Media B.V.
Abstract.
Turnbull L, Wainwright J, Brazier RE (2010). Hydrology, erosion and nutrient transfers over a transition from semi-arid grassland to shrubland in the South-Western USA: a modelling assessment.
Journal of Hydrology,
388(3-4), 258-272.
Abstract:
Hydrology, erosion and nutrient transfers over a transition from semi-arid grassland to shrubland in the South-Western USA: a modelling assessment
Land degradation in arid and semi-arid areas, as a consequence of the invasion of grasslands by shrubs, is often associated with an increase in runoff and erosion and a change in nutrient transport. Modelling of nutrient transport during runoff events (in particular particulate-bound nutrients), is especially important, since the spatial redistribution of nutrients (in addition to water and sediment) can have significant implications for vegetation dynamics in these ecosystems. In this study, Mahleran (Model for Assessing Hillslope to Landscape Erosion Runoff, and Nutrients) is extensively evaluated against runoff and erosion data from four plots (representative of different stages of land degradation) over a transition from grassland to shrubland, at the Sevilleta National Wildlife Refuge in New Mexico, USA. A new particulate-bound nutrient module was developed to include a representation of particulate-bound nutrient dynamics, which is an important form of nutrient transport in these ecosystems. Understanding dynamics of both dissolved and particulate-bound nutrient dynamics during runoff events is imperative, because of their differing roles in terms of nutrient bioavailability and potential implications for plant dynamics. Results of the model evaluation show that the runoff and erosion components of Mahleran perform reasonably well, as does the new particulate-bound nutrient sub-model, though not consistently. Performance of the particulate-bound nutrient model was better for the end-member plots, because of better parameterization data available for end-member vegetation types. Since the particulate-bound nutrient sub-model is by necessity strongly dependent on the simulated erosion rate, the performance of the particulate-bound nutrient model is dependent on the performance of the erosion component of Mahleran, so that when erosion is well represented by the model, so typically are particulate nutrient transfers. The performance of the dissolved nutrient component of Mahleran was poor in this application, which indicates that the process representation for this semi-arid environment and the parameterisation of the dissolved nutrient component were inadequate. Results from the model evaluation suggest that an improved understanding of dissolved nutrient dynamics during runoff events and simulation if inter-event nutrient dynamics is required, in order to improve the level of process representation within modelling approaches and thus the ability to simulate dissolved nutrient dynamics and their subsequent effects on other ecosystem processes. © 2010 Elsevier B.V. All rights reserved.
Abstract.
Wainwright J, Tunrbull L, Ibrahim TG, Lexartza-Artza I, Thornton SF, Brazier RE (2010). Linking Environmental Régimes, Space and Time: Interpretations of Structural and Functional Connectivity. Geomorphology
Turnbull L, Wainwright J, Brazier RE (2010). Nitrogen and Phosphorus dynamics during runoff events over a transition from grassland to shrubland in South Western USA. Hydrological Processes
Wainwright J, Parsons AJ, Müller EN, Brazier RE, Powell DM (2010). Standing Proud: a Response to “Soil-Erosion Models: Where do we Really Stand?” by Smith et al. Earth Surface Processes and Landforms
2009
Beven KJ, Brazier RE (2009). Dealing with uncertainty in soil erosion modelling. In Morgan RPC, Nearing MA (Eds.) The handbook of soil erosion modelling.
Quinton JN, Krueger T, Freer J, Bilotta GS, Brazier RE (2009). EUROSEM: an Evaluation of the dynamic capability of the EUROSEM model using GLUE. In Morgan RPC, Nearing MA (Eds.) The handbook of soil erosion modelling.
Krueger T, Quinton J, Freer J, Macleod CJA, Bilotta GS, Brazier RE, Butler P, Granger S, Haygarth PM (2009). Ensemble evaluation of hydrological model hypotheses. Water Resources Research
Brazier RE, Haygarth PM, Macleod CJA, Butler P, Hawkins J, Worsfold P, Bilotta G, Gimbert L, Granger S, Naden P, et al (2009). Final Report to Defra Project PE0120 – Phosphorus mobilisation with sediment and colloids through drained and undrained grasslands.
Deasy C, Brazier RE, Heathwaite AL, Hodgkinson R (2009). Pathways of runoff and sediment transfer in small agricultural catchments. Hydrological Processes, 23((9)), 1349-1358.
Wainwright J, Parsons AJ, Müller EN, Brazier RE, Powell DM (2009). Response to Hairsine's and Sander's Comment on 'A transport-distance based approach to scaling erosion rates:' Parts 1, 2 and 3 by Wainwright et al. 2008. Earth Surface Processes and Landforms
wainwright J, parsons A, Brazier RE, Muller EN, Powell DM (2009). Response to Hairsine’s and Sander’s ‘Comment
on “A transport-distance based approach to
scaling erosionrates”: Parts 1, 2 and 3 by
Wainwright et al.’. Earth Surface Processes and Landforms
Wainwright J, Parsons AJ, Müller EN, Brazier RE, Powell DM (2009). Response to Kinnell's 'Comment on "A transport-distance approach to scaling erosion rates: III. Evaluating scaling characteristics of Mahleran"'. Earth Surface Processes and Landforms, 34(9), 1320-1321.
Brazier RE, Hutton C, Parsons AJ, Wainwright J (2009). Scaling issues in soil erosion modelling. In Morgan RPC, Nearing MA (Eds.) The handbook of soil erosion modelling.
Krueger T, Quinton JN, Freer J, Macleod CJA, Bilotta GS, Brazier RE, Butler P, Haygarth PM (2009). Uncertainties in data and models to describe event dynamics of agricultural sediment and phosphorus transfer.
J Environ Qual,
38(3), 1137-1148.
Abstract:
Uncertainties in data and models to describe event dynamics of agricultural sediment and phosphorus transfer.
Mathematical models help to quantify agricultural sediment and phosphorus transfers and to simulate mitigation of pollution. This paper develops empirical models of the dominant sediment and phosphorus event dynamics observed at high resolution in a drained and undrained, intensive grassland field-scale lysimeter (1 ha) experiment. The uncertainties in model development and simulation are addressed using Generalized Likelihood Uncertainty Estimation. A comparison of suspended solids (SS) and total phosphorus (TP) samples with a limited number of manual repeats indicates larger data variability at low flows. Quantitative uncertainty estimates for discharge (Q) are available from another study. Suspended solids-discharge (SS-Q) hysteresis is analyzed for four events and two drained and two undrained fields. Hysteresis loops differ spatially and temporally, and exhaustion is apparent between sequential hydrograph peaks. A coherent empirical model framework for hysteresis, where SS is a function of Q and rate of change of Q, is proposed. This is evaluated taking the Q uncertainty into account, which can contribute substantially to the overall uncertainty of model simulations. The model simulates small hysteresis loops well but fails to simulate exhaustion of SS sources and flushing at the onset of events. Analysis of the TP-SS relationship reveals that most of the variability occurs at low flows, and a power-law relationship can explain the dominant behavior at higher flows, which is consistent across events, fields, and pathways. The need for further field experiments to test hypotheses of sediment mobilization and to quantify data uncertainties is identified.
Abstract.
Author URL.
2008
Turnbull L, Wainwright J, Brazier RE (2008). A conceptual framework for understanding semi-arid land degradation: ecohydrological interactions across multiple-space and time scales.
ECOHYDROLOGY,
1(1), 23-34.
Abstract:
A conceptual framework for understanding semi-arid land degradation: ecohydrological interactions across multiple-space and time scales
Land degradation is a problem prolific across semi-arid areas worldwide. Despite being a complex process including both biotic and abiotic elements, previous attempts to understand ecosystem dynamics have largely been carried out within disparate disciplines of ecology and hydrology, which has led to significant limitations. Here, an ecohydrological framework is outlined. to provide a new direction for the study of land degradation in semi-arid ecosystem. Unlike other frameworks that draw upon hierarchy theory to provide a board, non-explicit conceptual framework is based upon the explicit linkage of process operating over the continuum of temporal and spatial scales by perceiving the ecosystem as a series of structural and functional connections, within which interactions between biotic and abiotic components of the landscape occur. It is hypothesized that semi-arid land degradation conforms to a cusp-catastrophe model in which the two controlling variables are abiotic structural connectivity and abiotic functional connectivity, which implicitly account for ecosystem resilience, and biotic structural and function connectivity. It is suggest therefore that future research must (1) evaluate how abiotic and biotic function (i.e. water, sediment and nutrient loss/redistribution) vary over grass-shrub transitions and (2) quantify the biotic/abiotic structure over grass-shrub transitions, to (3) determine the interactions between ecosystem structure and function. and interaction/feedbacks between biotic and abiotic components of the ecosystem. Copyright (C) 2008 John Wiley & Sons, Ltd.
Abstract.
Deasy C, Heathwaite AL, Brazier RE (2008). A field methodology for quantifying phosphorus transfer and delivery to streams in first order agricultural catchments.
J HYDROL,
350(3-4), 329-338.
Abstract:
A field methodology for quantifying phosphorus transfer and delivery to streams in first order agricultural catchments
An understanding of the relative importance of different hydrological pathways in phosphorus delivery from land to water is currently constrained by a lack of appropriate methods available to quantify the delivery process. New monitoring tools are needed which will provide a framework for understanding phosphorus (P) transfer and delivery at a range of scales in agricultural catchments. A field methodology incorporating the techniques of event-based, on-site observation and sampling within a flexible, non-plot based structure is described and applied to a first order stream catchment in Southern England, UK. The results show that P transfers to the stream reach monitored were dominated by inputs from one field drain, and that overland flow inputs, despite being directly connected to the stream and containing higher P concentrations (maximum 3708 mu g l(-1)), contributed less to the stream P flux. The processes of P transfer and delivery to the stream were complex, changing both within flow pathways and temporally over an event. (C) 2007 Elsevier B.V. All rights reserved.
Abstract.
Wainwright J, Parsons AJ, Muller EN, Brazier RE, Powell DM, Fenti B (2008). A transport-distance approach to scaling erosion rates: 2. Sensitivity and evaluation of MAHLERAN.
EARTH SURF PROC LAND,
33(6), 962-984.
Abstract:
A transport-distance approach to scaling erosion rates: 2. Sensitivity and evaluation of MAHLERAN
In the first paper in this series, we demonstrated that most process-based erosion models have a series of in-built assumptions that led us to question their true process basis. An alternative soil-erosion model (MAHLERAN - Model for Assessing Hilislope-Landscape Erosion, Runoff and Nutrients) based upon particle-travel distance has been presented in the first paper in this series and this paper presents the first of two evaluations of the model. Here, a sensitivity analysis shows that the numerical model is consistent with the analytical model of Parsons et al. (2004) and demonstrates that downslope patterns of sediment flux on hillslopes are a complex interaction of rainfall intensity, duration and pattern; hillslope gradient; surface roughness and sediment size. This result indicates that the spatial scaling of sediment transfers on hillslopes is a non-trivial problem and will vary from point to point and from event to event and thus from year to year. The model is evaluated against field data from a rainfall-simulation experiment on an 18 m x 35 m plot for which there are sub-plot-scale data on runoff hydraulics and sediment flux. The results show that the model is capable of reproducing the sedigraph with an overall normalized root-mean-square error of 18-4% and Nash-Sutcliffe efficiency of 0-90. Spatial and temporal patterns of particle-size distributions of the eroded sediment are also reproduced very well, once erosion parameters have been optimized for the specific soil conditions. Copyright (C) 2008 John Wiley & Sons, Ltd.
Abstract.
Wainwright J, Parsons AJ, Muller EN, Brazier RE, Powell DM, Fenti B (2008). A transport-distance approach to scaling erosion rates: 3. Evaluating scaling characteristics of MAHLERAN.
EARTH SURF PROC LAND,
33(7), 1113-1128.
Abstract:
A transport-distance approach to scaling erosion rates: 3. Evaluating scaling characteristics of MAHLERAN
In the two previous papers of this series, we demonstrated how a novel approach to erosion modelling (MAHLERAN - Model for Assessing Hillslope-Landscape Erosion, Runoff and Nutrients) provided distinct advantages in terms of process representation and explicit scaling characteristics when compared with existing models. A first evaluation furthermore demonstrated the ability of the model to reproduce spatial and temporal patterns of erosion and their particle-size characteristics on a large rainfall-simulation plot. In this paper, we carry out a more detailed evaluation of the model using monitored erosion events on plots of different size. The evaluation uses four plots of 2101, 115.94, 56.84 and 302.19 m(2), with lengths of 4.12, 14.48, 18.95 and 27.78 m, respectively, on similar soils to the rainfall-simulation plot, for which runoff and erosion were monitored under natural rainfall. Although the model produces the correct ranking of the magnitude of erosion events, it performs less well in reproducing the absolute values and particle-size distributions of the eroded sediment. The implications of these results are evaluated in terms of requirements for process understanding and data for parameterization of improved soil-erosion models. We suggest that there are major weaknesses in the current understanding and data underpinning existing models. Consequently, a more holistic re-evaluation is required that produces functional relationships for different processes that are mutually consistent, and that have appropriate parameterization data to support their use in a wide range of environmental conditions. Copyright (C) 2008 John Wiley & Sons, Ltd.
Abstract.
Wainwright J, Parsons AJ, Muller EN, Brazier RE, Powel DM, Fenti B (2008). A transport-distance approach to scaling erosion rates: I. Background and model development.
EARTH SURF PROC LAND,
33(5), 813-826.
Abstract:
A transport-distance approach to scaling erosion rates: I. Background and model development
The process basis of existing soil-erosion models is shown to be ill-founded. The existing literature builds directly or indirectly on Bennett's (1974) paper, which provided a blueprint for integrated catchment-scale erosion modelling. Whereas Bennett recognized the inherent assumptions of the approach suggested, subsequent readings of the paper have led to a less critical approach. Most notably, the assumption that sediment movement could be approximated by a continuity equation that related to transport in suspension has produced a series of submodels that assume that all movement occurs in suspension. For commonly occurring conditions on hilislopes, this case is demonstrably untrue both on theoretical grounds and from empirical observations. Elsewhere in the catchment system, it is only partially true, and the extent to which the assumption is reasonable varies both spatially and temporally. A second ground-breaking paper - that of Foster and Meyer (1972) - was responsible for subsequent uncritical application of a first-order approximation to deposition based on steady-state analysis and again a weak empirical basis. We describe in this paper an alternative model (MAHLERAN - Model for Assessing Hillslope-Landscape Erosion, Runoff and Nutrients) based upon particle-travel distance that overcomes existing limitations by incorporating parameterizations of the different detachment and transport mechanisms that occur in water erosion in hilislopes and small catchments. In the second paper in the series, we consider the sensitivity and general behaviour of MAHLERAN, and test it in relation to data from a large rainfall-simulation experiment. The third paper of the sequence evaluates the model using data from plots of different sizes in monitored rainfall events. From this evaluation, we consider the scaling characteristics of the current form of MAHLERAN and suggest that integrated modelling, laboratory and field approaches are required in order to advance the state of the art in soil-erosion modelling. Copyright (c) 2008 John Wiley & Sons, Ltd.
Abstract.
Parsons AJ, Wainwright J, Brazier RE, Powell DM (2008). Is sediment delivery a fallacy? Reply. Earth Surface Processes and Landforms, 33(10), 1630-1631.
Quinton JN, Brazier RE (2008). Letter to the Editor. SOIL USE MANAGE, 24(4), 427-428.
Bilotta GS, Brazier RE, Haygarth PM, Macleod CJA, Butler P, Granger S, Krueger T, Freer J, Quinton J (2008). Rethinking the contribution of drained and undrained grasslands to sediment-related water quality problems.
J Environ Qual,
37(3), 906-914.
Abstract:
Rethinking the contribution of drained and undrained grasslands to sediment-related water quality problems.
Grass vegetation has been recommended for use in the prevention and control of soil erosion because of its dense sward characteristics and stabilizing effect on the soil. A general assumption is that grassland environments suffer from minimal soil erosion and therefore present little threat to the water quality of surface waters in terms of sediment and sorbed contaminant pollution. Our data question this assumption, reporting results from one hydrological year of observations on a field-experiment monitoring overland flow, drain flow, fluxes of suspended solids, total phosphorus (TP), and molybdate-reactive phosphorus (
Abstract.
Author URL.
parsons A, wainwright J, Brazier RE, powell D (2008). Scale relationships in hillslope runoff and erosion
Reply. Earth Surface Processes and Landforms, 33, 1637-1638.
Bilotta GS, Brazier RE (2008). Understanding the influence of suspended solids on water quality and aquatic biota.
WATER RES,
42(12), 2849-2861.
Abstract:
Understanding the influence of suspended solids on water quality and aquatic biota
Over the last 50 years the effects of suspended solids (SS) on fish and aquatic life have been studied intensively throughout the world. It is now accepted that SS are an extremely important cause of water quality deterioration leading to aesthetic issues, higher costs of water treatment, a decline in the fisheries resource, and serious ecological degradation of aquatic environments. As such, government-led environmental bodies have set recommended water quality guidelines for concentrations of SS in freshwater systems. However, these reference values are often spurious or based on the concept of turbidity as a surrogate measure of the concentration of SS. The appropriateness of these recommended water quality values is evaluated given: (1) the large variability and uncertainty in data available from research describing the effects of SS on aquatic environments, (2) the diversity of environments that these values are expected to relate to, and (3) the range of conditions experienced within these environments. Furthermore, we suggest that reliance solely upon turbidity data as a surrogate for SS must be treated with caution, as turbidity readings respond to factors other than just concentrations of SS, as well as being influenced by the particle-size distribution and shape of SS particles. in addition, turbidity is a measure of only one of the many detrimental effects, reviewed in this paper, which high levels of SS can have in waterbodies. in order to improve the understanding of the effects of SS on aquatic organisms, this review suggests that: First, high-resolution turbidity monitoring should be supplemented with direct, measurements of SS (albeit at lower resolution due to resource issues). This would allow the turbidity record to be checked and calibrated against SS, effectively building a rating-relationship between SS and turbidity, which would in-turn provide a clearer picture of the exact magnitude of the SS problem. Second, SS should also be characterised in terms of their particle-size distribution and chemical composition. This would provide information to develop a more comprehensive understanding of the observed variable effects of a given concentration of SS in aquatic habitats. These two suggested improvements, combined with lower-resolution concurrent measures of aquatic ecological status, would improve our understanding of the effects of SS in aquatic environments and together with a more detailed classification of aquatic environments, would provide an environment-specific evidence base for the establishment of effective water quality guidelines for SS. (C) 2008 Elsevier Ltd. All rights reserved.
Abstract.
Turnbull L, Brazier RE, Wainwright J, Dixon L, Bol R (2008). Use of carbon isotope analysis to understand semi-arid erosion dynamics and long-term semi-arid land degradation.
RAPID COMMUNICATIONS IN MASS SPECTROMETRY,
22(11), 1697-1702.
Abstract:
Use of carbon isotope analysis to understand semi-arid erosion dynamics and long-term semi-arid land degradation
Many semi-arid areas worldwide are becoming degraded, in the form of C-4 grasslands being replaced by C-3 shrublands, which causes an increase in surface runoff and erosion, and altered nutrient cycling, which may affect global biogeochemical cycling. The prevention or control of vegetation transitions is hindered by a lack of understanding of their temporal and spatial dynamics, particularly in terms of interactions between biotic and abiotic processes. This research investigates (1) the effects of soil erosion on the delta C-13 values of soil organic matter (SOM) throughout the soil profile and its implications for reconstructing vegetation change using carbon-isotope analysis and (2) the spatial properties of erosion over a grass-shrub transition to increase understanding of biotic-abiotic interactions by using delta C-13 signals of eroded material as a sediment tracer. Results demonstrate that the soils over grass-shrub transitions are not in steady state. A complex interplay of factors determines the input of SOM to the surface horizon of the soil and its subsequent retention and turnover through the soil profile. A positive correlation between event runoff and delta C-13 signatures of eroded sediment was found in all plots. This indicates that the delta C-13 signatures of eroded sediment may provide a means of distinguishing between changes in erosion dynamics over runoff events of different magnitudes and over different vegetation types. The development of this technique using delta C-13 signatures of eroded sediment provides a new means of furthering existing understanding of erosion dynamics over vegetation transitions. This is critical in terms of understanding biotic-abiotic feedbacks and the evolution of areas subject to vegetation change in semi-arid environments. Copyright (C) 2008 John Wiley & Sons, Ltd.
Abstract.
2007
Brazier RE, Bilotta GS, Haygarthz PM (2007). A perspective on the role of lowland, agricultural grasslands in contributing to erosion and water quality problems in the UK. EARTH SURF PROC LAND, 32(6), 964-967.
Bilotta GS, Brazier RE, Haygarth PM (2007). Processes affecting transfer of sediment and colloids, with associated phosphorus, from intensively farmed grasslands: Erosion. Hydrological Processes, 21(1), 135-139.
Deasy C, Brazier RE, Heathwaite AL, Hodgkinson R (2007). Scale-related sediment and phosphorus transfers in small agricultural catchments.
IAHS-AISH Publication(314), 79-89.
Abstract:
Scale-related sediment and phosphorus transfers in small agricultural catchments
Abstract Gaining a better understanding of the processes and linkages operating in agricultural catchments is essential in understanding how diffuse sources of pollution influence the water quality of fluvial systems. One of the key limitations is the lack of available data at a range of spatial scales, which is necessary in order to improve process understanding and model develop ment. Carefully designed field-based research has the potential to improve predictions of water quality in agricultural catchments, which is particularly important given the context of changing climate and land use. Event-based fluxes of sediment and phosphorus were monitored at different scales in a first-order agricultural catchment in Herefordshire, UK, and the data have enabled characterisation of their behaviour and identification of relationships at various scales from hillslope patches of 60 m length to a 30 ha first-order catchment. The results shown here indicate the differing behaviour of both sediment and phosphorus over six events throughout two hydrological years between two scales of observation: the hillslope and the catchment. Copyright © 2007 IAHS Press.
Abstract.
Powell DM, Brazier R, Parsons A, Wainwright J, Nichols M (2007). Sediment transfer and storage in dryland headwater streams.
GEOMORPHOLOGY,
88(1-2), 152-166.
Abstract:
Sediment transfer and storage in dryland headwater streams
This study describes the dynamics of sediment transfer and storage in three headwater channels of the Walnut Gulch Watershed in the Chihuahuan Desert, southeastern Arizona, USA. Spatially distributed information on volumes of stream-bed scour and fill and the resultant net changes in sediment storage was collected from three channel reaches using dense arrays of scour chains. Reach-averaged estimates of volumetric scour for individual events ranged between 0.001 and 0.11 m(3) m(-2). Scour volumes combine with relatively little scatter when rated against peak unit stream power demonstrating that flood magnitude accounts for much of the variance. As a result of locally compensating scour and fill, net changes in sediment storage during individual events were small. Because aggradation and degradation fluctuated with no persistent temporal trend over the study period, sediment transfers through the reaches were not significantly affected by movement of sediment into or out of storage. Measurements of the volume of sediment trapped in a stock-pond downstream of the study sites suggest that scoured bed material travelled several hundred m year(-1) with a virtual velocity of about 350 m h(-1). (C) 2006 Elsevier B.V. All rights reserved.
Abstract.
Bilotta GS, Brazier RE, Haygarth PM (2007). The Impacts of Grazing Animals on the Quality of Soils, Vegetation, and Surface Waters in Intensively Managed Grasslands.
Advances in Agronomy,
94, 237-280.
Abstract:
The Impacts of Grazing Animals on the Quality of Soils, Vegetation, and Surface Waters in Intensively Managed Grasslands
This chapter provides a comprehensive review of the literature relating to the impacts of grazing animals on the quality of soils, vegetation, and surface waters. It focuses on intensively managed grasslands where there is the greatest potential for these impacts to be observed. The chapter indicates that while well-managed grazing can be beneficial to the environment, intensively managed grazing can actually lead to the degradation of both the soil and vegetation of grassland environments. The various causes, forms, and consequences of this degradation are discussed in detail, and gaps in the knowledge are identified. The chapter highlights the need for recognition and quantification of the relationships between the on-site impacts of grazing animals (i.e. changes in soil properties and vegetation cover) and the off-site impacts of grazing animals (i.e. the impact of these changes on hydrology and water quality in surface waters), as these relationships have, in the past, only been alluded to by authors. However, there exists relatively little research evidence to support and quantify these relationships, thus herein we describe data required to address the lack of understanding of the role of grazing animals on grasslands. Finally, the last section of this chapter considers the land management and remediation options available for the reduction of the impacts of intensive livestock farming. © 2006 Elsevier Inc. All rights reserved.
Abstract.
Brazier RE, Parsons AJ, Powell DM, Wainwright J (2007). Upscaling understanding of nitrogen dynamics associated with overland flow in a semi-arid environment. Biogeochemistry, 82(3), 265-278.
Liu S, Butler D, Brazier R, Heathwaite L, Khu ST (2007). Using genetic algorithms to calibrate a water quality model.
Sci Total Environ,
374(2-3), 260-272.
Abstract:
Using genetic algorithms to calibrate a water quality model.
With the increasing concern over the impact of diffuse pollution on water bodies, many diffuse pollution models have been developed in the last two decades. A common obstacle in using such models is how to determine the values of the model parameters. This is especially true when a model has a large number of parameters, which makes a full range of calibration expensive in terms of computing time. Compared with conventional optimisation approaches, soft computing techniques often have a faster convergence speed and are more efficient for global optimum searches. This paper presents an attempt to calibrate a diffuse pollution model using a genetic algorithm (GA). Designed to simulate the export of phosphorus from diffuse sources (agricultural land) and point sources (human), the Phosphorus Indicators Tool (PIT) version 1.1, on which this paper is based, consisted of 78 parameters. Previous studies have indicated the difficulty of full range model calibration due to the number of parameters involved. In this paper, a GA was employed to carry out the model calibration in which all parameters were involved. A sensitivity analysis was also performed to investigate the impact of operators in the GA on its effectiveness in optimum searching. The calibration yielded satisfactory results and required reasonable computing time. The application of the PIT model to the Windrush catchment with optimum parameter values was demonstrated. The annual P loss was predicted as 4.4 kg P/ha/yr, which showed a good fitness to the observed value.
Abstract.
2006
Parsons AJ, Wainwright J, Brazier RE (2006). A conceptual model for sediment and nutrient fluxes from rural land. International Journal of Biodiversity Science and Management, 2, 1-3.
Parsons AJ, Brazier RE, Wainwright J (2006). A conceptual model for sediment and nutrient fluxes from rural land. International Journal of Biodiversity Science and Management, 2(3), 232-234.
Brazier R, Schärer M, Heathwaite L, Beven K, Scholefield P, Haygarth P, Hodgkinson R, Walling D, Withers P (2006). A framework for predicting delivery of phosphorus from agricultural land using a decision-tree approach. In (Ed)
, 514-523.
Abstract:
A framework for predicting delivery of phosphorus from agricultural land using a decision-tree approach
Abstract.
Parsons AJ, Wainwright J, Brazier RE, Powell DM (2006). Is sediment delivery a fallacy?. Earth Surface Processes and Landforms, 31, 1325-1328.
Brazier RE, Schärer M, Heathwaite AL, Beven KJ, Scholefield P, Haygarth PM, Walling DE, Withers P, Hodgkinson R (2006). Predicting delivery of phosphorus from agricultural land using a decision-tree approach. In (Ed) IAHS Red Book, Dundee.
Haygarth PM, Bilotta GS, Bol R, Brazier RE, Butler PJ, Freer J, Gimbert LJ, Granger SJ, Krueger T, Macleod CJA, et al (2006). Processes affecting transfer of sediment and colloids, with associated phosphorus, from intensively farmed grasslands: an overview of key issues.
Hydrological Processes,
20(20), 4407-4413.
Abstract:
Processes affecting transfer of sediment and colloids, with associated phosphorus, from intensively farmed grasslands: an overview of key issues
We consider that here are four key issues and priorities for hydrological sciences in respect to sidement, phosphorus and colloid transfers from intensive grasslands (Table I). These are inadequate inventories, analytical challenges, the neglected role of organic matter and challenges for modelling and integration. We need to change the way in which grassland systems are perceived and monitored; this commentary and the ones that follow may help start to achieve this. There is also a critical requirement for a wider acceptance of a 'continuum' of sediment and particles and processes from molecular to >1 μm, including clarity with operational definitions and an acceptance of the strenghts and weakness of analytical tools. A variety of new tracer techniques are avaliable for helping assess the role of organic matter in contributing to transfers and these must be applied. Field scientists must fully appreciate the variability of observations, and modellers need to understand the uncertainty in model processes and model outputs. Overall, however, the critical message is that integrated inter-disciplinary team working is encourage, discipline polarization is discourage because it undermines progress. To that end, in the assembly of commentaries that follow (Bilotta et al. 2007; Gimbert et al. 2007; Granger et al.; 2007; Krueger et al. 2007) we are presenting ideas as part of an integrated project team that is attempting to improve our knowledge and ability to model sediment, colloids and phosphorus losses from intensive grassland, with - we hope - some wider generic relevance for the hydrological community. Copyright © 2006 John Wiley & Sons, Ltd.
Abstract.
Parsons AJ, Brazier RE, Powell DM, Wainwright J (2006). Scale relationships in hillslope runoff and erosion. Earth Surface Processes and Landforms, 31(11), 1384-1393.
Powell DM, Brazier RE, Wainwright J, Parsons AJ (2006). Spatial patterns of streambed scour, fill and channel change in sand-bed rivers. Water Resources Research, 42
Brazier RE, Parsons AJ, Wainwright J, Powell DM, Schlesinger W (2006). Understanding the Effects of Spatial Scale on Nutrient Dynamics Associated with Overland Flow in Semi-Arid Environments. In (Ed) Water management and Soil Conservation in Semi-Arid Environments, International Soil Conservation Organisation.
2005
Heathwaite AL, Brazier RE, Dils R, Liu S, Carvahlo L, Pope L, Phillips G, May L (2005). A tiered risk assessment approach to predicting diffuse agricultural phosphorus losses. Science of the Total Environment,, 344, 225-239.
Heathwaite AL, Dils RM, Liu S, Carvalho L, Brazier RE, Pope L, Hughes M, Phillips G, May L (2005). A tiered risk-based approach for predicting diffuse and point source phosphorus losses in agricultural areas.
Science of the Total Environment,
344(1-3 SPEC. ISS.), 225-239.
Abstract:
A tiered risk-based approach for predicting diffuse and point source phosphorus losses in agricultural areas
Implementation of the European Union Water Framework Directive requires an assessment of the pressures from human activity, which, combined with information on the sensitivity of the receiving waterbody to the pressures, will identify those water bodies at risk of failing to meet the Directive's environmental objectives. Part of the process of undertaking the risk assessment for lakes is an assessment of diffuse agricultural phosphorus (P) pressures. Three approaches of increasing sophistication were developed for this purpose: a basic 'risk screening' approach (tier 1) applicable to all lakes in Great Britain (GB) and based on export coefficients for different land cover classes and animal types; the Pressure Delivery Risk Screening Matrix approach (tier 2) that differentiated between pressures in surface water and groundwater river basins; and the Phosphorus Indicators Tool (PIT), a simple model of locational risk and P delivery potential (tier 3). Application of the three approaches to a range of lake catchments in England demonstrated that a tiered risk assessment approach was appropriate which was tailored to the quality of the available data. A step-wise procedure was developed whereby if the tier 1 and 2 approaches showed a catchment to be at high risk of failing to meet the Directive's environmental objectives with regard to P, it was justifiable to undertake a more detailed assessment using the tier 3 approach. The tier 1 approach was applied to all lakes in GB greater than 1 ha in size on the assumption that the boundary between the good/moderate status classes under the Water Framework Directive guidelines represented a doubling of the total P (TP) reference conditions. The initial outputs suggested that 51% of lakes in GB are predicted to not meet the TP targets identified for high or good status and must, therefore, be considered at risk. There were regional differences in numbers of lakes at risk. Scotland appeared to have the fewest sites at risk (18%); England the most (88%), with Wales having an intermediate percentage (56%). A comparison of P pressures on freshwaters using the tier 2 approach with other pressures on waterbodies (e.g. nitrate, sediment) in GB is shown as risk maps on the Environment Agency website at: www.environment-agency.gov.uk/wfdreview. The tier 3 approach was applied to data-rich catchments and identified at the 1 km2 areas of relatively high risk of P delivery to water. © 2005 Elsevier B.V. All rights reserved.
Abstract.
Liu S, Brazier R, Heathwaite L (2005). An investigation into the inputs controlling predictions from a diffuse phosphorus loss model for the UK; the Phosphorus Indicators Tool (PIT).
Science of the Total Environment,
344(1-3 SPEC. ISS.), 211-223.
Abstract:
An investigation into the inputs controlling predictions from a diffuse phosphorus loss model for the UK; the Phosphorus Indicators Tool (PIT)
A simple catchment scale model simulating diffuse phosphorus (P) loss from agricultural land to water, the Phosphorus Indicators Tool (PIT), has been developed. Previous research has shown that this model worked well in simulating the average annual P lost from two catchments: Windermere and Windrush, but it was not known which drivers in the model had the greatest control on predicted P delivery to water from agricultural land. In order to simulate the P export from each catchment source via each hydrological pathway specified individually, 108 coefficients are used in the model code. A univariate sensitivity analysis was conducted to evaluate which coefficient exerted the greatest control on the model output. Results from the univariate analysis suggest that the model is sensitive to a number of coefficients, but importantly, not all of the coefficients that were varied in the sensitivity analysis, altered the model output. The PIT model has been calibrated by optimizing results from the univariate analysis against observed data in the Windermere catchment. The simulated results from model calibration fit the observed data well, at the 95% level. This paper describes the methodology developed for the univariate analysis and evaluates the model calibration procedure against observed data from the Windermere catchment. © 2005 Elsevier B.V. All rights reserved.
Abstract.
Liu S, Brazier RE, Heathwaite AL (2005). An investigation into the inputs controlling predictions from the Phosphorus Indicators Tool (PIT). Science of the Total Environment, 344, 211-223.
Evans R, Brazier RE (2005). Evaluation of spatially distributed predictions of soil erosion by water versus field-based assessments. Environmental Science and Policy, 8, 493-501.
Beven KJ, Brazier RE, Heathwaite AL, Haygarth PM, Walling DE, Withers P (2005). On the concept of delivery of sediment and nutrients to stream channels. Hydrological Processes, 19, 551-556.
Brazier RE, Liu S, Heathwaite AL (2005). Scaling issues relating to P transfer from land to water. Journal of Hydrology, 304, 330-342.
Brazier RE, Parsons AJ, Powell DM, Kaduk J (2005). Streambed scour and fill in low-order dryland channels. Water Resources Research, 41(5).
2004
Parsons AJ, Wainwright J, Powell DM, Brazier RE (2004). A conceptual model for determining soil erosion by water. Earth Surface Processes and Landforms, 29, 1293-1302.
Brazier RE (2004). Quantifying soil erosion by water in the UK; a review of monitoring and modelling approaches. Progress in Physical Geography, 28(3), 1-26.
2003
Wainwright J, Parsons AJ, Powell DM, Brazier RE (2003). A new conceptual framework for understanding and predicting erosion by water from hillslopes and catchments. In II JCA, Flanagan DC (Eds.) Soil Erosion Research for the 21st Century, St Joseph, MI.: American Society of Agricultural Engineers, 607-610.
Powell DM, Brazier RE, Nichols M, Parsons AJ, Wainwright J (2003). Dynamics of scour and fill in ephemeral sand bed channels. In Renard, Kenneth G, McElroy, Stephen A, Gburek, William J, Canfield, Evan H, Scott, Russell L (Eds.) First Interagency Conference on Research in the Watersheds. U.S. Department of Agriculture, Agricultural Research Service, 134-140.
Wainwright J, Brazier RE, Parsons AJ, Michaelides K, Powell DM (2003). Linking short- and long-term soil-erosion modelling. In (Ed) Modelling Approaches for the Rhein LUCIFS Research Framework, Berlin.: Springer Verlag, Berlin.
2001
Brazier RE, Anthony SG, Quinn PF, Rowan JS (2001). "MIRSED" towards an MIR approach to modelling hillslope erosion at the national scale. CATENA, 42(1), 59-79.
Beven, K.J. Anthony, S.G. Rowan, J.S. (2001). Implications of model uncertainty for the mapping of hillslope-scale soil erosion predictions. Earth Surface Processes and Landforms, 26(12), 1333-1352.
2000
Brazier RE, Beven KJ, Freer J, Anthony SG, Rowan J (2000). Equifinality and Uncertainty in physically-based soil erosion models: application of the GLUE methodology to WEPP - the Water Erosion Prediction Project for sites in the UK and US. Earth Surface Processes and Landforms, 25, 825-845.
