Publications by year
In Press
Chadburn S, Burke E, Gallego-Sala A, Smith N (In Press). A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme.
Abstract:
A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme
<p>Representing peatlands in global Earth System Models (ESMs) is a major challenge, but a crucial one since peatlands represent a significant component of the global carbon cycle.</p><p>Here we present the first ESM implementation of peat accumulation and degradation that integrates both organic and mineral soils in a single formulation, implemented in JULES - the land-surface component of the UK Earth System Model (UKESM). In this scheme, the soil column is able to expand with the addition of new organic material and to subside as this material decomposes, with variable organic layer thickness, which means that peat can appear and disappear within the landscape without a need for a prescribed peatland fraction.</p><p>Thermal and hydraulic characteristics of the soil are dynamically updated depending on the organic matter content and its level of decomposition, using relationships derived from observations. This scheme captures important feedbacks within the soil, such as the way that peatlands - once formed - can be self-sustaining even under conditions where they would not form today. It also captures the loss of carbon and soil structure when peatlands are drained. We demonstrate this behaviour in the model.</p><p>This provides a new approach for improving the simulation of organic and peatland soils, and associated carbon-cycle feedbacks in ESMs.</p><p>The key remaining challenges for simulating global peatlands are to realistically distribute water around the landscape, in order to represent topographically-controlled peatlands, and to develop appropriate peatland vegetation types.</p>
Abstract.
Chadburn SE, Burke EJ, Gallego-Sala AV, Smith ND, Bret-Harte MS, Charman DJ, Drewer J, Edgar CW, Euskirchen ES, Fortuniak K, et al (In Press). A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme (JULES vn5.8_accumulate_soil).
Abstract:
A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme (JULES vn5.8_accumulate_soil)
Abstract. Peatlands have often been neglected in Earth System Models (ESMs). Where they are included, they are usually represented via a separate, prescribed grid cell fraction that is given the physical characteristics of a peat (highly organic) soil. However, in reality soils vary on a spectrum between purely mineral soil (no organic material), and purely organic soil, typically with an organic layer of variable thickness overlying mineral soil below. They are also dynamic, with organic layer thickness and its properties changing over time. Neither the spectrum of soil types nor their dynamic nature can be captured by current ESMs. Here we present a new version of an ESM land surface scheme (Joint UK Land Environment Simulator, JULES) where soil organic matter accumulation - and thus peatland formation, degradation and stability – is integrated in the vertically-resolved soil carbon scheme. We also introduce the capacity to track soil carbon age as a function of depth in JULES, and compare this to measured peat age-depth profiles. This scheme simulates dynamic feedbacks between the soil organic material and its thermal and hydraulic characteristics. We show that draining the peatlands can lead to significant carbon loss along with soil compaction and changes in peat properties. However, negative feedbacks can lead to the potential for peatlands to rewet themselves following drainage. These ecohydrological feedbacks can also lead to peatlands maintaining themselves in climates where peat formation would not otherwise initiate in the model, i.e. displaying some degree of resilience. The new model produces similar results to the original model for mineral soils, and realistic profiles of soil organic carbon for peatlands. In particular the best performing configurations had root mean squared error (RMSE) in carbon density for peat sites of 7.7–16.7 kgC m−3 depending on climate zone, when compared against typical peat profiles based on 216 sites from a global dataset of peat cores. This error is considerably smaller than the soil carbon itself (around 30–60 kgC m−3) and reduced by 35–80 % compared with standard JULES. The RMSE at mineral soil sites is also smaller in JULES-Peat than JULES itself (reduced by ~30–50 %). Thus JULES-Peat can be used as a complete scheme that simulates both organic and mineral soils. It does not require any additional input data and introduces minimal additional variables to the model. This provides a new approach for improving the simulation of organic and peatland soils, and associated carbon-cycle feedbacks in ESMs, which other land surface models could follow.
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Abstract.
Sim T, Swindles G, Morris P, Baird A, Cooper C, Gallego-Sala A, Charman D, Roland T, Borken W, Mullan D, et al (In Press). Divergent responses of permafrost peatlands to recent climate change.
Abstract:
Divergent responses of permafrost peatlands to recent climate change
<p>Permafrost peatlands are found in high-latitude regions and store globally-important amounts of soil organic carbon. These regions are warming at over twice the global average rate, causing permafrost thaw and exposing previously inert carbon to decomposition and emission to the atmosphere as greenhouse gases. However, it is unclear how peatland hydrological behaviour, vegetation structure and carbon balance, and the linkages between them, will respond to permafrost thaw in a warming climate. Here we show that permafrost peatlands follow divergent ecohydrological trajectories in response to recent climate change within the same rapidly warming region (northern Sweden). Whether a site becomes wetter or drier depends on local factors and the autogenic response of individual peatlands. We find that bryophyte-dominated vegetation demonstrates resistance, and in some cases resilience, to climatic and hydrological shifts. Drying at four sites is clearly associated with reduced carbon sequestration, while no clear relationship at wetting sites is observed. We highlight the complex dynamics of permafrost peatlands and warn against an overly-simple approach when considering their ecohydrological trajectories and role as C sinks under a warming climate.   </p>
Abstract.
Treat CC, Jones MC, Camill P, Gallego-Sala AV, Garneau M, Harden JW, Hugelius G, Klein ES, Kokfelt U, Kuhry P, et al (In Press). Effects of permafrost aggradation on peat properties as determined from a pan-arctic synthesis of plant macrofossils.
Journal of Geophysical Research Biogeosciences,
120Abstract:
Effects of permafrost aggradation on peat properties as determined from a pan-arctic synthesis of plant macrofossils
Permafrost dynamics play an important role in high-latitude peatland carbon balance and are key to understanding the future response of soil carbon stocks. Permafrost aggradation can control the magnitude of the carbon feedback in peatlands through effects on peat properties. We compiled peatland plant macrofossil records for the northern permafrost zone (515 cores from 280 sites) and classified samples by vegetation type and environmental class (fen, bog, tundra and boreal permafrost, thawed permafrost). We examined differences in peat properties (bulk density, carbon (C), nitrogen (N) and organic matter content, C/N ratio) and C accumulation rates among vegetation types and environmental classes. Consequences of permafrost aggradation differed between boreal and tundra biomes, including differences in vegetation composition, C/N ratios, and N content. The vegetation composition of tundra permafrost peatlands was similar to permafrost-free fens, while boreal permafrost peatlands more closely resembled permafrost-free bogs. Nitrogen content in boreal permafrost and thawed permafrost peatlands was significantly lower than in permafrost-free bogs despite similar vegetation types (0.9% versus 1.5% N). Median long-term C accumulation rates were higher in fens (23 g C m-2 y-1) than in permafrost-free bogs (18 g C m-2 y-1), and were lowest in boreal permafrost peatlands (14 g C m-2 y-1). The plant macrofossil record demonstrated transitions from fens to bogs to permafrost peatlands, bogs to fens, permafrost aggradation within fens, and permafrost thaw and re-aggradation. Using data synthesis, we've identified predominant peatland successional pathways, changes in vegetation type, peat properties, and C accumulation rates associated with permafrost aggradation.
Abstract.
Cooper CL, Swindles GT, Watson ET, Savov IP, Galka M, Gallego-Sala AV, Borken W (In Press). Evaluating tephrochronology in the permafrost peatlands of Northern Sweden. Quaternary Geochronology
Loisel J, Gallego-Sala A, Amesbury M, Roland T, Charman D (In Press). Expert assessment of future vulnerability of the global peatland carbon sink. Nature Climate Change
New SL, Belcher C, Hudspith VA, Gallego-Sala AV (In Press). Holocene fire history: can evidence of peat burning be found in the palaeo-archive?.
Mires and Peat,
18, 1-11.
Abstract:
Holocene fire history: can evidence of peat burning be found in the palaeo-archive?
Smouldering wildfires in peatlands have the potential to release substantial amounts of the carbon currently sequestered in these ecosystems. However, past studies of Holocene fire history in peatlands have given little consideration to the identification of evidence left behind after peat burning, or to charring of the peat matrix. In this study, modern peat samples from peatlands across the globe were charred in order to assess the identifiable characteristics of charred peat. On this basis we believe that charred aggregates of partially decayed organics which can be identified in cores provide clear evidence that the peat matrix itself burned. A range of
charred morphotypes could be found throughout a 2 m peat core from
and we are able to identify charred partially decayed aggregates that appeared to correspond with peaks in fire activity on the bog. These may reflect periods when surface fires ignited the peat surface below, or when the radiant heat from surface fires was sufficient to pyrolyse the surface peat. We conclude that it is possible to find evidence of peat burning in the palaeo-archive, and that future studies should begin to document the occurrence of charred particles so that the discipline can begin to build a picture of possible past peat fire
activity.
Abstract.
Ring-Hrubesh F, Welch B, Gallego-Sala A, Johnes P, Pancost R, Bryce C (In Press). Hydrological restoration of an upland peatland and its consequences for the microbial processing of dissolved organics.
Abstract:
Hydrological restoration of an upland peatland and its consequences for the microbial processing of dissolved organics
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<p>Peatland restoration efforts are accelerating globally with a primary aim of restoring the carbon balance of these ecosystems. Degraded peatlands export carbon to the atmosphere but also to freshwater environments as dissolved organic compounds. Whilst hydrological restoration measures can effectively reduce emissions of CO2 from upland peatlands, the impact on carbon export to the aquatic environment is less apparent. In some cases, dissolved organic concentrations can even increase after restoration, without clear mechanisms that could drive such a response. We aim to determine whether the response of the peat microbial community to restoration measures can explain poorly understood trends in dissolved organics. </p>
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<p>We investigated a severely degraded peatland in South Wales that has experienced historic drying to considerable depth, almost complete loss of surface vegetation, and a lowering of the peat surface. Restoration measures implemented over the past 16 years have involved hydrological intervention through gulley-blocking as well as efforts to stabilize the peat surface and re-establish plant communities.  Porewater collected over the first 6 months of our investigation indicates, contrary to expectation, that DOC concentrations were lowest in the most severely degraded region of the bog and highest in the least disturbed regions. We will discuss the potential drivers behind this observed trend, focusing on the role played by the peatland microbiome in the processing of dissolved organics in the peatland. In addition, we draw on water-table monitoring and sampling results to consider how environmental and geochemical conditions moderate biotic processing of dissolved organics. Improvement of our understanding of the microbial community response to rewetting measures is required as this underpins the function and carbon balance of these systems and will ultimately inform management approaches. </p>
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Abstract.
Naafs BDA, Inglis GN, Zheng Y, Amesbury MJ, Biester H, Bindler R, Blewett J, Burrows MA, del Castillo Torres D, Chambers FM, et al (In Press). Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids. Geochimica et Cosmochimica Acta
Zhang H, Amesbury M, Piilo S, Garneau M, Gallego-Sala A, Väliranta M (In Press). Recent changes in peatland testate amoeba functional traits and hydrology within a replicated site network in northwestern Québec, Canada. Frontiers in Ecology and Evolution, section Paleoecology
Piilo SR, Zhang H, Garneau M, Gallego-Sala AV, Amesbury M, Väliranta M (In Press). Recent peat and carbon accumulation following the Little Ice Age in northwestern Québec, Canada. Environmental Research Letters
Naafs BDA, Gallego-Sala AV, Inglis GN, Pancost RD (In Press). Refining the global branched glycerol dialkyl glycerol tetraether (brGDGT) soil temperature calibration. Organic Geochemistry
Davis TW, Prentice IC, Stocker BD, Whitely RJ, Wang H, Evans BJ, Gallego-Sala AV, Sykes MT, Cramer W (In Press). Simple Process-Led Algorithms for Simulating Habitats (SPLASH v.1.0): Robust Indices of Radiation, Evapotranspiration and Plant-Available Moisture.
Abstract:
Simple Process-Led Algorithms for Simulating Habitats (SPLASH v.1.0): Robust Indices of Radiation, Evapotranspiration and Plant-Available Moisture
Abstract. Bioclimatic indices for use in studies of ecosystem function, species distribution, and vegetation dynamics under changing climate scenarios depend on estimates of surface fluxes and other quantities, such as radiation, evapotranspiration and soil moisture, for which direct observations are sparse. These quantities can be derived indirectly from meteorological variables, such as air temperature, precipitation and cloudiness. Here we present a consolidated set of Simple Process-Led Algorithms for Simulating Habitats (SPLASH) allowing robust approximations of key quantities at ecologically relevant time scales. We specify equations, derivations, simplifications and assumptions for the estimation of daily and monthly quantities of top-of-the-atmosphere solar radiation, net surface radiation, photosynthetic photon flux density, evapotranspiration (potential, equilibrium and actual), condensation, soil moisture, and runoff, based on analysis of their relationship to fundamental climatic drivers. SPLASH, as presented here, is designed for application at discrete locations; however, the same methodology can naturally be applied to spatial grids. The climatic drivers include a minimum of three meteorological inputs: precipitation, air temperature, and either fraction of bright sunshine hours or fractional cloud cover. Indices, such as the moisture index, the climatic water deficit, and the Priestley-Taylor coefficient, are also defined. The SPLASH code is transcribed in C++, FORTRAN, Python, and R. One year of results from a specific location are provided to exemplify the daily and monthly model outputs, following a two-year spin-up of soil moisture content.
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Abstract.
Gallego-Sala AV, Charman DJ, Harrison SP, Li G, Prentice IC (In Press). Supplementary material to "Climate-driven expansion of blanket bogs in Britain during the Holocene".
Zhang H, Piilo S, Amesbury M, Charman D, Gallego-Sala AV, Väliranta M (In Press). The role of climate change in regulating Arctic permafrost peatland hydrological and vegetation change over the last millennium. Quaternary Science Reviews
Eberle A, Gallego-Sala A, Kappler A, Pancost RD, Bryce C (In Press). Variability of mineral protection of organic matter in thawing permafrost peatlands.
Abstract:
Variability of mineral protection of organic matter in thawing permafrost peatlands
<p>Permafrost preserves huge amounts of carbon in Arctic soils including peatlands, which are common in high latitudes. The potential for carbon release from these peatlands upon permafrost thaw is still a big uncertainty for climate predictions. Protection of organic matter against microbial degradation by association with minerals such as iron minerals has been identified as an important stabilization mechanism for organic carbon in soils [1]. In a permafrost peatland in northern Sweden (Stordalen mire) up to 20% of organic carbon was found associated with iron minerals in oxic peat layers [2]. However, upon thaw and collapse of frozen peat, reducing conditions cause microbial iron reduction and dissolution of minerals, therefore releasing associated carbon. Despite the prevalence of peatlands in the permafrost zone, little is known about the variability and overall importance of mineral protection in permafrost peatlands, and it is still uncertain how this will change upon collapse of palsas (frozen peat mounds). Following optimization of a protocol for Fe-OC quantification from peat, we sampled peat cores and pore water from different thawing palsas in the Torneträsk area of northern Sweden to quantify iron-carbon associations across different sites and estimate the changes in geochemistry upon permafrost thaw. Understanding these changes and differences between peatlands will help to predict the role of permafrost peatlands for carbon emissions triggered by permafrost thaw across larger geographical areas.</p><p>[1] Kaiser and Guggenberger (2000), Org. Geochem. 31, 711-725. [2] Patzner et al. (2020), Nat. Commun. 11, 6329.</p>
Abstract.
Bohn TJ, Melton JR, Ito A, Kleinen T, Spahni R, Stocker BD, Zhang B, Zhu X, Schroeder. R, Glagolev MV, et al (In Press). WETCHIMP-WSL: intercomparison of wetland methane emissions models over West Siberia.
Biogeosciences Discuss.,
12, 1907-1973.
Abstract:
WETCHIMP-WSL: intercomparison of wetland methane emissions models over West Siberia
Wetlands are the world's largest natural source of methane, a powerful greenhouse gas. The strong sensitivity of methane emissions to environmental factors such as soil temperature and moisture has led to concerns about potential positive feedbacks to climate change. This risk is particularly relevant at high latitudes, which have experienced pronounced warming and where thawing permafrost could potentially liberate large amounts of labile carbon over the next 100 years. However, global models disagree as to the magnitude and spatial distribution of emissions, due to uncertainties in wetland area and emissions per unit area and a scarcity of in situ observations. Recent intensive field campaigns across the West Siberian Lowland (WSL) make this an ideal region over which to assess the performance of large-scale process-based wetland models in a high-latitude environment. Here we present the results of a follow-up to the Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP), focused on the West Siberian Lowland (WETCHIMP-WSL). We assessed 21 models and 5 inversions over this domain in terms of total CH4 emissions, simulated wetland areas, and CH4 fluxes per unit wetland area and compared these results to an intensive in situ CH4 flux dataset, several wetland maps, and two satellite inundation products. We found that: (a) despite the large scatter of individual estimates, 12 year mean estimates of annual total emissions over the WSL from forward models (5.34 ± 0.54 Tg CH4 y-1), inversions (6.06 ± 1.22 Tg CH4 y-1), and in situ observations (3.91 ± 1.29 Tg CH4 y-1) largely agreed, (b) forward models using inundation products alone to estimate wetland areas suffered from severe biases in CH4 emissions, (c) the interannual timeseries of models that lacked either soil thermal physics appropriate to the high latitudes or realistic emissions from unsaturated peatlands tended to be dominated by a single environmental driver (inundation or air temperature), unlike those of inversions and more sophisticated forward models, (d) differences in biogeochemical schemes across models had relatively smaller influence over performance; and (e) multi-year or multi-decade observational records are crucial for evaluating models' responses to long-term climate change.
Abstract.
2023
Robinson CH, Ritson JP, Alderson DM, Malik AA, Griffiths RI, Heinemeyer A, Gallego-Sala AV, Quillet A, Robroek BJM, Evans C, et al (2023). Aspects of microbial communities in peatland carbon cycling under changing climate and land use pressures.
Mires and Peat,
29Abstract:
Aspects of microbial communities in peatland carbon cycling under changing climate and land use pressures
Globally, major efforts are being made to restore peatlands to maximise their resilience to anthropogenic climate change, which puts continuous pressure on peatland ecosystems and modifies the geography of the environmental envelope that underpins peatland functioning. A probable effect of climate change is reduction in the waterlogged conditions that are key to peatland formation and continued accumulation of carbon (C) in peat. C sequestration in peatlands arises from a delicate imbalance between primary production and decomposition, and microbial processes are potentially pivotal in regulating feedbacks between environmental change and the peatland C cycle. Increased soil temperature, caused by climate warming or disturbance of the natural vegetation cover and drainage, may result in reductions of long-term C storage via changes in microbial community composition and metabolic rates. Moreover, changes in water table depth alter the redox state and hence have broad consequences for microbial functions, including effects on fungal and bacterial communities especially methanogens and methanotrophs. This article is a perspective review of the effects of climate change and ecosystem restoration on peatland microbial communities and the implications for C sequestration and climate regulation. It is authored by peatland scientists, microbial ecologists, land managers and non-governmental organisations who were attendees at a series of three workshops held at the University of Manchester (UK) in 2019–2020. Our review suggests that the increase in methane flux sometimes observed when water tables are restored is predicated on the availability of labile carbon from vegetation and the absence of alternative terminal electron acceptors. Peatland microbial communities respond relatively rapidly to shifts in vegetation induced by climate change and subsequent changes in the quantity and quality of below-ground C substrate inputs. Other consequences of climate change that affect peatland microbial communities and C cycling include alterations in snow cover and permafrost thaw. In the face of rapid climate change, restoration of a resilient microbiome is essential to sustaining the climate regulation functions of peatland systems. Technological developments enabling faster characterisation of microbial communities and functions support progress towards this goal, which will require a strongly interdisciplinary approach.
Abstract.
Murguia‐Flores F, Jaramillo VJ, Gallego‐Sala A (2023). Assessing Methane Emissions from Tropical Wetlands: Uncertainties from Natural Variability and Drivers at the Global Scale.
Global Biogeochemical Cycles,
37(9).
Abstract:
Assessing Methane Emissions from Tropical Wetlands: Uncertainties from Natural Variability and Drivers at the Global Scale
AbstractMethane (CH4) emissions from tropical wetlands represent half of the global wetland emissions, but uncertainties remain concerning the extent of tropical methane sources. One limitation is to conceive tropical wetlands as a single ecosystem, especially in global land surface models. We estimate CH4 emissions and assess their environmental and anthropogenic drivers. We created a data set with 101 studies involving 328‐point measurements, classified the sites into four wetland types, and included relevant biological and environmental information. We estimate the global CH4 emission rate from tropical wetlands as 35 (5–160) mg CH4 m−2 d−1 (median, first and third quartile) and an annual global rate of 94 (56, 158) Tg y−1. Fluxes differed among the wetland types, but except for anthropogenic factors, significant environmental drivers at the global scale could not be quantitatively identified because of high flux variability, even within wetland types. Coastal wetlands generate median emissions of 12 (5–23) Tg y−1. Inland deep‐water wetlands emit 53 (32–114) Tg y−1, with highly variable areal extent. Emissions from inland shallow‐water wetlands are 52 (33–78) Tg y−1 with variation due to seasonal changes in water table level. Human‐made wetlands emit 17 (10−4) Tg y−1. Pollution and N inputs from agriculture are significant anthropogenic drivers of emissions from tropical wetlands. Specific drivers of change need to be considered according to wetland type when estimating global emissions as well as their specific vulnerability to global change. Additionally, these differences should be considered when implementing wetland management practices aimed at decreasing methane emissions.
Abstract.
Juselius T, Ravolainen V, Zhang H, Piilo S, Müller M, Gallego-Sala A, Väliranta M (2023). Author Correction: Newly initiated carbon stock, organic soil accumulation patterns and main driving factors in the High Arctic Svalbard, Norway.
Sci Rep,
13(1).
Author URL.
Piilo SR, Väliranta MM, Amesbury MJ, Aquino-López MA, Charman DJ, Gallego-Sala A, Garneau M, Koroleva N, Kärppä M, Laine AM, et al (2023). Consistent centennial-scale change in European sub-Arctic peatland vegetation toward Sphagnum dominance-Implications for carbon sink capacity.
Glob Chang Biol,
29(6), 1530-1544.
Abstract:
Consistent centennial-scale change in European sub-Arctic peatland vegetation toward Sphagnum dominance-Implications for carbon sink capacity.
Climate warming is leading to permafrost thaw in northern peatlands, and current predictions suggest that thawing will drive greater surface wetness and an increase in methane emissions. Hydrology largely drives peatland vegetation composition, which is a key element in peatland functioning and thus in carbon dynamics. These processes are expected to change. Peatland carbon accumulation is determined by the balance between plant production and peat decomposition. But both processes are expected to accelerate in northern peatlands due to warming, leading to uncertainty in future peatland carbon budgets. Here, we compile a dataset of vegetation changes and apparent carbon accumulation data reconstructed from 33 peat cores collected from 16 sub-arctic peatlands in Fennoscandia and European Russia. The data cover the past two millennia that has undergone prominent changes in climate and a notable increase in annual temperatures toward present times. We show a pattern where European sub-Arctic peatland microhabitats have undergone a habitat change where currently drier habitats dominated by Sphagnum mosses replaced wetter sedge-dominated vegetation and these new habitats have remained relatively stable over the recent decades. Our results suggest an alternative future pathway where sub-arctic peatlands may at least partly sustain dry vegetation and enhance the carbon sink capacity of northern peatlands.
Abstract.
Author URL.
Ramdzan KNM, Moss P, Jacobsen G, Gallego-Sala A, Charman D, Harrison ME, Page S, Mishra S, Wardle DA, Jaya A, et al (2023). Insights for Restoration: Reconstructing the Long-Term Responses and Resilience of Vegetation, Hydrology and Peat Conditions to Fire Events in a Tropical Peatland in Central Kalimantan.
Ramdzan KNM, Moss PT, Jacobsen G, Gallego-Sala A, Charman D, Harrison ME, Page S, Mishra S, Wardle DA, Jaya A, et al (2023). Insights for restoration: Reconstructing the drivers of long-term local fire events and vegetation turnover of a tropical peatland in Central Kalimantan. Palaeogeography Palaeoclimatology Palaeoecology, 628
Sim TG, Swindles GT, Morris PJ, Baird AJ, Gallego-Sala AV, Wang Y, Blaauw M, Camill P, Garneau M, Hardiman M, et al (2023). Regional variability in peatland burning at mid-to high-latitudes during the Holocene. Quaternary Science Reviews, 305, 108020-108020.
Frieler K, Volkholz J, Lange S, Schewe J, Mengel M, del Rocío Rivas López M, Otto C, Reyer CPO, Karger DN, Malle JT, et al (2023). Scenario set-up and forcing data for impact model evaluation and impact attribution within the third round of the Inter-Sectoral Model Intercomparison Project (ISIMIP3a). , 2023, 1-83.
Pancost R, Blewett J, Naafs D, Vreeken M, Gallego-Sala A, Pearson A, Schubotz F (2023). The Tropical Peatland Archaeal Lipidome – Influence of Vegetation and Redox on Diversity. IMOG 2023.
Sun J, Gallego-Sala A, Yu Z (2023). Topographic and climatic controls of peatland distribution on the Tibetan Plateau.
Scientific Reports,
13(1).
Abstract:
Topographic and climatic controls of peatland distribution on the Tibetan Plateau
The Tibetan Plateau (TP) hosts a variety of mountain peatlands that are sensitive to the amplified warming in this region. However, we still lack a basic understanding of environmental and climatic factors controlling peatland distribution in the region. Here we use a bioclimatic envelope model (PeatStash) and environmental analysis that utilise three peatland datasets—(a) the well-studied Zoige peatland complex, (b) a literature-based dataset of TP peatlands sites, and (c) an existing global peatland map (PEATMAP)—to investigate major drivers of peatland distribution in the TP. The Zoige peatland complex is defined by gentle slopes (< 2°), mean annual temperature at 0–2 °C, and soil moisture index > 1.7, much narrower thresholds than those stemming from PEATMAP. Using these narrower thresholds to predict future changes, we found that the Zoige peatland complex will shrink greatly under full-range future warming scenarios (both SSP1–2.6 and SSP5–8.5). Modelling peatland distribution in the entire TP remains challenging because accurate environmental and climate data at high resolution and a reliable peatland distribution map are still lacking. Improved peatland mapping supported by ground-truthing is necessary to understand drivers of peatland distribution, assess carbon storage and other ecosystem services, and predict the TP’s peatlands fate under climate change.
Abstract.
Vreeken M, Blewett J, Smit NT, Schubotz F, Gallego-Sala A, Naafs D, Pancost R (2023). Tropical Peatland Biogeochemistry Along an Ecological Transect: the Enigmatic Fate of Organic Matter. IMOG 2023.
2022
Chadburn SE, Burke EJ, Gallego-Sala AV, Smith ND, Bret-Harte MS, Charman DJ, Drewer J, Edgar CW, Euskirchen ES, Fortuniak K, et al (2022). A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme (JULES vn5.8_accumulate_soil) for northern and temperate peatlands.
Geoscientific Model Development,
15(4), 1633-1657.
Abstract:
A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme (JULES vn5.8_accumulate_soil) for northern and temperate peatlands
Abstract. Peatlands have often been neglected in Earth system models (ESMs). Where they are included, they are usually represented via a separate, prescribed grid cell fraction that is given the physical characteristics of a peat (highly organic) soil. However, in reality soils vary on a spectrum between purely mineral soil (no organic material) and purely organic soil, typically with an organic layer of variable thickness overlying mineral soil below. They are also dynamic, with organic layer thickness and its properties changing over time. Neither the spectrum of soil types nor their dynamic nature can be captured by current ESMs. Here we present a new version of an ESM land surface scheme (Joint UK Land Environment Simulator, JULES) where soil organic matter accumulation – and thus peatland formation, degradation and stability – is integrated in the vertically resolved soil carbon scheme. We also introduce the capacity to track soil carbon age as a function of depth in JULES and compare this to measured peat age–depth profiles. The new scheme is tested and evaluated at northern and temperate sites. This scheme simulates dynamic feedbacks between the soil organic material and its thermal and hydraulic characteristics. We show that draining the peatlands can lead to significant carbon loss, soil compaction and changes in peat properties. However, negative feedbacks can lead to the potential for peatlands to rewet themselves following drainage. These ecohydrological feedbacks can also lead to peatlands maintaining themselves in climates where peat formation would not otherwise initiate in the model, i.e. displaying some degree of resilience. The new model produces similar results to the original model for mineral soils and realistic profiles of soil organic carbon for peatlands. We evaluate the model against typical peat profiles based on 216 northern and temperate sites from a global dataset of peat cores. The root-mean-squared error (RMSE) in the soil carbon profile is reduced by 35 %–80 % in the best-performing JULES-Peat simulations compared with the standard JULES configuration. The RMSE in these JULES-Peat simulations is 7.7–16.7 kg C m−3 depending on climate zone, which is considerably smaller than the soil carbon itself (around 30–60 kg C m−3). The RMSE at mineral soil sites is also reduced in JULES-Peat compared with the original JULES configuration (reduced by ∼ 30 %–50 %). Thus, JULES-Peat can be used as a complete scheme that simulates both organic and mineral soils. It does not require any additional input data and introduces minimal additional variables to the model. This provides a new approach for improving the simulation of organic and peatland soils and associated carbon-cycle feedbacks in ESMs.
Abstract.
Qiu C, Ciais P, Zhu D, Guenet B, Chang J, Chaudhary N, Kleinen T, Li XY, Müller J, Xi Y, et al (2022). A strong mitigation scenario maintains climate neutrality of northern peatlands.
One Earth,
5(1), 86-97.
Abstract:
A strong mitigation scenario maintains climate neutrality of northern peatlands
Northern peatlands store 300–600 Pg C, of which approximately half are underlain by permafrost. Climate warming and, in some regions, soil drying from enhanced evaporation are progressively threatening this large carbon stock. Here, we assess future CO2 and CH4 fluxes from northern peatlands using five land surface models that explicitly include representation of peatland processes. Under Representative Concentration Pathways (RCP) 2.6, northern peatlands are projected to remain a net sink of CO2 and climate neutral for the next three centuries. A shift to a net CO2 source and a substantial increase in CH4 emissions are projected under RCP8.5, which could exacerbate global warming by 0.21°C (range, 0.09–0.49°C) by the year 2300. The true warming impact of peatlands might be higher owing to processes not simulated by the models and direct anthropogenic disturbance. Our study highlights the importance of understanding how future warming might trigger high carbon losses from northern peatlands.
Abstract.
Loisel J, Gallego-Sala A (2022). Ecological resilience of restored peatlands to climate change.
COMMUNICATIONS EARTH & ENVIRONMENT,
3(1).
Author URL.
Gałka M, Knorr K-H, Tobolski K, Gallego-Sala A, Kołaczek P, Lamentowicz M, Kajukało-Drygalska K, Marcisz K (2022). How far from a pristine state are the peatlands in the Białowieża Primeval Forest (CE Europe) – Palaeoecological insights on peatland and forest development from multi-proxy studies. Ecological Indicators, 143
Blewett J, Elling FJ, Naafs BDA, Kattein L, Evans TW, Lauretano V, Gallego-Sala AV, Pancost RD, Pearson A (2022). Metabolic and ecological controls on the stable carbon isotopic composition of archaeal (isoGDGT and BDGT) and bacterial (brGDGT) lipids in wetlands and lignites. Geochimica et Cosmochimica Acta, 320, 1-25.
Juselius T, Ravolainen V, Zhang H, Piilo S, Muller M, Gallego-Sala A, Valiranta M (2022). Newly initiated carbon stock, organic soil accumulation patterns and main driving factors in the High Arctic Svalbard, Norway.
SCIENTIFIC REPORTS,
12(1).
Author URL.
Crichton KA, Anderson K, Charman DJ, Gallego-Sala A (2022). Seasonal climate drivers of peak NDVI in a series of Arctic peatlands.
Sci Total Environ,
838(Pt 3).
Abstract:
Seasonal climate drivers of peak NDVI in a series of Arctic peatlands.
Changes in plant cover and productivity are important in driving Arctic soil carbon dynamics and sequestration, especially in peatlands. Warming trends in the Arctic are known to have resulted in changes in plant productivity, extent and community composition, but more data are still needed to improve understanding of the complex controls and processes involved. Here we assess plant productivity response to climate variability between 1985 and 2020 by comparing peak growing season NDVI (Normalised Difference Vegetation Index data from Landsat 5 and 7), to seasonal-average weather data (temperature, precipitation and snow-melt timing) in nine locations containing peatlands in high- and low-Arctic regions in Europe and Canada. We find that spring (correlation 0.36 for peat dominant and 0.39 for mosaic; MLR coefficient 0.20 for peat, 0.29 for mosaic), summer (0.47, 0.42; 0.18, 0.17) and preceding-autumn (0.35, 0.25; 0.33, 0.27) temperature are linked to peak growing season NDVI at our sites between 1985 and 2020, whilst spring snow melt timing (0.42, 0.45; 0.25, 0.32) is also important, and growing season water availability is likely site-specific. According to regression trees, a warm preceding autumn (September-October-November) is more important than a warm summer (June-July-August) in predicting the highest peak season productivity in the peat-dominated areas. Mechanisms linked to soil processes may explain the importance of previous-Autumn conditions on productivity. We further find that peak productivity increases in these Arctic peatlands are comparable to those in the surrounding non-peatland-dominant vegetation. Increased productivity in and around Arctic peatlands suggests a potential to increased soil carbon sequestration with future warming, but further work is needed to test whether this is evident in observations of recent peat accumulation and extent.
Abstract.
Author URL.
2021
Young DM, Baird AJ, Gallego-Sala AV, Loisel J (2021). A cautionary tale about using the apparent carbon accumulation rate (aCAR) obtained from peat cores.
Scientific Reports,
11(1).
Abstract:
A cautionary tale about using the apparent carbon accumulation rate (aCAR) obtained from peat cores
The carbon (C) accumulation histories of peatlands are of great interest to scientists, land users and policy makers. Because peatlands contain more than 500 billion tonnes of C, an understanding of the fate of this dynamic store, when subjected to the pressures of land use or climate change, is an important part of climate-change mitigation strategies. Information from peat cores is often used to recreate a peatland’s C accumulation history from recent decades to past millennia, so that comparisons between past and current rates can be made. However, these present day observations of peatlands’ past C accumulation rates (known as the apparent rate of C accumulation - aCAR) are usually different from the actual uptake or loss of C that occurred at the time (the true C balance). Here we use a simple peatland model and a more detailed ecosystem model to illustrate why aCAR should not be used to compare past and current C accumulation rates. Instead, we propose that data from peat cores are used with existing or new C balance models to produce reliable estimates of how peatland C function has changed over time.
Abstract.
Loisel J, Gallego-Sala AV, Amesbury MJ, Magnan G, Anshari G, Beilman DW, Benavides JC, Blewett J, Camill P, Charman DJ, et al (2021). Author Correction: Expert assessment of future vulnerability of the global peatland carbon sink. Nature Climate Change, 11(4), 362-362.
Alex Whittle, Robert L. Barnett, Dan J. Charman, Angela V. Gallego‐Sala (2021). Author response for "Low‐salinity transitions drive abrupt microbial response to sea‐level change".
Alex Whittle, Robert L. Barnett, Dan J. Charman, Angela V. Gallego‐Sala (2021). Author response for "Low‐salinity transitions drive abrupt microbial response to sea‐level change".
Sim TG, Swindles GT, Morris PJ, Baird AJ, Cooper CL, Gallego-Sala AV, Charman DJ, Roland TP, Borken W, Mullan DJ, et al (2021). Divergent responses of permafrost peatlands to recent climate change.
Environmental Research Letters,
16(3), 034001-034001.
Abstract:
Divergent responses of permafrost peatlands to recent climate change
Abstract
. Permafrost peatlands are found in high-latitude regions and store globally-important amounts of soil organic carbon. These regions are warming at over twice the global average rate, causing permafrost thaw, and exposing previously inert carbon to decomposition and emission to the atmosphere as greenhouse gases. However, it is unclear how peatland hydrological behaviour, vegetation structure and carbon balance, and the linkages between them, will respond to permafrost thaw in a warming climate. Here we show that permafrost peatlands follow divergent ecohydrological trajectories in response to recent climate change within the same rapidly warming region (northern Sweden). Whether a site becomes wetter or drier depends on local factors and the autogenic response of individual peatlands. We find that bryophyte-dominated vegetation demonstrates resistance, and in some cases resilience, to climatic and hydrological shifts. Drying at four sites is clearly associated with reduced carbon sequestration, while no clear relationship at wetting sites is observed. We highlight the complex dynamics of permafrost peatlands and warn against an overly-simple approach when considering their ecohydrological trajectories and role as C sinks under a warming climate.
Abstract.
Sim TG, Swindles GT, Morris PJ, Baird AJ, Charman DJ, Amesbury MJ, Beilman D, Channon A, Gallego-Sala AV (2021). Ecology of peatland testate amoebae in Svalbard and the development of transfer functions for reconstructing past water-table depth and pH.
Ecological Indicators,
131Abstract:
Ecology of peatland testate amoebae in Svalbard and the development of transfer functions for reconstructing past water-table depth and pH
Peatlands are valuable archives of information about past environmental conditions and represent a globally-important carbon store. Robust proxy methods are required to reconstruct past ecohydrological dynamics in high-latitude peatlands to improve our understanding of change in these carbon-rich ecosystems. The High Arctic peatlands in Svalbard are at the northern limit of current peatland distribution and have experienced rapidly rising temperatures of 0.81 °C per decade since 1958. We examine the ecology of peatland testate amoebae in surface vegetation samples from permafrost peatlands on Spitsbergen, the largest island of the Svalbard archipelago, and develop new transfer functions to reconstruct water-table depth (WTD) and pH that can be applied to understand past peatland ecosystem dynamics in response to climate change. These transfer functions are the first of their kind for peatlands in Svalbard and the northernmost developed to date. Multivariate statistical analysis shows that WTD and pore water pH are the dominant controls on testate amoeba species distribution. This finding is consistent with results from peatlands in lower latitudes with regard to WTD and supports work showing that when samples are taken across a long enough trophic gradient, peatland trophic status is an important control on the distribution of testate amoebae. No differences were found between transfer functions including and excluding the taxa with weak idiosomic tests (WISTs) that are most susceptible to decay. The final models for application to fossil samples therefore excluded these taxa. The WTD transfer function demonstrates the best performance (R2LOO = 0.719, RMSEPLOO = 3.2 cm), but the pH transfer function also performs well (R2LOO = 0.690, RMSEPLOO = 0.320). The transfer functions were applied to a core from western Spitsbergen and suggest drying conditions ~1750 CE, followed by a trend of recent wetting and increasing pH from ~1920 CE. These new transfer functions allow the reconstruction of past peatland WTD and pH in Svalbard, thereby enabling a greater understanding of long-term ecohydrological dynamics in these rapidly changing ecosystems.
Abstract.
Eberle A, Patzner M, Byrne J, Bryce C, Kappler A, Pancost R, Gallego-Sala A (2021). Improving quantification of iron-associated organic carbon in organic-rich soils. Goldschmidt2021 abstracts.
Qiu C, Ciais P, Zhu D, Guenet B, Peng S, Petrescu AMR, Lauerwald R, Makowski D, Gallego-Sala AV, Charman DJ, et al (2021). Large historical carbon emissions from cultivated northern peatlands.
Science Advances,
7(23).
Abstract:
Large historical carbon emissions from cultivated northern peatlands
. Crop cultivation of northern peatlands emitted large amount of CO
. 2
. over the period 850–2010.
.
Abstract.
Whittle A (2021). Late Quaternary changes in the Westerly Winds over the Southern Ocean.
Abstract:
Late Quaternary changes in the Westerly Winds over the Southern Ocean
The latitudinal position and intensity of the Southern Hemisphere westerly winds (SHW) has important and far-reaching implications for global climate and the physical environment in the southern high latitudes. Despite this, our ability to project how they will change in the future is reduced by limited understanding of their behaviour over centennial to millennial timescales. Peatland archives on the sub-Antarctic Islands are uniquely located inside the core wind-belt (50-55˚S), and hence ideally situated to reconstruct changes in westerly wind behaviour. However, suitable proxies to develop reconstructions of wind-strength throughout the region are lacking. Westerly winds are shown to enrich the sub-Antarctic Islands with salt-spray in concentrations that are proportional to wind-strength. This research has tested the potential for peat-dwelling testate amoebae to act as a bioindicator for variations in salt-spray deposition through time. Measurements of communities in variably salt-enriched environments - spanning a gradient from predominantly freshwater to salt-marsh - revealed a strong relationship between the productivity of testate amoeba communities and salinity, which allows past salt-concentrations to be inferred from sub-fossil assemblages. Presented here are two reconstructions of SHW intensity over the South Atlantic, based primarily on changes in the productivity of testate amoeba communities. The first provides a high-resolution record of the changes in wind-intensity over recent decades, extending beyond the observational record to 1920 CE, and demonstrating that present-day wind conditions are unprecedented over the last century. The second record, collected from the same site, provides a c. 8000-year reconstruction of wind-intensity over the South Atlantic, based on changes in testate amoeba productivity as part of a multi-proxy analysis that includes three independent proxies to track the deposition of salt-spray aerosols and minerogenic particles into the peat record on Bird Island (sub-Antarctica). Three significant phases of intensified winds during this period (0.45-1.15, 2.8-3.65 and 4.45-8 k yr BP) indicate long-term correspondence between temperature and wind-strength at 54˚S. These observations suggest that with climatic warming in the 21st Century, the westerly wind belt will continue to intensify and displace southwards, leading to increased wind-stress over the Southern Ocean. Implications of this shift are expected to include; reduced precipitation supply to the Southern Hemisphere continents, reduced Antarctic ice-sheet stability and increased contributions to global sea-level, and weakening of the Southern Ocean carbon sink, allowing accumulation of more CO₂ in the atmosphere.
Abstract.
Whittle A, Barnett RL, Charman DJ, Gallego‐Sala AV (2021). Low‐salinity transitions drive abrupt microbial response to sea‐level change.
Ecology Letters,
25(1), 17-25.
Abstract:
Low‐salinity transitions drive abrupt microbial response to sea‐level change
AbstractThe salinisation of many coastal ecosystems is underway and is expected to continue into the future because of sea‐level rise and storm intensification brought about by the changing climate. However, the response of soil microbes to increasing salinity conditions within coastal environments is poorly understood, despite their importance for nutrient cascading, carbon sequestration and wider ecosystem functioning. Here, we demonstrate deterioration in the productivity of a top‐tier microbial group (testate amoebae) with increasing coastal salinity, which we show to be consistent across phylogenetic groups, salinity gradients, environment types and latitude. Our results show that microbial changes occur in the very early stages of marine inundation, presaging more radical changes in soil and ecosystem function and providing an early warning of coastal salinisation that could be used to improve coastal planning and adaptation.
Abstract.
Ritson JP, Alderson DM, Robinson CH, Burkitt AE, Heinemeyer A, Stimson AG, Gallego-Sala A, Harris A, Quillet A, Malik AA, et al (2021). Towards a microbial process-based understanding of the resilience of peatland ecosystem service provisioning - a research agenda.
Sci Total Environ,
759Abstract:
Towards a microbial process-based understanding of the resilience of peatland ecosystem service provisioning - a research agenda.
Peatlands are wetland ecosystems with great significance as natural habitats and as major global carbon stores. They have been subject to widespread exploitation and degradation with resulting losses in characteristic biota and ecosystem functions such as climate regulation. More recently, large-scale programmes have been established to restore peatland ecosystems and the various services they provide to society. Despite significant progress in peatland science and restoration practice, we lack a process-based understanding of how soil microbiota influence peatland functioning and mediate the resilience and recovery of ecosystem services, to perturbations associated with land use and climate change. We argue that there is a need to: in the short-term, characterise peatland microbial communities across a range of spatial and temporal scales and develop an improved understanding of the links between peatland habitat, ecological functions and microbial processes; in the medium term, define what a successfully restored 'target' peatland microbiome looks like for key carbon cycle related ecosystem services and develop microbial-based monitoring tools for assessing restoration needs; and in the longer term, to use this knowledge to influence restoration practices and assess progress on the trajectory towards 'intact' peatland status. Rapid advances in genetic characterisation of the structure and functions of microbial communities offer the potential for transformative progress in these areas, but the scale and speed of methodological and conceptual advances in studying ecosystem functions is a challenge for peatland scientists. Advances in this area require multidisciplinary collaborations between peatland scientists, data scientists and microbiologists and ultimately, collaboration with the modelling community. Developing a process-based understanding of the resilience and recovery of peatlands to perturbations, such as climate extremes, fires, and drainage, will be key to meeting climate targets and delivering ecosystem services cost effectively.
Abstract.
Author URL.
2020
Lewis K, Rumpang E, Kho LK, McCalmont J, Teh YA, Gallego-Sala A, Hill TC (2020). An assessment of oil palm plantation aboveground biomass stocks on tropical peat using destructive and non-destructive methods.
Scientific Reports,
10(1).
Abstract:
An assessment of oil palm plantation aboveground biomass stocks on tropical peat using destructive and non-destructive methods
The recent expansion of oil palm (OP, Elaeis guineensis) plantations into tropical forest peatlands has resulted in ecosystem carbon emissions. However, estimates of net carbon flux from biomass changes require accurate estimates of the above ground biomass (AGB) accumulation rate of OP on peat. We quantify the AGB stocks of an OP plantation on drained peat in Malaysia from 3 to 12 years after planting using destructive harvests supported by non-destructive surveys of a further 902 palms. Peat specific allometric equations for palm (R2 = 0.92) and frond biomass are developed and contrasted to existing allometries for OP on mineral soils. Allometries are used to upscale AGB estimates to the plantation block-level. Aboveground biomass stocks on peat accumulated at ~6.39 ± 1.12 Mg ha−1 per year in the first 12 years after planting, increasing to ~7.99 ± 0.95 Mg ha−1 yr−1 when a ‘perfect’ plantation was modelled. High inter-palm and inter-block AGB variability was observed in mature classes as a result of variations in palm leaning and mortality. Validation of the allometries defined and expansion of non-destructive inventories across alternative plantations and age classes on peat would further strengthen our understanding of peat OP AGB accumulation rates.
Abstract.
Blewett J, Naafs BDA, Gallego-Sala AV, Pancost RD (2020). Effects of temperature and pH on archaeal membrane lipid distributions in freshwater wetlands. Organic Geochemistry, 148, 104080-104080.
Ritchie P, Smith G, Davis K, Fezzi C, Halleck-Vega S, Harper A, Boulton C, Binner A, Day B, Gallego-Sala A, et al (2020). Shifts in national land use and food production in Great Britain after a climate tipping point. Nature Food, 1, 76-83.
2019
Blewett J, Naafs BDA, Gallego-Sala AV, Pancost RD (2019). A novel proxy based on archaeal lipids for tropical terrestrial temperatures in ancient greenhouse climates.
Blewett J, Naafs BDA, Gallego-Sala AV, Pancost RD (2019). A novel proxy based on archaeal lipids for tropical terrestrial temperatures in ancient greenhouse climates.
Blewett J, Naafs BDA, Gallego-Sala AV, Pancost RD (2019). A novel proxy based on archaeal lipids for tropical terrestrial temperatures in ancient greenhouse climates.
Martínez Cortizas A, López-Costas O, Orme L, Mighall T, Kylander ME, Bindler R, Gallego Sala Á (2019). Holocene atmospheric dust deposition in NW Spain.
The Holocene,
30(4), 507-518.
Abstract:
Holocene atmospheric dust deposition in NW Spain
Atmospheric dust plays an important role in terrestrial and marine ecosystems, particularly those that are nutrient limited. Despite that most dust originates from arid and semi-arid regions, recent research has shown that past dust events may have been involved in boosting productivity in nutrient-poor peatlands. We investigated dust deposition in a mid-latitude, raised bog, which is surrounded by a complex geology (paragneiss/schist, granite, quartzite and granodiorite). As proxies for dust fluxes, we used accumulation rates of trace (Ti, Zr, Rb, Sr and Y) as well as major (K and Ca) lithogenic elements. The oldest, largest dust deposition event occurred between ~8.6 and ~7.4 ka BP, peaking at ~8.1 ka BP (most probably the 8.2 ka BP event). The event had a large impact on the evolution of the mire, which subsequently transitioned from a fen into a raised bog in ~1500 years. From ~6.7 to ~4.0 ka BP, fluxes were very low, coeval with mid-Holocene forest stability and maximum extent. In the late Holocene, after ~4.0 ka BP, dust events became more prevalent with relatively major deposition at ~3.2–2.5, ~1.4 ka BP and ~0.35–0.05 ka BP, and minor peaks at ~4.0–3.7, ~1.7, ~1.10–0.95 ka BP and ~0.74–0.58 ka BP. Strontium fluxes display a similar pattern between ~11 and ~6.7 ka BP but then became decoupled from the other elements from the mid Holocene onwards. This seems to be a specific signal of the granodiorite batholith, which has an Sr anomaly. The reconstructed variations in dust fluxes bear a strong climatic imprint, probably related to storminess controlled by North Atlantic Oscillation conditions. Complex interactions also arise because of increased pressure from human activities.
Abstract.
Young DM, Baird AJ, Charman DJ, Evans CD, Gallego-Sala AV, Gill PJ, Hughes PDM, Morris PJ, Swindles GT (2019). Misinterpreting carbon accumulation rates in records from near-surface peat.
Sci Rep,
9(1).
Abstract:
Misinterpreting carbon accumulation rates in records from near-surface peat.
Peatlands are globally important stores of carbon (C) that contain a record of how their rates of C accumulation have changed over time. Recently, near-surface peat has been used to assess the effect of current land use practices on C accumulation rates in peatlands. However, the notion that accumulation rates in recently formed peat can be compared to those from older, deeper, peat is mistaken - continued decomposition means that the majority of newly added material will not become part of the long-term C store. Palaeoecologists have known for some time that high apparent C accumulation rates in recently formed peat are an artefact and take steps to account for it. Here we show, using a model, how the artefact arises. We also demonstrate that increased C accumulation rates in near-surface peat cannot be used to infer that a peatland as a whole is accumulating more C - in fact the reverse can be true because deep peat can be modified by events hundreds of years after it was formed. Our findings highlight that care is needed when evaluating recent C addition to peatlands especially because these interpretations could be wrongly used to inform land use policy and decisions.
Abstract.
Author URL.
Amesbury MJ, Gallego-Sala A, Loisel J (2019). Peatlands as prolific carbon sinks. Nature Geoscience, 12(11), 880-881.
Whittle A, Amesbury MJ, Charman DJ, Hodgson DA, Perren BB, Roberts SJ, Gallego-Sala AV (2019). Salt-Enrichment Impact on Biomass Production in a Natural Population of Peatland Dwelling Arcellinida and Euglyphida (Testate Amoebae).
Microb Ecol,
78(2), 534-538.
Abstract:
Salt-Enrichment Impact on Biomass Production in a Natural Population of Peatland Dwelling Arcellinida and Euglyphida (Testate Amoebae).
Unicellular free-living microbial eukaryotes of the order Arcellinida (Tubulinea; Amoebozoa) and Euglyphida (Cercozoa; SAR), commonly termed testate amoebae, colonise almost every freshwater ecosystem on Earth. Patterns in the distribution and productivity of these organisms are strongly linked to abiotic conditions-particularly moisture availability and temperature-however, the ecological impacts of changes in salinity remain poorly documented. Here, we examine how variable salt concentrations affect a natural community of Arcellinida and Euglyphida on a freshwater sub-Antarctic peatland. We principally report that deposition of wind-blown oceanic salt-spray aerosols onto the peatland surface corresponds to a strong reduction in biomass and to an alteration in the taxonomic composition of communities in favour of generalist taxa. Our results suggest novel applications of this response as a sensitive tool to monitor salinisation of coastal soils and to detect salinity changes within peatland palaeoclimate archives. Specifically, we suggest that these relationships could be used to reconstruct millennial scale variability in salt-spray deposition-a proxy for changes in wind-conditions-from sub-fossil communities of Arcellinida and Euglyphida preserved in exposed coastal peatlands.
Abstract.
Author URL.
Harrison ME, Ottay JB, D’Arcy LJ, Cheyne SM, Anggodo, Belcher C, Cole L, Dohong A, Ermiasi Y, Feldpausch T, et al (2019). Tropical forest and peatland conservation in Indonesia: Challenges and directions.
People and Nature,
2(1), 4-28.
Abstract:
Tropical forest and peatland conservation in Indonesia: Challenges and directions
Abstract
Tropical forests and peatlands provide important ecological, climate and socio‐economic benefits from the local to the global scale. However, these ecosystems and their associated benefits are threatened by anthropogenic activities, including agricultural conversion, timber harvesting, peatland drainage and associated fire. Here, we identify key challenges, and provide potential solutions and future directions to meet forest and peatland conservation and restoration goals in Indonesia, with a particular focus on Kalimantan.
Through a round‐table, dual‐language workshop discussion and literature evaluation, we recognized 59 political, economic, legal, social, logistical and research challenges, for which five key underlying factors were identified. These challenges relate to the 3Rs adopted by the Indonesian Peatland Restoration Agency (Rewetting, Revegetation and Revitalization), plus a fourth R that we suggest is essential to incorporate into (peatland) conservation planning: Reducing Fires.
Our analysis suggests that (a) all challenges have potential for impact on activities under all 4Rs, and many are inter‐dependent and mutually reinforcing, implying that narrowly focused solutions are likely to carry a higher risk of failure; (b) addressing challenges relating to Rewetting and Reducing Fire is critical for achieving goals in all 4Rs, as is considering the local socio‐political situation and acquiring local government and community support; and (c) the suite of challenges faced, and thus conservation interventions required to address these, will be unique to each project, depending on its goals and prevailing local environmental, social and political conditions.
With this in mind, we propose an eight‐step adaptive management framework, which could support projects in both Indonesia and other tropical areas to identify and overcome their specific conservation and restoration challenges.
A free Plain Language Summary can be found within the Supporting Information of this article.
Abstract.
Swindles GT, Morris PJ, Mullan DJ, Payne RJ, Roland TP, Amesbury MJ, Lamentowicz M, Turner TE, Gallego-Sala A, Sim T, et al (2019). Widespread drying of European peatlands in recent centuries. Nature Geoscience, 12(11), 922-928.
Inglis GN, Naafs BDA, Zheng Y, Schellekens J, Pancost RD, Amesbury MJ, Biester H, Bindler R, Blewett J, Burrows MA, et al (2019). delta C-13 values of bacterial hopanoids and leaf waxes as tracers for methanotrophy in peatlands.
GEOCHIMICA ET COSMOCHIMICA ACTA,
260, 244-256.
Author URL.
2018
Inglis GN, Naafs BDA, Zheng Y, McClymont EL, Evershed RP, Pancost RD, the T-GRES Peat Database collaborators (2018). Distributions of geohopanoids in peat: Implications for the use of hopanoid-based proxies in natural archives.
Geochimica et Cosmochimica Acta,
224, 249-261.
Abstract:
Distributions of geohopanoids in peat: Implications for the use of hopanoid-based proxies in natural archives
Hopanoids are pentacyclic triterpenoids produced by a wide range of bacteria. Within modern settings, hopanoids mostly occur in the biological 17β,21β(H) configuration. However, in some modern peatlands, the C31 hopane is present as the ‘thermally-mature’ 17α,21β(H) stereoisomer. This has traditionally been ascribed to isomerisation at the C-17 position catalysed by the acidic environment. However, recent work has argued that temperature and/or hydrology also exert a control upon hopane isomerisation. Such findings complicate the application of geohopanoids as palaeoenvironmental proxies. However, due to the small number of peats that have been studied, as well as the lack of peatland diversity sampled, the environmental controls regulating geohopanoid isomerisation remain poorly constrained. Here, we undertake a global approach to investigate the occurrence, distribution and diagenesis of geohopanoids within peat, combining previously published and newly generated data (n = 395) from peatlands with a wide temperature (−1 to 27 °C) and pH (3–8) range. Our results indicate that peats are characterised by a wide range of geohopanoids. However, the C31 hopane and C32 hopanoic acid (and occasionally the C32 hopanol) typically dominate. C32 hopanoic acids occur as αβ- and ββ-stereoisomers, with the ββ-isomer typically dominating. In contrast, C31 hopanes occur predominantly as the αβ-stereoisomer. These two observations collectively suggest that isomerisation is not inherited from an original biological precursor (i.e. biohopanoids). Using geohopanoid ββ/(αβ + ββ) indices, we demonstrate that the abundance of αβ-hopanoids is strongly influenced by the acidic environment, and we observe a significant positive correlation between C31 hopane isomerisation and pH (n = 94, r2 = 0.64, p 1 pH unit) and longer-term (>1 kyr) variation. Overall, our findings demonstrate the potential of geohopanoids to provide unique new insights into understanding depositional environments and interpreting terrestrial organic matter sources in the geological record.
Abstract.
Zhang H, Gallego-Sala AV, Amesbury M, Charman D, Piilo SR, Väliranta M (2018). Inconsistent response of Arctic permafrost peatland carbon accumulation to warm climate phases.
Global Biogeochemical CyclesAbstract:
Inconsistent response of Arctic permafrost peatland carbon accumulation to warm climate phases
Northern peatlands have accumulated large carbon (C) stocks since the last deglaciation and during past millennia they have acted as important atmospheric C sinks. However, it is still poorly understood how northern peatlands in general and Arctic permafrost peatlands in particular will respond to future climate change. In this study, we present C accumulation reconstructions derived from 14 peat cores from four permafrost peatlands in northeast European Russia and Finnish Lapland. The main focus is on warm climate phases. We used regression analyses to test the importance of different environmental variables such as summer temperature, hydrology and vegetation as drivers for non‐autogenic C accumulation. We used modeling approaches to simulate potential decomposition patterns. The data show that our study sites have been persistent mid‐ to late‐Holocene C sinks with an average accumulation rate of 10.80 – 32.40 g C m‐2 y‐1. The warmer climate phase during the Holocene Thermal Maximum stimulated faster apparent C accumulation rates (ACARs) while the Medieval Climate Anomaly did not. Moreover, during the Little Ice Age, ACARs were controlled more by other factors than by cold climate per se. Although we could not identify any significant environmental factor that drove C accumulation, our data show that recent warming has increased C accumulation in some permafrost peatland sites. However, the synchronous slight decrease of C accumulation in other sites may be an alternative response of these peatlands to warming in the future. This would lead to a decrease in the C sequestration ability of permafrost peatlands overall.
Abstract.
Gallego-Sala AV, Charman D, Brewer S, Page SE, Prentice IC, Friedlingstein P, Moreton S, Amesbury MJ, Beilman DW, Björck S, et al (2018). Latitudinal limits to the predicted increase of the peatland carbon sink with warming. Nature Climate Change, 8, 907-913.
Loisel J, Gallego-Sala A (2018). New research directions for the PAGES C-PEAT working group. Past Global Change Magazine, 26(2), 91-91.
2017
Swindles GT, Morris PJ, Whitney B, Galloway JM, Gałka M, Gallego-Sala AV, Macumber AL, Mullan D, Smith MW, Amesbury MJ, et al (2017). Ecosystem state shifts during long-term development of an Amazonian peatland.
Global Change BiologyAbstract:
Ecosystem state shifts during long-term development of an Amazonian peatland
The most carbon (C) dense ecosystems of Amazonia are areas characterised by the presence of peatlands. However, Amazonian peatland ecosystems are poorly understood and are threatened by human activities. Here we present an investigation into long-term ecohydrological controls on C accumulation in an Amazonian peat dome. This site is the oldest peatland yet discovered in Amazonia (peat initiation c. 8.9 ka BP), and developed in three stages; (i) peat initiated in an abandoned river channel with open water and aquatic plants; (ii) inundated forest swamp; and (iii) raised peat dome (since c. 3.9 ka BP). Local burning occurred at least three times in the past 4,500 years. Two phases of particularly rapid C accumulation (c. 6.6-6.1 and c. 4.9-3.9 ka BP), potentially resulting from increased net primary productivity, were seemingly driven by drier conditions associated with widespread drought events. The association of drought phases with major ecosystem state shifts (open water wetland – forest swamp – peat dome) suggests a potential climatic control on the developmental trajectory of this tropical peatland. A third drought phase centred on c. 1.8-1.1 ka BP led to markedly reduced C accumulation and potentially a hiatus during the peat dome stage. Our results suggest that future droughts may lead to phases of rapid C accumulation in some inundated tropical peat swamps, although this can lead ultimately to a shift to ombrotrophy and a subsequent return to slower C accumulation. Conversely, in ombrotrophic peat domes, droughts may lead to reduced C accumulation or even net loss of peat. Increased surface wetness at our site in recent decades may reflect a shift towards a wetter climate in western Amazonia. Amazonian peatlands represent important carbon stores and habitats, and are important archives of past climatic and ecological information. They should form key foci for conservation efforts.
Abstract.
Davis TW, Prentice IC, Stocker BD, Thomas RT, Whitley RJ, Wang H, Evans BJ, Gallego-Sala AV, Sykes MT, Cramer W, et al (2017). Simple process-led algorithms for simulating habitats (SPLASH v.1.0): Robust indices of radiation, evapotranspiration and plant-available moisture.
Geoscientific Model Development,
10(2), 689-708.
Abstract:
Simple process-led algorithms for simulating habitats (SPLASH v.1.0): Robust indices of radiation, evapotranspiration and plant-available moisture
Bioclimatic indices for use in studies of ecosystem function, species distribution, and vegetation dynamics under changing climate scenarios depend on estimates of surface fluxes and other quantities, such as radiation, evapotranspiration and soil moisture, for which direct observations are sparse. These quantities can be derived indirectly from meteorological variables, such as near-surface air temperature, precipitation and cloudiness. Here we present a consolidated set of simple process-led algorithms for simulating habitats (SPLASH) allowing robust approximations of key quantities at ecologically relevant timescales. We specify equations, derivations, simplifications, and assumptions for the estimation of daily and monthly quantities of top-of-the-atmosphere solar radiation, net surface radiation, photosynthetic photon flux density, evapotranspiration (potential, equilibrium, and actual), condensation, soil moisture, and runoff, based on analysis of their relationship to fundamental climatic drivers. The climatic drivers include a minimum of three meteorological inputs: precipitation, air temperature, and fraction of bright sunshine hours. Indices, such as the moisture index, the climatic water deficit, and the Priestley-Taylor coefficient, are also defined. The SPLASH code is transcribed in C++, FORTRAN, Python, and R. A total of 1 year of results are presented at the local and global scales to exemplify the spatiotemporal patterns of daily and monthly model outputs along with comparisons to other model results.
Abstract.
Zhang H, Amesbury MJ, Ronkainen T, Charman DJ, Gallego-Sala AV, Valiranta M (2017). Testate amoeba as palaeohydrological indicators in the permafrost peatlands of north-east European Russia and Finnish Lapland.
Journal of Quaternary ScienceAbstract:
Testate amoeba as palaeohydrological indicators in the permafrost peatlands of north-east European Russia and Finnish Lapland
To explore the use of testate amoeba for investigating the impacts of climate change on permafrost peatland hydrology, we established a new modern training set from Arctic permafrost peatlands in north-east European Russia and Finnish Lapland. Ordination analyses showed that water-table depth (WTD) was the most important control on testate amoeba distribution. We developed a new testate amoeba-based WTD transfer function and thoroughly tested it. We found that our transfer function had strong predictive power. The best- performing model was based on tolerance-downweighted weighted averaging with inverse deshrinking (R2 1⁄4 0.77, RMSEP 1⁄4 5.62 cm with leave-one-out cross validation). The new transfer function was applied to a short peat core from Arctic Russia and revealed two major hydrological shifts, which could be validated against plant macrofossil data. We also compared our model to another two models from more temperate peatlands. Comparison of the different testate amoeba datasets suggests that testate amoeba ecohydrological relationships are similar for permafrost peatlands to those in more temperate regions, but there are some differences that suggest a need for training datasets that are fully representative of permafrost peatlands.
Abstract.
Gałka M, Szal M, Watson EJ, Gallego-Sala A, Amesbury MJ, Charman DJ, Roland TP, Edward Turner T, Swindles GT (2017). Vegetation Succession, Carbon Accumulation and Hydrological Change in Subarctic Peatlands, Abisko, Northern Sweden.
Permafrost and Periglacial Processes,
28(4), 589-604.
Abstract:
Vegetation Succession, Carbon Accumulation and Hydrological Change in Subarctic Peatlands, Abisko, Northern Sweden
High-resolution analyses of plant macrofossils, testate amoebae, pollen, mineral content, bulk density, and carbon and nitrogen were undertaken to examine the late Holocene dynamics of two permafrost peatlands in Abisko, Subarctic Sweden. The peat records were dated using tephrochronology, 14C and 210Pb. Local plant succession and hydrological changes in peatlands were synchronous with climatic shifts, although autogenous plant succession towards ombrotrophic status during peatland development was also apparent. The Marooned peatland experienced a shift ca. 2250 cal yr BP from rich to poor fen, as indicated by the appearance of Sphagnum fuscum. At Stordalen, a major shift to wetter conditions occurred between 500 and 250 cal yr BP, probably associated with climate change during the Little Ice Age. During the last few decades, the testate amoeba data suggest a deepening of the water table and an increase in shrub pollen, coinciding with recent climate warming and the associated expansion of shrub communities across the Arctic. Rates of carbon accumulation vary greatly between the sites, illustrating the importance of local vegetation communities, hydrology and permafrost dynamics. Multiproxy data elucidate the palaeoecology of S. lindbergii and show that it indicates wet conditions in peatlands. Copyright © 2017 John Wiley & Sons, Ltd.
Abstract.
2016
Gallego-Sala AV, Charman DJ, Harrison SP, Li G, Prentice IC (2016). Climate-driven expansion of blanket bogs in Britain during the Holocene.
Climate of the Past,
12(1), 129-136.
Abstract:
Climate-driven expansion of blanket bogs in Britain during the Holocene
Blanket bog occupies approximately 6 % of the area of the UK today. The Holocene expansion of this hyperoceanic biome has previously been explained as a consequence of Neolithic forest clearance. However, the present distribution of blanket bog in Great Britain can be predicted accurately with a simple model (PeatStash) based on summer temperature and moisture index thresholds, and the same model correctly predicts the highly disjunct distribution of blanket bog worldwide. This finding suggests that climate, rather than land-use history, controls blanket-bog distribution in the UK and everywhere else. We set out to test this hypothesis for blanket bogs in the UK using bioclimate envelope modelling compared with a database of peat initiation age estimates. We used both pollen-based reconstructions and climate model simulations of climate changes between the mid-Holocene (6000 yr BP, 6 ka) and modern climate to drive PeatStash and predict areas of blanket bog. We compiled data on the timing of blanket-bog initiation, based on 228 age determinations at sites where peat directly overlies mineral soil. The model predicts that large areas of northern Britain would have had blanket bog by 6000 yr BP, and the area suitable for peat growth extended to the south after this time. A similar pattern is shown by the basal peat ages and new blanket bog appeared over a larger area during the late Holocene, the greatest expansion being in Ireland, Wales, and southwest England, as the model predicts. The expansion was driven by a summer cooling of about 2 °C, shown by both pollen-based reconstructions and climate models. The data show early Holocene (pre-Neolithic) blanket-bog initiation at over half of the sites in the core areas of Scotland and northern England. The temporal patterns and concurrence of the bioclimate model predictions and initiation data suggest that climate change provides a parsimonious explanation for the early Holocene distribution and later expansion of blanket bogs in the UK, and it is not necessary to invoke anthropogenic activity as a driver of this major landscape change.
Abstract.
Gallego-Sala AV, Booth RK, Charman DJ, Prentice IC, Yu Z (2016). Peatlands and Climate Change. In Bonn A, Allott T, Evans M, Joosten H, Stoneman R (Eds.)
Peatland Restoration and Ecosystem Services
Science, Policy and Practice, Cambridge University Press.
Abstract:
Peatlands and Climate Change
Abstract.
2015
Amesbury MJ, Charman DJ, Newnham RM, Loader NJ, Goodrich J, Royles J, Campbell DI, Keller ED, Baisden WT, Roland TP, et al (2015). Can oxygen stable isotopes be used to track precipitation moisture source in vascular plant-dominated peatlands?.
Earth and Planetary Science Letters,
430, 149-159.
Abstract:
Can oxygen stable isotopes be used to track precipitation moisture source in vascular plant-dominated peatlands?
Variations in the isotopic composition of precipitation are determined by fractionation processes which occur during temperature- and humidity-dependent phase changes associated with evaporation and condensation. Oxygen stable isotope ratios have therefore been frequently used as a source of palaeoclimate data from a variety of proxy archives, which integrate this signal over time. Applications from ombrotrophic peatlands, where the source water used in cellulose synthesis is derived solely from precipitation, have been mostly limited to Northern Hemisphere Sphagnum-dominated bogs, with few in the Southern Hemisphere or in peatlands dominated by vascular plants. New Zealand (NZ) provides an ideal location to undertake empirical research into oxygen isotope fractionation in vascular peatlands because single taxon analysis can be easily carried out, in particular using the preserved root matrix of the restionaceous wire rush (Empodisma spp.) that forms deep Holocene peat deposits throughout the country. Furthermore, large gradients are observed in the mean isotopic composition of precipitation across NZ, caused primarily by the relative influence of different climate modes. Here, we test whether δ18O of Empodisma α-cellulose from ombrotrophic restiad peatlands in NZ can provide a methodology for developing palaeoclimate records of past precipitation δ18O. Surface plant, water and precipitation samples were taken over spatial (six sites spanning >10° latitude) and temporal (monthly measurements over one year) gradients. A link between the isotopic composition of root-associated water, the most likely source water for plant growth, and precipitation in both datasets was found. Back-trajectory modelling of precipitation moisture source for rain days prior to sampling showed clear seasonality in the temporal data that was reflected in root-associated water. The link between source water and plant cellulose was less clear, although mechanistic modelling predicted mean cellulose values within published error margins for both datasets. Improved physiological understanding and modelling of δ18O in restiad peatlands should enable use of this approach as a new source of palaeoclimate data to reconstruct changes in past atmospheric circulation.
Abstract.
Amesbury MJ, Charman DJ, Newnham RM, Loader NJ, Goodrich JP, Royles J, Campbell DI, Roland TP, Gallego-Sala A (2015). Carbon stable isotopes as a palaeoclimate proxy in vascular plant dominated peatlands.
Geochimica et Cosmochimica Acta,
164, 161-174.
Abstract:
Carbon stable isotopes as a palaeoclimate proxy in vascular plant dominated peatlands
Carbon stable isotope (δ13C) records from vascular plant dominated peatlands have been used as a palaeoclimate proxy, but a better empirical understanding of fractionation processes in these ecosystems is required. Here, we test the potential of δ13C analysis of ombrotrophic restiad peatlands in New Zealand, dominated by the wire rush (Empodisma spp.), to provide a methodology for developing palaeoclimatic records. We took surface plant samples alongside measurements of water table depth and (micro)climate over spatial (six sites spanning>10° latitude) and temporal (monthly measurements over 1year) gradients and analysed the relationships between cellulose δ13C values and environmental parameters. We found strong, significant negative correlations between δ13C and temperature, photosynthetically active radiation and growing degree days above 0°C. No significant relationships were observed between δ13C and precipitation, relative humidity, soil moisture or water table depth, suggesting no growing season water limitation and a decoupling of the expected link between δ13C in vascular plants and hydrological variables. δ13C of Empodisma spp. roots may therefore provide a valuable temperature proxy in a climatically sensitive region, but further physiological and sub-fossil calibration studies are required to fully understand the observed signal.
Abstract.
Xing W, Bao K, Gallego-Sala AV, Charman DJ, Zhang Z, Gao C, Lu X, Wang G (2015). Climate Controls on carbon accumulation in peatlands of Northeast China.
Quaternary Science Reviews,
115, 78-88.
Abstract:
Climate Controls on carbon accumulation in peatlands of Northeast China
Peatlands contain around one third of the global soil carbon (C) and play an important role in the C cycle. In particular, the response of the productivity-decay balance to climate variability is critical for understanding both the past and future global C cycle. Most studies of peatland C dynamics have been carried out on boreal and subarctic peatlands, where climate models predict a greater increase in temperature compared to the global average. Less is known about peatlands at lower latitudes, yet there are significant peatland C stocks in these regions that may be more vulnerable to future climate change because they are closer to the climatic limit of peatland distribution. Northeast China is China's largest wetland region, with extensive peatlands in mountain regions and across the plains. Here, we used core data from 134 peatland sites to quantify the C accumulation rate over different timescales and estimate C storage across northeast China. The results show that the Holocene long-term apparent rate of C accumulation (LORCA) ranged from 5.74 to 129.31 g C m−2 yr−1, with a mean rate of 33.66 g C m−2 yr−1. The total wetland area and C storage within this region is 82,870 km2 and 4.34 Gt C, and about 80% of the C is contained in mountain peatlands. We find that total C accumulated over the last 2000 years is linearly related to photosynthetically active radiation over the growing season, supporting the hypothesis that rates of net primary productivity (NPP) are more important than decomposition rates in determining long-term C accumulation. Although peatlands in northeast China are close to the southern limit of major peatland extent, our data suggest that future warming will lead to greater future C accumulation, as long as moisture balance or cloudiness do not become limiting factors.
Abstract.
Gallego-Sala AV, Charman DJ, Harrison SP, Li G, Prentice IC (2015). Climate-driven expansion of blanket bogs in Britain during the Holocene.
Clim. Past Discuss.,
11, 4811-4832.
Abstract:
Climate-driven expansion of blanket bogs in Britain during the Holocene
Blanket bog occupies approximately 6 % of the area of the UK today. The Holocene expansion of this hyperoceanic biome has previously been explained as a consequence of Neolithic forest clearance. However, the present distribution of blanket bog in Great Britain can be predicted accurately with a simple model (PeatStash) based on summer temperature and moisture index thresholds, and the same model correctly predicts the highly disjunct distribution of blanket bog worldwide. This finding suggests that climate, rather than land-use history, controls blanket-bog distribution in the UK and everywhere else.
We set out to test this hypothesis for blanket bogs in the UK using bioclimate envelope modelling compared with a database of peat initiation age estimates. We used both pollen-based reconstructions and climate model simulations of climate changes between the mid-Holocene (6000 yr BP, 6 ka) and modern climate to drive PeatStash and predict areas of blanket bog. We compiled data on the timing of blanket-bog initiation, based on 228 age determinations at sites where peat directly overlies mineral soil. The model predicts large areas of northern Britain would have had blanket bog by 6000 yr BP, and the area suitable for peat growth extended to the south after this time. A similar pattern is shown by the basal peat ages and new blanket bog appeared over a larger area during the late Holocene, the greatest expansion being in Ireland, Wales and southwest England, as the model predicts. The expansion was driven by a summer cooling of about 2 °C, shown by both pollen-based reconstructions and climate models. The data show early Holocene (pre-Neolithic) blanket-bog initiation at over half of the sites in the core areas of Scotland, and northern England.
The temporal patterns and concurrence of the bioclimate model predictions and initiation data suggest that climate change provides a parsimonious explanation for the early Holocene distribution and later expansion of blanket bogs in the UK, and it is not necessary to invoke anthropogenic activity as a driver of this major landscape change.
Abstract.
Charman DJ, Amesbury MJ, Hinchliffe W, Hughes PDM, Mallon G, Blake WH, Daley TJ, Gallego-Sala AV, Mauquoy D (2015). Drivers of Holocene peatland carbon accumulation across a climate gradient in northeastern North America.
Quaternary Science Reviews,
121, 110-119.
Abstract:
Drivers of Holocene peatland carbon accumulation across a climate gradient in northeastern North America
Peatlands are an important component of the Holocene global carbon (C) cycle and the rate of C sequestration and storage is driven by the balance between net primary productivity and decay. A number of studies now suggest that climate is a key driver of peatland C accumulation at large spatial scales and over long timescales, with warmer conditions associated with higher rates of C accumulation. However, other factors are also likely to play a significant role in determining local carbon accumulation rates and these may modify past, present and future peatland carbon sequestration. Here, we test the importance of climate as a driver of C accumulation, compared with hydrological change, fire, nitrogen content and vegetation type, from records of C accumulation at three sites in northeastern North America, across the N-S climate gradient of raised bog distribution. Radiocarbon age models, bulk density values and %C measurements from each site are used to construct C accumulation histories commencing between 11,200 and 8000cal. years BP. The relationship between C accumulation and environmental variables (past water table depth, fire, peat forming vegetation and nitrogen content) is assessed with linear and multivariate regression analyses. Differences in long-term rates of carbon accumulation between sites support the contention that a warmer climate with longer growing seasons results in faster rates of long-term carbon accumulation. However, mid-late Holocene accumulation rates show divergent trends, decreasing in the north but rising in the south. We hypothesise that sites close to the moisture threshold for raised bog distribution increased their growth rate in response to a cooler climate with lower evapotranspiration in the late Holocene, but net primary productivity declined over the same period in northern areas causing a decrease in C accumulation. There was no clear relationship between C accumulation and hydrological change, vegetation, nitrogen content or fire, but early successional stages of peatland growth had faster rates of C accumulation even though temperatures were probably lower at the time. We conclude that climate is the most important driver of peatland accumulation rates over millennial timescales, but that successional vegetation change is a significant additional influence. Whilst the majority of northern peatlands are likely to increase C accumulation rates under future warmer climates, those at the southern limit of distribution may show reduced rates. However, early succession peatlands that develop under future warming at the northern limits of peatland distribution are likely to have high rates of C accumulation and will compensate for some of the losses elsewhere.
Abstract.
Swindles GT, Morris PJ, Mullan D, Watson EJ, Turner E, Roland TP, Amesbury MJ, Kokfelt U, Schoning K, Pratte S, et al (2015). The long-term fate of permafrost peatlands under rapid climate warming.
Scientific Reports,
5Abstract:
The long-term fate of permafrost peatlands under rapid climate warming
Permafrost peatlands contain globally important amounts of soil organic carbon, owing to cold conditions which suppress anaerobic decomposition. However, climate warming and permafrost thaw threaten the stability of this carbon store. The ultimate fate of permafrost peatlands and their carbon stores is unclear because of complex feedbacks between peat accumulation, hydrology and vegetation. Field monitoring campaigns only span the last few decades and therefore provide an incomplete picture of permafrost peatland response to recent rapid warming. Here we use a high-resolution palaeoecological approach to understand the longer-term response of peatlands in contrasting states of permafrost degradation to recent rapid warming. At all sites we identify a drying trend until the late-twentieth century; however, two sites subsequently experienced a rapid shift to wetter conditions as permafrost thawed in response to climatic warming, culminating in collapse of the peat domes. Commonalities between study sites lead us to propose a five-phase model for permafrost peatland response to climatic warming. This model suggests a shared ecohydrological trajectory towards a common end point: inundated Arctic fen. Although carbon accumulation is rapid in such sites, saturated soil conditions are likely to cause elevated methane emissions that have implications for climate-feedback mechanisms.
Abstract.
Bohn TJ, Melton JR, Ito A, Kleinen T, Spahni R, Stocker BD, Zhang B, Zhu X, Schroeder R, Glagolev MV, et al (2015). WETCHIMP-WSL: Intercomparison of wetland methane emissions models over West Siberia.
Biogeosciences,
12(11), 3321-3349.
Abstract:
WETCHIMP-WSL: Intercomparison of wetland methane emissions models over West Siberia
Wetlands are the world's largest natural source of methane, a powerful greenhouse gas. The strong sensitivity of methane emissions to environmental factors such as soil temperature and moisture has led to concerns about potential positive feedbacks to climate change. This risk is particularly relevant at high latitudes, which have experienced pronounced warming and where thawing permafrost could potentially liberate large amounts of labile carbon over the next 100 years. However, global models disagree as to the magnitude and spatial distribution of emissions, due to uncertainties in wetland area and emissions per unit area and a scarcity of in situ observations. Recent intensive field campaigns across the West Siberian Lowland (WSL) make this an ideal region over which to assess the performance of large-scale process-based wetland models in a high-latitude environment. Here we present the results of a follow-up to the Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP), focused on the West Siberian Lowland (WETCHIMP-WSL). We assessed 21 models and 5 inversions over this domain in terms of total CH4 emissions, simulated wetland areas, and CH4 fluxes per unit wetland area and compared these results to an intensive in situ CH4 flux data set, several wetland maps, and two satellite surface water products. We found that (a) despite the large scatter of individual estimates, 12-year mean estimates of annual total emissions over the WSL from forward models (5.34 ± 0.54 Tg CH4 yrg'1), inversions (6.06 ± 1.22 Tg CH4 yrg'1), and in situ observations (3.91 ± 1.29 Tg CH4 yrg'1) largely agreed; (b) forward models using surface water products alone to estimate wetland areas suffered from severe biases in CH4 emissions; (c) the interannual time series of models that lacked either soil thermal physics appropriate to the high latitudes or realistic emissions from unsaturated peatlands tended to be dominated by a single environmental driver (inundation or air temperature), unlike those of inversions and more sophisticated forward models; (d) differences in biogeochemical schemes across models had relatively smaller influence over performance; and (e) multiyear or multidecade observational records are crucial for evaluating models' responses to long-term climate change.
Abstract.
2014
Swindles GT, Reczuga M, Lamentowicz M, Raby CL, Turner TE, Charman DJ, Gallego-Sala AV, Valderrama E, Williams C, Draper F, et al (2014). Ecology of Testate Amoebae in an Amazonian Peatland and Development of a Transfer Function
for Palaeohydrological Reconstruction.
Microbial Ecology: an international journalAbstract:
Ecology of Testate Amoebae in an Amazonian Peatland and Development of a Transfer Function
for Palaeohydrological Reconstruction
Tropical peatlands represent globally important carbon sinks with a unique biodiversity and are currently threatened by climate change and human activities. It is now imperative that proxy methods are developed to understand the ecohydrological dynamics of these sys- tems and for testing peatland development models. Testate amoebae have been used as environmental indicators in ecological and palaeoecological studies of peatlands, pri- marily in ombrotrophic Sphagnum-dominated peatlands in the mid- and high-latitudes. We present the first ecolog- ical analysis of testate amoebae in a tropical peatland, a nutrient-poor domed bog in western (Peruvian) Amazonia. Litter samples were collected from different hydrological microforms (hummock to pool) along a transect from the edge to the interior of the peatland. We recorded 47 taxa from 21 genera. The most common taxa are Cryptodifflugia oviformis, Euglypha rotunda type, Phryganella acropodia, Pseudodifflugia fulva type and Trinema lineare. One species found only in the southern hemisphere, Argynnia spicata, is present. Arcella spp. Centropyxis aculeata and Lesqueresia spiralis are indicators of pools containing standing water. Canonical correspondence analysis and non-metric multi- dimensional scaling illustrate that water table depth is a significant control on the distribution of testate amoebae, similar to the results from mid- and high-latitudes peat- lands. A transfer function model for water table based on weighted averaging partial least-squares (WAPLS) regres- sion is presented and performs well under cross-validation (r2apparent = 0.76, RMSE = 4.29; r2jack = 0.68, RMSEP = 5.18). The transfer function was applied to a 1-m peat core, and sample-specific reconstruction errors were generated using bootstrapping. The reconstruction generally suggests near-surface water tables over the last 3,000 years, with a shift to drier conditions at c. cal. 1218-1273 AD.
Abstract.
Swindles GT, Reczuga M, Lamentowicz M, Raby CL, Turner TE, Charman DJ, Gallego-Sala A, Valderrama E, Williams C, Draper F, et al (2014). Ecology of Testate Amoebae in an Amazonian Peatland and Development of a Transfer Function for Palaeohydrological Reconstruction.
Microbial Ecology,
68(2), 284-298.
Abstract:
Ecology of Testate Amoebae in an Amazonian Peatland and Development of a Transfer Function for Palaeohydrological Reconstruction
Tropical peatlands represent globally important carbon sinks with a unique biodiversity and are currently threatened by climate change and human activities. It is now imperative that proxy methods are developed to understand the ecohydrological dynamics of these systems and for testing peatland development models. Testate amoebae have been used as environmental indicators in ecological and palaeoecological studies of peatlands, primarily in ombrotrophic Sphagnum-dominated peatlands in the mid- and high-latitudes. We present the first ecological analysis of testate amoebae in a tropical peatland, a nutrient-poor domed bog in western (Peruvian) Amazonia. Litter samples were collected from different hydrological microforms (hummock to pool) along a transect from the edge to the interior of the peatland. We recorded 47 taxa from 21 genera. The most common taxa are Cryptodifflugia oviformis, Euglypha rotunda type, Phryganella acropodia, Pseudodifflugia fulva type and Trinema lineare. One species found only in the southern hemisphere, Argynnia spicata, is present. Arcella spp. Centropyxis aculeata and Lesqueresia spiralis are indicators of pools containing standing water. Canonical correspondence analysis and non-metric multidimensional scaling illustrate that water table depth is a significant control on the distribution of testate amoebae, similar to the results from mid- and high-latitude peatlands. A transfer function model for water table based on weighted averaging partial least-squares (WAPLS) regression is presented and performs well under cross-validation (rapparent = 0.76, RMSE = 4.29; r2jack = 0.68, RMSEP = 5.18). The transfer function was applied to a 1-m peat core, and sample-specific reconstruction errors were generated using bootstrapping. The reconstruction generally suggests near-surface water tables over the last 3,000 years, with a shift to drier conditions at c. cal. 1218-1273 AD. © 2014 Springer Science+Business Media New York.
Abstract.
Holmquist JR, MacDonald GM, Gallego-Sala AV (2014). Peatland Initiation, Carbon Accumulation, and 2 ka Depth in the James Bay Lowland and Adjacent Regions.
Arctic, Antarctic, and Alpine Research,
46(1), 19-39.
Abstract:
Peatland Initiation, Carbon Accumulation, and 2 ka Depth in the James Bay Lowland and Adjacent Regions
Peatlands surrounding Hudson and James Bays form the second largest peatland complex in the world and contain major stores of soil carbon (C). This study utilized a transect of eight ombrotrophic peat cores from remote regions of central and northern Ontario to quantify the magnitude and rate of C accumulation since peatland initiation and for the past 2000 calendar years before present (2 ka). These new data were supplemented by 17 millennially resolved chronologies from a literature review covering the Boreal Shield, Hudson Plains, and Taiga Shield bordering Hudson and James Bays. Peatlands initiated in central and northern Ontario by 7.8 ka following deglaciation and isostatic emergence of northern areas to above sea level. Total C accumulated since inception averaged 109.7 ± (std. dev.) 36.2 kg C m–2. Approximately 40% of total soil C has accumulated since 2 ka at an average apparent rate of 20.2 ± 6.9 g C m–2 yr–1. The 2 ka depths correlate significantly and positively with modern gridded climate estimates for mean annual precipitation, mean annual air temperature, growing degree-days > 0 °C, and photosynthetically active radiation integrated over days > 0 °C. There are significantly shallower depths in permafrost peatlands. Vertical peat accumulation was likely constrained by temperature, growing season length, and photosynthetically active radiation over the last 2 ka in the Hudson Bay Lowlands and surrounding regions.
Abstract.
2013
Regnier P, Friedlingstein P, Ciais P, Mackenzie FT, Gruber N, Janssens IA, Laruelle GG, Lauerwald R, Luyssaert S, Andersson AJ, et al (2013). Anthropogenic perturbation of the carbon fluxes from land to ocean.
Nature Geoscience,
6(8), 597-607.
Abstract:
Anthropogenic perturbation of the carbon fluxes from land to ocean
A substantial amount of the atmospheric carbon taken up on land through photosynthesis and chemical weathering is transported laterally along the aquatic continuum from upland terrestrial ecosystems to the ocean. So far, global carbon budget estimates have implicitly assumed that the transformation and lateral transport of carbon along this aquatic continuum has remained unchanged since pre-industrial times. A synthesis of published work reveals the magnitude of present-day lateral carbon fluxes from land to ocean, and the extent to which human activities have altered these fluxes. We show that anthropogenic perturbation may have increased the flux of carbon to inland waters by as much as 1.0 Pg C yr -1 since pre-industrial times, mainly owing to enhanced carbon export from soils. Most of this additional carbon input to upstream rivers is either emitted back to the atmosphere as carbon dioxide (∼0.4 Pg C yr -1) or sequestered in sediments (∼0.5 Pg C yr -1) along the continuum of freshwater bodies, estuaries and coastal waters, leaving only a perturbation carbon input of ∼0.1 Pg C yr -1 to the open ocean. According to our analysis, terrestrial ecosystems store ∼0.9 Pg C yr -1 at present, which is in agreement with results from forest inventories but significantly differs from the figure of 1.5 Pg C yr -1 previously estimated when ignoring changes in lateral carbon fluxes. We suggest that carbon fluxes along the land-ocean aquatic continuum need to be included in global carbon dioxide budgets.
Abstract.
Charman DJ, Beilman DW, Blaauw M, Booth RK, Brewer S, Chambers FM, Christen JA, Gallego-Sala A, Harrison SP, Hughes PDM, et al (2013). Climate-related changes in peatland carbon accumulation during the last millennium.
Biogeosciences,
10(2), 929-944.
Abstract:
Climate-related changes in peatland carbon accumulation during the last millennium
Peatlands are a major terrestrial carbon store and a persistent natural carbon sink during the Holocene, but there is considerable uncertainty over the fate of peatland carbon in a changing climate. It is generally assumed that higher temperatures will increase peat decay, causing a positive feedback to climate warming and contributing to the global positive carbon cycle feedback. Here we use a new extensive database of peat profiles across northern high latitudes to examine spatial and temporal patterns of carbon accumulation over the past millennium. Opposite to expectations, our results indicate a small negative carbon cycle feedback from past changes in the long-term accumulation rates of northern peatlands. Total carbon accumulated over the last 1000 yr is linearly related to contemporary growing season length and photosynthetically active radiation, suggesting that variability in net primary productivity is more important than decomposition in determining long-term carbon accumulation. Furthermore, northern peatland carbon sequestration rate declined over the climate transition from the Medieval Climate Anomaly (MCA) to the Little Ice Age (LIA), probably because of lower LIA temperatures combined with increased cloudiness suppressing net primary productivity. Other factors including changing moisture status, peatland distribution, fire, nitrogen deposition, permafrost thaw and methane emissions will also influence future peatland carbon cycle feedbacks, but our data suggest that the carbon sequestration rate could increase over many areas of northern peatlands in a warmer future. © 2012 Author(s).
Abstract.
2012
Gallego-Sala AV, Prentice C (2012). Blanket peat biome endangered by climate change.
Nature Climate ChangeAbstract:
Blanket peat biome endangered by climate change
Blanket bog is a highly distinctive biome restricted to disjunct hyperoceanic regions. It is characterized by a landscape covering of peat broken only by the steepest slopes1. Plant and microbial life are adapted to anoxia, low pH and low nutrient availability. Plant productivity exceeds soil organic matter decomposition, so carbon is sequestered over time. Unique climatic requirements, including high year-round rainfall and low summer temperatures2, make this biome amenable to bioclimatic modelling. However, projections of the fate of peatlands in general, and blanket bogs in particular, under climate change have been contradictory3, 4, 5, 6, 7. Here we use a simple, well-founded global bioclimatic model8, with climate-change projections from seven climate models, to indicate this biome’s fate. We show marked shrinkage of its present bioclimatic space with only a few, restricted areas of persistence. Many blanket bog regions are thus at risk of progressive peat erosion and vegetation changes as a direct consequence of climate change. New areas suitable for blanket bog are also projected, but these are often disjunct from present areas and their location is inconsistently predicted by different climate models.
Abstract.
Charman DJ, and 40 others (2012). Climate-related changes in peatland carbon accumulation during the last millennium. Biogeosciences Discussions, 9, 14327-14364.
Loisel J, Gallego-Sala AV, Yu Z (2012). Global-scale pattern of peatland Sphagnum growth driven by photosynthetically active radiation and growing season length.
Biogeosciences,
9(7), 2737-2746.
Abstract:
Global-scale pattern of peatland Sphagnum growth driven by photosynthetically active radiation and growing season length
High-latitude peatlands contain about one third of the world's soil organic carbon, most of which is derived from partly decomposed Sphagnum (peat moss) plants. We conducted a meta-analysis based on a global data set of Sphagnum growth measurements collected from published literature to investigate the effects of bioclimatic variables on Sphagnum growth. Analysis of variance and general linear models were used to relate Sphagnum magellanicum and S. fuscum growth rates to photosynthetically active radiation integrated over the growing season (PAR0) and a moisture index. We found that PAR0 was the main predictor of Sphagnum growth for the global data set, and effective moisture was only correlated with moss growth at continental sites. The strong correlation between Sphagnum growth and PAR0 suggests the existence of a global pattern of growth, with slow rates under cool climate and short growing seasons, highlighting the important role of growing season length in explaining peatland biomass production. Large-scale patterns of cloudiness during the growing season might also limit moss growth. Although considerable uncertainty remains over the carbon balance of peatlands under a changing climate, our results suggest that increasing PAR0 as a result of global warming and lengthening growing seasons, without major change in cloudiness, could promote Sphagnum growth. Assuming that production and decomposition have the same sensitivity to temperature, this enhanced growth could lead to greater peat-carbon sequestration, inducing a negative feedback to climate change. © 2012 Author(s). CC Attribution 3.0 License.
Abstract.
Loisel J, Gallego-Sala AV, Yu Z (2012). Global-scale pattern of peatland Sphagnum growth driven by photosynthetically active radiation and growing season length. , 9(2), 2169-2196.
Leifeld J, Steffens M, Galego-Sala A (2012). Sensitivity of peatland carbon loss to organic matter quality. Geophysical Research Letters, 39(14), n/a-n/a.
2010
Clark JM, Gallego-Sala AV, Allott TEH, Chapman SJ, Farewell T, Freeman C, House JI, Orr HG, Prentice IC, Smith P, et al (2010). Assessing the vulnerability of blanket peat to climate change using an ensemble of statistical bioclimatic envelope models.
Climate Research,
45(1), 131-150.
Abstract:
Assessing the vulnerability of blanket peat to climate change using an ensemble of statistical bioclimatic envelope models
We assessed the vulnerability of blanket peat to climate change in Great Britain using an ensemble of 8 bioclimatic envelope models. We used 4 published models that ranged from simple threshold models, based on total annual precipitation, to Generalised Linear Models (GLMs, based on mean annual temperature). In addition, 4 new models were developed which included measures of water deficit as threshold, classification tree, GLM and generalised additive models (GAM). Models that included measures of both hydrological conditions and maximum temperature provided a better fit to the mapped peat area than models based on hydrological variables alone. Under UKCIP02 projections for high (A1F1) and low (B1) greenhouse gas emission scenarios, 7 out of the 8 models showed a decline in the bioclimatic space associated with blanket peat. Eastern regions (Northumbria, North York Moors, Orkney) were shown to be more vulnerable than higher-altitude, western areas (Highlands, Western Isles and Argyle, Bute and the Trossachs). These results suggest a long-term decline in the distribution of actively growing blanket peat, especially under the high emissions scenario, although it is emphasised that existing peatlands may well persist for decades under a changing climate. Observational data from long-term monitoring and manipulation experiments in combination with process-based models are required to explore the nature and magnitude of climate change impacts on these vulnerable areas more fully. © Inter-Research 2010.
Abstract.
Gallego-Sala AV, Clark JM, House JI, Orr HG, Prentice IC, Smith P, Farewell T, Chapman SJ (2010). Bioclimatic envelope model of climate change impacts on blanket peatland distribution in Great Britain.
Climate Research,
45(1), 151-162.
Abstract:
Bioclimatic envelope model of climate change impacts on blanket peatland distribution in Great Britain
Blanket peatlands are rain-fed mires that cover the landscape almost regardless of topography. The geographical extent of this type of peatland is highly sensitive to climate. We applied a global process-based bioclimatic envelope model, PeatStash, to predict the distribution of British blanket peatlands. The model captures the present areal extent (Kappa = 0.77) and is highly sensitive to both temperature and precipitation changes. When the model is run using the UKCIP02 climate projections for the time periods 2011-2040, 2041-2070 and 2071-2100, the geographical distribution of blanket peatlands gradually retreats towards the north and the west. In the UKCIP02 high emissions scenario for 2071-2100, the blanket peatland bioclimatic space is ∼84% smaller than contemporary conditions (1961-1990); only parts of the west of Scotland remain inside this space. Increasing summer temperature is the main driver of the projected changes in areal extent. Simulations using 7 climate model outputs resulted in generally similar patterns of declining aereal extent of the bioclimatic space, although differing in degree. The results presented in this study should be viewed as a first step towards understanding the trends likely to affect the blanket peatland distribution in Great Britain. The eventual fate of existing blanket peatlands left outside their bioclimatic space remains uncertain. © Inter-Research 2010.
Abstract.
House JI, Orr HG, Clark JM, Gallego-Sala AV, Freeman C, Prentice IC, Smith P (2010). Climate change and the British Uplands: Evidence for decision-making.
Climate Research,
45(1), 3-12.
Abstract:
Climate change and the British Uplands: Evidence for decision-making
We summarise the work of an interdisciplinary network set up to explore the impacts of climate change in the British Uplands. In this CR Special, the contributors present the state of knowledge and this introduction synthesises this knowledge and derives implications for decision makers. The Uplands are valued semi-natural habitats, providing ecosystem services that have historically been taken for granted. For example, peat soils, which are mostly found in the Uplands, contain around 50% of the terrestrial carbon in the UK. Land management continues to be a driver of ecosystem service delivery. Degraded and managed peatlands are subject to erosion and carbon loss with negative impacts on biodiversity, carbon storage and water quality. Climate change is already being experienced in British Uplands and is likely to exacerbate these pressures. Climate envelope models suggest as much as 50% of British Uplands and peatlands will be exposed to climate stress by the end of the 21st century under low and high emissions scenarios. However, process-based models of the response of organic soils to this climate stress do not give a consistent indication of what this will mean for soil carbon: results range from a very slight increase in uptake, through a clear decline, to a net carbon loss. Preserving existing peat stocks is an important climate mitigation strategy, even if new peat stops forming. Preserving upland vegetation cover is a key win-win management strategy that will reduce erosion and loss of soil carbon, and protect a variety of services such as the continued delivery of a high quality water resource. © Inter-Research 2010.
Abstract.
Clark JM, Billett MF, Coyle M, Croft S, Daniels S, Evans CD, Evans M, Freeman C, Gallego-Sala AV, Heinemeyer A, et al (2010). Model inter-comparison between statistical and dynamic model assessments of the long-term stability of blanket PEAT in great britain (1940-2099).
Climate Research,
45(1), 227-248.
Abstract:
Model inter-comparison between statistical and dynamic model assessments of the long-term stability of blanket PEAT in great britain (1940-2099)
We compared output from 3 dynamic process-based models (DMs: ECOSSE, MILLENNIA and the Durham Carbon Model) and 9 bioclimatic envelope models (BCEMs; including BBOG ensemble and PEATSTASH) ranging from simple threshold to semi-process-based models. Model simulations were run at 4 British peatland sites using historical climate data and climate projections under a medium (A1B) emissions scenario from the 11-RCM (regional climate model) ensemble underpinning UKCP09. The models showed that blanket peatlands are vulnerable to projected climate change; however, predictions varied between models as well as between sites. All BCEMs predicted a shift from presence to absence of a climate associated with blanket peat, where the sites with the lowest total annual precipitation were closest to the presence/absence threshold. DMs showed a more variable response. ECOSSE predicted a decline in net C sink and shift to net C source by the end of this century. The Durham Carbon Model predicted a smaller decline in the net C sink strength, but no shift to net C source. MILLENNIA predicted a slight overall increase in the net C sink. In contrast to the BCEM projections, the DMs predicted that the sites with coolest temperatures and greatest total annual precipitation showed the largest change in carbon sinks. In this model inter-comparison, the greatest variation in model output in response to climate change projections was not between the BCEMs and DMs but between the DMs themselves, because of different approaches to modelling soil organic matter pools and decomposition amongst other processes. The difference in the sign of the response has major implications for future climate feedbacks, climate policy and peatland management. Enhanced data collection, in particular monitoring peatland response to current change, would significantly improve model development and projections of future change. © Inter-Research 2010.
Abstract.
2009
Nisbet RER, Fisher R, Nimmo RH, Bendall DS, Crill PM, Gallego-Sala AV, Hornibrook ERC, López-Juez E, Lowry D, Nisbet PBR, et al (2009). Emission of methane from plants.
Proceedings of the Royal Society B: Biological Sciences,
276(1660), 1347-1354.
Abstract:
Emission of methane from plants
It has been proposed that plants are capable of producing methane by a novel and unidentified biochemical pathway. Emission of methane with an apparently biological origin was recorded from both whole plants and detached leaves. This was the first report of methanogenesis in an aerobic setting, and was estimated to account for 10-45 per cent of the global methane source. Here, we show that plants do not contain a known biochemical pathway to synthesize methane. However, under high UV stress conditions, there may be spontaneous breakdown of plant material, which releases methane. In addition, plants take up and transpire water containing dissolved methane, leading to the observation that methane is released. Together with a new analysis of global methane levels from satellite retrievals, we conclude that plants are not a major source of the global methane production. © 2009 the Royal Society.
Abstract.
Nisbet RER, Fisher R, Nimmo RH, Bendall DS, Crill PM, Gallego-Sala AV, Hornibrook ERC, López-Juez E, Lowry D, Nisbet PBR, et al (2009). Emission of methane from plants.
Proc Biol Sci,
276(1660), 1347-1354.
Abstract:
Emission of methane from plants.
It has been proposed that plants are capable of producing methane by a novel and unidentified biochemical pathway. Emission of methane with an apparently biological origin was recorded from both whole plants and detached leaves. This was the first report of methanogenesis in an aerobic setting, and was estimated to account for 10-45 per cent of the global methane source. Here, we show that plants do not contain a known biochemical pathway to synthesize methane. However, under high UV stress conditions, there may be spontaneous breakdown of plant material, which releases methane. In addition, plants take up and transpire water containing dissolved methane, leading to the observation that methane is released. Together with a new analysis of global methane levels from satellite retrievals, we conclude that plants are not a major source of the global methane production.
Abstract.
Author URL.
Hornibrook ERC, Bowes HL, Culbert A, Gallego-Sala AV (2009). Methanotrophy potential versus methane supply by pore water diffusion in peatlands.
Biogeosciences,
6(8), 1491-1504.
Abstract:
Methanotrophy potential versus methane supply by pore water diffusion in peatlands
Low affinity methanotrophic bacteria consume a significant quantity of methane in wetland soils in the vicinity of plant roots and at the oxic-anoxic interface. Estimates of the efficiency of methanotrophy in peat soils vary widely in part because of differences in approaches employed to quantify methane cycling. High resolution profiles of dissolved methane abundance measured during the summer of 2003 were used to quantity rates of upward methane flux in four peatlands situated in Wales, UK. Aerobic incubations of peat from a minerotrophic and an ombrotrophic mire were used to determine depth distributions of kinetic parameters associated with methane oxidation. The capacity for methanotrophy in a 3 cm thick zone immediately beneath the depth of nil methane abundance in pore water was significantly greater than the rate of upward diffusion of methane in all four peatlands. Rates of methane diffusion in pore water at the minerotrophic peatlands were small (
Abstract.
Friedlingstein P, Gallego-Sala AV, Blyth EM, Hewer FE, Seneviratne SI, Spessa A, Suntharalingam P, Scholze M (2009). The earth system feedbacks that matter for contemporary climate. In (Ed)
Understanding the Earth System: Global Change Science for Application, 102-128.
Abstract:
The earth system feedbacks that matter for contemporary climate
Abstract.
2008
Hornibrook ERC, Bowes HL, Culbert A, Gallego-Sala AV (2008). Methanotrophy potential versus methane supply by pore water diffusion in peatlands. , 5(3), 2607-2643.
1999
Gallego-Sala AV, Kennedy KM, Chadwick AV, Niemeier D, Becker KD (1999). An EXAFS and computer modelling study of calcium titanite.
RADIATION EFFECTS AND DEFECTS IN SOLIDS,
151(1-4), 13-19.
Author URL.
Gallego-Sala AV, Kennedy KM, Chadwick AV, Niemeier D, Becker KD (1999). EXAFS and computer modelling study of calcium titanite.
Radiation Effects and Defects in Solids,
151(1), 13-19.
Abstract:
EXAFS and computer modelling study of calcium titanite
Calcium titanite CaTiSiO5 undergoes a phase transition at approximately 220 °C. Extended X-ray Absorption Fine Structure (EXAFS) spectra of both calcium and titanium K-edge have been collected and local structural information extracted from them. The results have been compared with the existing XRD data on this material and the agreement is excellent. In particular, there is good agreement on the changes in bond lengths that occur at the phase transition. A complementary computer simulation study has also been performed and defect formation energies have been calculated.
Abstract.
