Publications by year
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.
Divergent responses of permafrost peatlands to recent climate change
&lt;p&gt;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. &amp;#160;&amp;#160;&lt;/p&gt; Abstract
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
Charman D, Amesbury MJ, Roland TP, Royles J, Hodgson DA, Convey P, Griffiths H (In Press). Spatially coherent late-Holocene Antarctic Peninsula surface air temperature variability. Geology
Barión PH, Roberts SJ, Spiegel C, Binnie SA, Wacker L, Davies J, Gabriel I, Jones VJ, Blockley S, Pearson EJ, et al (2023). Holocene deglaciation and glacier readvances on the Fildes Peninsula and King George Island (Isla 25 de Mayo), South Shetland Islands, NW Antarctic Peninsula. The Holocene, 33(6), 636-658.
Heredia Barión P, Roberts S, Spiegel C, Binnie S, Wacker L, Davies J, Gabriel I, Jones V, Blockley S, Pearson E, et al (2023). Holocene deglaciation and glacier readvances on the Fildes Peninsula and King George Island (Isla 25 de Mayo), South Shetland Islands, NW Antarctic Peninsula.
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.
Swindles GT, Roland TP, Ruffell A (2023). The ‘Anthropocene’ is most useful as an informal concept. Journal of Quaternary Science, 38(4), 453-454.
Zhang H, Väliranta M, Swindles GT, Aquino-López MA, Mullan D, Tan N, Amesbury M, Babeshko KV, Bao K, Bobrov A, et al
(2022). Recent climate change has driven divergent hydrological shifts in high-latitude peatlands. Nat Commun
Recent climate change has driven divergent hydrological shifts in high-latitude peatlands.
High-latitude peatlands are changing rapidly in response to climate change, including permafrost thaw. Here, we reconstruct hydrological conditions since the seventeenth century using testate amoeba data from 103 high-latitude peat archives. We show that 54% of the peatlands have been drying and 32% have been wetting over this period, illustrating the complex ecohydrological dynamics of high latitude peatlands and their highly uncertain responses to a warming climate. Abstract
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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.
Qin Y, Li H, Mazei Y, Kurina I, Swindles GT, Bobrov A, Tsyganov AN, Gu Y, Huang X, Xue J, et al
(2021). Developing a continental-scale testate amoeba hydrological transfer function for Asian peatlands. Quaternary Science Reviews
Developing a continental-scale testate amoeba hydrological transfer function for Asian peatlands
Testate amoebae (TA) are a common and diverse group of protists and are especially abundant in peatlands. The structure of peatland TA communities is well correlated to surface moisture and water table depth (WTD). For that reason, TA are widely used as proxy indicators in ecological and palaeoecological studies. Peatlands are abundant across Asia, but the diversity and ecology of the TA that inhabit these systems are poorly documented. It is therefore unclear whether TA can be used as palaeohydrological indicators in the manner in which they commonly are in Europe and North-America. There is particular uncertainty as to the efficacy of this approach in the lower latitudes. We compiled existing and new data on testate amoebae from 1124 Sphagnum-dominated samples from 42 individual peatlands covering broad latitudinal (25°–66° N) and longitudinal (68°–129° E) ranges. Using a consensus taxonomic framework, we built a checklist of TA and developed TA-based hydrological transfer functions for Asian peatlands. The results showed that three models, weighted averaging (WA), weighted average partial least squares (WA-PLS), and maximum likelihood (ML), predicted similar WTD values for full samples, while the modern analogue technique (MAT) produced the strongest (R2boot = 0.58) relationship between observed and estimated water-table depths (WTDs). Removing outlier samples improved the R2 values of observed vs. estimated WTDs, with ML then demonstrating the strongest predictive power (R2boot = 0.68, RMSEPboot = 8.98 cm). The predictive capability of the developed WTD transfer function is comparable to equivalent models for Europe and North America and thus can be used for palaeohydrological reconstructions for boreal to subtropical peatlands in Asia. Abstract
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
Divergent responses of permafrost peatlands to recent climate change
. 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.
León CA, Gabriel M, Rodríguez C, Iturraspe R, Savoretti A, Pancotto V, Benítez-Mora A, Valdés A, Díaz MF, Oberpaur C, et al
(2021). Peatlands of southern south america: a review. Mires and Peat
Peatlands of southern south america: a review
Southern South American peatlands (SSAP) play a key role in the ecological dynamics of Patagonia. They mostly comprise of undisturbed environments which provide important ecosystem services, including carbon sequestration, water reservoir and habitat for both widespread and endemic organisms. When compared with boreal peatlands, our knowledge of the functioning of SSAP is poor, and it is necessary to raise awareness about their scientific and ecological value and to ensure their conservation. This article examines a broad base of historical and contemporary published research literature on the peatlands of Chile and Argentina, from 1843 onwards, to identify gaps in knowledge, implications for the assessment of peatland functioning, and targets for peatland conservation and management. To achieve this goal, we reviewed a total of 196 research papers/reports from across the peer-reviewed and grey literature. We conclude that gaps in our knowledge and understanding of SSAP have deeply undermined the development of effective conservation strategies for these understudied ecosystems. To reverse this situation, we recommend that future research and management efforts should aim: (1) to build an inventory of the peatlands that exist in SSAP, including their location and area; (2) to ensure land use planning prioritises the maintenance of SSAP ecosystem services; (3) to improve existing legislation and protocols of good and sustainable practice for extractive activities; and (4) to carry out an extensive awareness campaign aimed at the local population and key decision makers. Abstract
McKeown MM, Mitchell EAD, Amesbury MJ, Blandenier Q, Charman D, Duckert C, Roland TP, Swindles GT, Wood JR, Wilmshurst JM, et al (2021). The testate amoebae of New Zealand: a checklist, identification key and assessment of biogeographic patterns. European Journal of Protistology, 81, 125789-125789.
LI C, Sonke J, Le Roux G, Piotrowska N, Van der Putten N, Roberts S, Daley T, Rice E, Gehrels R, Enrico M, et al (2021). Unequal Anthropogenic Enrichment of Mercury in Earth’s Northernand Southern Hemispheres. Goldschmidt2021 abstracts.
Zhang H, Väliranta M, Piilo S, Amesbury MJ, Aquino-López MA, Roland TP, Salminen-Paatero S, Paatero J, Lohila A, Tuittila E-S, et al
(2020). Decreased carbon accumulation feedback driven by climate-induced drying of two southern boreal bogs over recent centuries. Glob Chang Biol
Decreased carbon accumulation feedback driven by climate-induced drying of two southern boreal bogs over recent centuries.
Northern boreal peatlands are important ecosystems in modulating global biogeochemical cycles, yet their biological communities and related carbon dynamics are highly sensitive to changes in climate. Despite this, the strength and recent direction of these feedbacks are still unclear. The response of boreal peatlands to climate warming has received relatively little attention compared with other northern peatland types, despite forming a large northern hemisphere-wide ecosystem. Here, we studied the response of two ombrotrophic boreal peatlands to climate variability over the last c. 200 years for which local meteorological data are available. We used remains from plants and testate amoebae to study historical changes in peatland biological communities. These data were supplemented by peat property (bulk density, carbon and nitrogen content), 14 C, 210 Pb and 137 Cs analyses and were used to infer changes in peatland hydrology and carbon dynamics. In total, six peat cores, three per study site, were studied that represent different microhabitats: low hummock (LH), high lawn and low lawn. The data show a consistent drying trend over recent centuries, represented mainly as a change from wet habitat Sphagnum spp. to dry habitat S. fuscum. Summer temperature and precipitation appeared to be important drivers shaping peatland community and surface moisture conditions. Data from the driest microhabitat studied, LH, revealed a clear and strong negative linear correlation (R2 = .5031; p Abstract
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Swindles GT, Roland TP, Amesbury MJ, Lamentowicz M, McKeown MM, Sim TG, Fewster RE, Mitchell EAD (2020). Quantifying the effect of testate amoeba decomposition on peat-based water-table reconstructions. European Journal of Protistology, 74, 125693-125693.
Li C, Sonke JE, Le Roux G, Piotrowska N, Van Der Putten N, Roberts SJ, Daley T, Rice E, Gehrels R, Enrico M, et al
(2020). Unequal Anthropogenic Enrichment of Mercury in Earth's Northern and Southern Hemispheres. ACS Earth and Space Chemistry
Unequal Anthropogenic Enrichment of Mercury in Earth's Northern and Southern Hemispheres
Remote Northern Hemisphere (NH) and Southern Hemisphere (SH) lake sediment and peat records of mercury (Hg) deposition have shown a ×3 to ×5 Hg enrichment since pre-industrial times ( Abstract
McKeown MM, Caseldine CJ, Thompson G, Swindles GT, Ivanovic RF, Roland TP, Valdes PJ, Potito AP (2019). Complexities in interpreting chironomid-based temperature reconstructions over the Holocene from a lake in Western Ireland. Quaternary Science Reviews, 222, 105908-105908.
Newnham RM, Hazell ZJ, Charman DJ, Lowe DJ, Rees ABH, Amesbury MJ, Roland TP, Gehrels M, van den Bos V, Jara IA, et al
(2019). Peat humification records from Restionaceae bogs in northern New Zealand as potential indicators of Holocene precipitation, seasonality, and ENSO. Quaternary Science Reviews
Peat humification records from Restionaceae bogs in northern New Zealand as potential indicators of Holocene precipitation, seasonality, and ENSO
In comparison with temperature reconstructions, New Zealand proxy records for paleo-precipitation are rare, despite the importance of precipitation in contemporary climate variability and for projected climate impacts. In this study, records of mid-late Holocene palaeomoisture variation were derived for two hydrologically separate ombrotrophic Restionaceae bogs in northern New Zealand, based on peat humification analysis. At each site, three cores were analysed for peat humification, facilitating both intra- and inter-site comparisons. Age models for the six sequences were developed using radiocarbon dating and tephrochronology. Twelve tephras (including six cryptotephras) were recognised, four of which were used to precisely link the two sites and to define start and end points for the records at 7027 ± 170 (Tuhua tephra) and 1718 ± 10 cal yr BP (Taupo tephra) (2σ-age ranges), respectively. We find individual differences between the six peat humification records at short-term timescales that are presumably due to local site factors, in particular changing vegetation and microtopography, or to changes in the composition of the material analysed. Stronger longer-term coherence is observed between all six records but is attributed to slow anaerobic decay over time because the implied trend towards wetter summers in the late Holocene cannot be corroborated by independent climate proxies. Despite these confounding factors, centennial scale shifts in bog surface wetness are a pervasive feature of all six records with varying degrees of overlap in time that show strong correspondence with El Niño-Southern Oscillation reconstructions from the eastern equatorial Pacific. These results indicate the potential for peat humification records from New Zealand's ombrotrophic bogs to elucidate past climate variability and also demonstrate the importance of developing multiple well-dated profiles from more than one site. 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.
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.
Amesbury MJ, Booth RK, Roland TP, Bunbury J, Clifford MJ, Charman DJ, Elliot S, Finkelstein S, Garneau M, Hughes PDM, et al
(2018). Towards a Holarctic synthesis of peatland testate amoeba ecology: Development of a new continental-scale palaeohydrological transfer function for North America and comparison to European data. Quaternary Science Reviews
Towards a Holarctic synthesis of peatland testate amoeba ecology: Development of a new continental-scale palaeohydrological transfer function for North America and comparison to European data
Fossil testate amoeba assemblages have been used to reconstruct peatland palaeohydrology for more than two decades. While transfer function training sets are typically of local-to regional-scale in extent, combining those data to cover broad ecohydrological gradients, from the regional-to continental- and hemispheric-scales, is useful to assess if ecological optima of species vary geographically and therefore may have also varied over time. Continental-scale transfer functions can also maximise modern analogue quality without losing reconstructive skill, providing the opportunity to contextualise understanding of purely statistical outputs with greater insight into the biogeography of organisms. Here, we compiled, at moderate taxonomic resolution, a dataset of nearly 2000 modern surface peatland testate amoeba samples from 137 peatlands throughout North America. We developed transfer functions using four model types, tested them statistically and applied them to independent palaeoenvironmental data. By subdividing the dataset into eco-regions, we examined biogeographical patterns of hydrological optima and species distribution across North America. We combined our new dataset with data from Europe to create a combined transfer function. The performance of our North-American transfer function was equivalent to published models and reconstructions were comparable to those developed using regional training sets. The new model can therefore be used as an effective tool to reconstruct peatland palaeohydrology throughout the North American continent. Some eco-regions exhibited lower taxonomic diversity and some key indicator taxa had restricted ranges. However, these patterns occurred against a background of general cosmopolitanism, at the moderate taxonomic resolution used. Likely biogeographical patterns at higher taxonomic resolution therefore do not affect transfer function performance. Output from the combined North American and European model suggested that any geographical limit of scale beyond which further compilation of peatland testate amoeba data would not be valid has not yet been reached, therefore advocating the potential for a Holarctic synthesis of peatland testate amoeba data. Extending data synthesis to the tropics and the Southern Hemisphere would be more challenging due to higher regional endemism in those areas. Abstract
van Bellen S, Mauquoy D, Payne RJ, Roland TP, Hughes PDM, Daley TJ, Loader NJ, Street-Perrott FA, Rice EM, Pancotto VA, et al
(2017). An alternative approach to transfer functions? Testing the performance of a functional trait-based model for testate amoebae. PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
, 173-183. Author URL
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 Biology
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
Roland TP, Amesbury MJ, Wilkinson DM, Charman DJ, Convey P, Hodgson DA, Royles J, Clauß S, Völcker E
(2017). Taxonomic Implications of Morphological Complexity Within the Testate Amoeba Genus Corythion from the Antarctic Peninsula. Protist
Taxonomic Implications of Morphological Complexity Within the Testate Amoeba Genus Corythion from the Antarctic Peninsula.
Precise and sufficiently detailed morphological taxonomy is vital in biology, for example in the accurate interpretation of ecological and palaeoecological datasets, especially in polar regions, where biodiversity is poor. Testate amoebae on the Antarctic Peninsula (AP) are well-documented and variations in their population size have recently been interpreted as a proxy for microbial productivity changes in response to recent regional climate change. AP testate amoeba assemblages are dominated by a small number of globally ubiquitous taxa. We examine morphological variation in Corythion spp. across the AP, finding clear evidence supporting the presence of two morphospecies. Corythion constricta (Certes 1889) was identified on the AP for the first time and has potentially been previously misidentified. Furthermore, a southerly trend of decreasing average test size in Corythion dubium (Taránek 1881) along the AP suggests adaptive polymorphism, although the precise drivers of this remain unclear, with analysis hindered by limited environmental data. Further work into morphological variation in Corythion is needed elsewhere, alongside molecular analyses, to evaluate the potential for (pseudo)cryptic diversity within the genus. We advocate a parsimonious taxonomical approach that recognises genetic diversity but also examines and develops accurate morphological divisions and descriptions suitable for light microscopy-based ecological and palaeoecological studies. Abstract
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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
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
Amesbury MJ, Roland TP, Royles J, Hodgson DA, Convey P, Griffiths H, Charman DJ
(2017). Widespread Biological Response to Rapid Warming on the Antarctic Peninsula. Curr Biol
Widespread Biological Response to Rapid Warming on the Antarctic Peninsula.
Recent climate change on the Antarctic Peninsula is well documented [1-5], with warming, alongside increases in precipitation, wind strength, and melt season length [1, 6, 7], driving environmental change [8, 9]. However, meteorological records mostly began in the 1950s, and paleoenvironmental datasets that provide a longer-term context to recent climate change are limited in number and often from single sites  and/or discontinuous in time [10, 11]. Here we use moss bank cores from a 600-km transect from Green Island (65.3°S) to Elephant Island (61.1°S) as paleoclimate archives sensitive to regional temperature change, moderated by water availability and surface microclimate [12, 13]. Mosses grow slowly, but cold temperatures minimize decomposition, facilitating multi-proxy analysis of preserved peat . Carbon isotope discrimination (Δ13C) in cellulose indicates the favorability of conditions for photosynthesis . Testate amoebae are representative heterotrophs in peatlands [16-18], so their populations are an indicator of microbial productivity . Moss growth and mass accumulation rates represent the balance between growth and decomposition . Analyzing these proxies in five cores at three sites over 150 years reveals increased biological activity over the past ca. 50 years, in response to climate change. We identified significant changepoints in all sites and proxies, suggesting fundamental and widespread changes in the terrestrial biosphere. The regional sensitivity of moss growth to past temperature rises suggests that terrestrial ecosystems will alter rapidly under future warming, leading to major changes in the biology and landscape of this iconic region-an Antarctic greening to parallel well-established observations in the Arctic . Abstract
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Amesbury MJ, Swindles GT, Bobrov A, Charman DJ, Holden J, Lamentowicz M, Mallon G, Mazei Y, Mitchell EAD, Payne RJ, et al
(2016). Development of a new pan-European testate amoeba transfer function for reconstructing peatland palaeohydrology. Quaternary Science Reviews
Development of a new pan-European testate amoeba transfer function for reconstructing peatland palaeohydrology
In the decade since the first pan-European testate amoeba-based transfer function for peatland palaeohydrological reconstruction was published, a vast amount of additional data collection has been undertaken by the research community. Here, we expand the pan-European dataset from 128 to 1799 samples, spanning 35° of latitude and 55° of longitude. After the development of a new taxonomic scheme to permit compilation of data from a wide range of contributors and the removal of samples with high pH values, we developed ecological transfer functions using a range of model types and a dataset of ∼1300 samples. We rigorously tested the efficacy of these models using both statistical validation and independent test sets with associated instrumental data. Model performance measured by statistical indicators was comparable to other published models. Comparison to test sets showed that taxonomic resolution did not impair model performance and that the new pan-European model can therefore be used as an effective tool for palaeohydrological reconstruction. Our results question the efficacy of relying on statistical validation of transfer functions alone and support a multi-faceted approach to the assessment of new models. We substantiated recent advice that model outputs should be standardised and presented as residual values in order to focus interpretation on secure directional shifts, avoiding potentially inaccurate conclusions relating to specific water-table depths. The extent and diversity of the dataset highlighted that, at the taxonomic resolution applied, a majority of taxa had broad geographic distributions, though some morphotypes appeared to have restricted ranges. Abstract
van Bellen S, Mauquoy D, Hughes PDM, Roland TP, Daley TJ, Loader NJ, Street-Perrott FA, Rice EM, Pancotto VA, Payne RJ, et al
(2016). Late-Holocene climate dynamics recorded in the peat bogs of Tierra del Fuego, South America. HOLOCENE
(3), 489-501. Author URL
Loader NJ, Street-Perrott FA, Mauquoy D, Roland TP, van Bellen S, Daley TJ, Davies D, Hughes PDM, Pancotto VO, Young GHF, et al
(2016). Measurements of hydrogen, oxygen and carbon isotope variability in Sphagnum moss along a micro-topographical gradient in a southern Patagonian peatland. Journal of Quaternary Science
Measurements of hydrogen, oxygen and carbon isotope variability in Sphagnum moss along a micro-topographical gradient in a southern Patagonian peatland
Peat archives offer a diverse range of physical and chemical proxies from which it is possible to study past environmental and ecological changes. Direct numerical calibration and verification is difficult so process-based and mechanistic studies are therefore required to establish and quantify links between environmental changes and their associated proxy-responses. Traditional ‘space-for-time’ calibrations provide a solution to this calibration problem, but are often unable to isolate a single environmental variable from other potentially confounding variables. In this study, we explored the potential of a site-specific ‘space-for-time’ approach applied to a hummock-hollow transect on an ombrotrophic raised bog in Patagonia, southern Chile. Coupled stable carbon, oxygen and hydrogen isotopic measurements were made on individual samples of Sphagnum moss cellulose and compared with plant-associated waters, local hydrology, temperature and relative humidity, sampled at the same points along the study transect. Results reveal a range of environmental responses, which were supported by plant-physiological models in the case of carbon and oxygen isotopes. For hydrogen isotopes, the results obtained from cellulose indicated a need for further research into hydrogen isotope fractionation in Sphagnum. We recommend conducting site-specific characterization of plant response to support the development of peat-based isotope records for palaeoenvironmental research, and where logistically possible, that monitoring is conducted over timescales appropriate to the time-integrative nature of the Sphagnum record. Abstract
Royles J, Amesbury MJ, Roland TP, Jones GD, Convey P, Griffiths H, Hodgson DA, Charman DJ
(2016). Moss stable isotopes (carbon-13, oxygen-18) and testate amoebae reflect environmental inputs and microclimate along a latitudinal gradient on the Antarctic Peninsula. Oecologia
Moss stable isotopes (carbon-13, oxygen-18) and testate amoebae reflect environmental inputs and microclimate along a latitudinal gradient on the Antarctic Peninsula.
The stable isotope compositions of moss tissue water (δ(2)H and δ(18)O) and cellulose (δ(13)C and δ(18)O), and testate amoebae populations were sampled from 61 contemporary surface samples along a 600-km latitudinal gradient of the Antarctic Peninsula (AP) to provide a spatial record of environmental change. The isotopic composition of moss tissue water represented an annually integrated precipitation signal with the expected isotopic depletion with increasing latitude. There was a weak, but significant, relationship between cellulose δ(18)O and latitude, with predicted source water inputs isotopically enriched compared to measured precipitation. Cellulose δ(13)C values were dependent on moss species and water content, and may reflect site exposure to strong winds. Testate amoebae assemblages were characterised by low concentrations and taxonomic diversity, with Corythion dubium and Microcorycia radiata types the most cosmopolitan taxa. The similarity between the intra- and inter-site ranges measured in all proxies suggests that microclimate and micro-topographical conditions around the moss surface were important determinants of proxy values. Isotope and testate amoebae analyses have proven value as palaeoclimatic, temporal proxies of climate change, whereas this study demonstrates that variations in isotopic and amoeboid proxies between microsites can be beyond the bounds of the current spatial variability in AP climate. Abstract
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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
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
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
Swindles GT, Amesbury MJ, Turner TE, Carrivick JL, Woulds C, Raby C, Mullan D, Roland TP, Galloway JM, Parry L, et al
(2015). Evaluating the use of testate amoebae for palaeohydrological reconstruction in permafrost peatlands. Palaeogeography, Palaeoclimatology, Palaeoecology
Evaluating the use of testate amoebae for palaeohydrological reconstruction in permafrost peatlands
The melting of high-latitude permafrost peatlands is a major concern due to a potential positive feedback on global climate change. We examine the ecology of testate amoebae in permafrost peatlands, based on sites in Sweden (~200km north of the Arctic Circle). Multivariate statistical analysis confirms that water-table depth and moisture content are the dominant controls on the distribution of testate amoebae, corroborating the results from studies in mid-latitude peatlands. We present a new testate amoeba-based water table transfer function and thoroughly test it for the effects of spatial autocorrelation, clustered sampling design and uneven sampling gradients. We find that the transfer function has good predictive power; the best-performing model is based on tolerance-downweighted weighted averaging with inverse deshrinking (performance statistics with leave-one-out cross validation: R2=0.87, RMSEP=5.25cm). The new transfer function was applied to a short core from Stordalen mire, and reveals a major shift in peatland ecohydrology coincident with the onset of the Little Ice Age (c. AD 1400). We also applied the model to an independent contemporary dataset from Stordalen and find that it outperforms predictions based on other published transfer functions. The new transfer function will enable palaeohydrological reconstruction from permafrost peatlands in Northern Europe, thereby permitting greatly improved understanding of the long-term ecohydrological dynamics of these important carbon stores as well as their responses to recent climate change. Abstract
Loader NJ, Street-Perrott FA, Daley TJ, Hughes PDM, Kimak A, Levanič T, Mallon G, Mauquoy D, Robertson I, Roland TP, et al
(2015). Simultaneous determination of stable carbon, oxygen, and hydrogen isotopes in cellulose. Analytical Chemistry
Simultaneous determination of stable carbon, oxygen, and hydrogen isotopes in cellulose
A technological development is described through which the stable carbon-, oxygen-, and nonexchangeable hydrogen-isotopic ratios (δ13C, δ18O, δ2H) are determined on a single carbohydrate (cellulose) sample with precision equivalent to conventional techniques (δ13C 0.15‰, δ18O 0.30‰, δ2H 3.0‰). This triple-isotope approach offers significant new research opportunities, most notably in physiology and medicine, isotope biogeochemistry, forensic science, and palaeoclimatology, when isotopic analysis of a common sample is desirable or when sample material is limited. Abstract
Roland TP, Mackay H, Hughes PDM
(2015). Tephra analysis in ombrotrophic peatlands: a geochemical comparison of acid digestion and density separation techniques. JOURNAL OF QUATERNARY SCIENCE
(1), 3-8. Author URL
Roland TP, Daley TJ, Caseldine CJ, Charman DJ, Turney CSM, Amesbury MJ, Thompson GJ, Woodley EJ
(2015). The 5.2 ka climate event: Evidence from stable isotope and multi-proxy palaeoecological peatland records in Ireland. Quaternary Science Reviews
The 5.2 ka climate event: Evidence from stable isotope and multi-proxy palaeoecological peatland records in Ireland
Evidence for a major climate event at 5.2 ka has been reported globally and is associated with considerable societal disruption, but is poorly characterised in northwest Europe. This event forms part of a broader period of re-organisation in the Earth's ocean-atmosphere circulation system between 6 and 5 ka. This study tests the nature and timing of the event in northwest Europe, a region highly sensitive to change in meridional overturning circulation and mid-latitude westerly airflow. Here we report three high-resolution Irish multi-proxy records obtained from ombrotrophic peatlands that have robust chronological frameworks. We identify the 5.2 ka event by a sustained decrease in δ18Ocellulose at all three sites, with additional and parallel changes in δ13Ccellulose and palaeoecological (testate amoebae, plant macrofossil and humification) data from two sites in northern Ireland. Data from Sluggan Moss demonstrate a particularly coherent shift towards wetter conditions. These data support the hypothesis that the event was caused by a prolonged period of positive North Atlantic Oscillation conditions, resulting in pervasive cyclonic weather patterns across northwest Europe, increasing precipitation over Ireland. 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
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
De Vleeschouwer F, Vanneste H, Mauquoy D, Piotrowska N, Torrejón F, Roland TP, Stein A, Le Roux G
(2014). Emissions from Pre-Hispanic Metallurgy in the South American Atmosphere. PLoS One
(9). Author URL
Seddon AWR, Mackay AW, Baker AG, Birks HJB, Breman E, Buck CE, Ellis EC, Froyd CA, Gill JL, Gillson L, et al
(2014). Looking forward through the past: Identification of 50 priority research questions in palaeoecology. Journal of Ecology
Looking forward through the past: Identification of 50 priority research questions in palaeoecology
Priority question exercises are becoming an increasingly common tool to frame future agendas in conservation and ecological science. They are an effective way to identify research foci that advance the field and that also have high policy and conservation relevance. To date, there has been no coherent synthesis of key questions and priority research areas for palaeoecology, which combines biological, geochemical and molecular techniques in order to reconstruct past ecological and environmental systems on time-scales from decades to millions of years. We adapted a well-established methodology to identify 50 priority research questions in palaeoecology. Using a set of criteria designed to identify realistic and achievable research goals, we selected questions from a pool submitted by the international palaeoecology research community and relevant policy practitioners. The integration of online participation, both before and during the workshop, increased international engagement in question selection. The questions selected are structured around six themes: human-environment interactions in the Anthropocene; biodiversity, conservation and novel ecosystems; biodiversity over long time-scales; ecosystem processes and biogeochemical cycling; comparing, combining and synthesizing information from multiple records; and new developments in palaeoecology. Future opportunities in palaeoecology are related to improved incorporation of uncertainty into reconstructions, an enhanced understanding of ecological and evolutionary dynamics and processes and the continued application of long-term data for better-informed landscape management. © 2013 the Authors. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Abstract
Hughes PDM, Roland TP, Mauquoy D (2014). Peatlands and carbon credits: natural and anthropogenic threats to the carbon stock. Carbon Management
Van Bellen S, Mauquoy D, Payne RJ, Roland TP, Daley TJ, Hughes PDM, Loader NJ, Street-Perrott FA, Rice EM, Pancotto VA, et al
(2014). Testate amoebae as a proxy for reconstructing Holocene water table dynamics in southern Patagonian peat bogs. Journal of Quaternary Science
Testate amoebae as a proxy for reconstructing Holocene water table dynamics in southern Patagonian peat bogs
Testate amoebae are abundant and diverse in Sphagnum peat bogs and have been used extensively as indicators of past water table depths. Although these unicellular protists are widely dispersed with globally similar hydrological preferences, regional variations in communities demand region-specific transfer functions. Here we present the first transfer function for southern Patagonian bogs, based on 154 surface samples obtained from transects in five bogs sampled in 2012 and 2013. Significant variance was explained by pH, electrical conductivity and, in particular, water table depth. Transfer functions for water table were constructed using weighted averaging and evaluated by cross-validation and independent test sets. The optimal transfer function has predictive ability, but relatively high prediction errors given the wide range in sampled water tables. The use of independent test sets, as well as cross-validation, allows a more rigorous assessment of model performance than most previous studies. For a subset of locations we compare surface and subsurface samples to demonstrate significant differences in community composition, possibly due to vertical zonation. Our results provide the first quantification of hydrological optima and tolerances for several rare species, which may include Southern Hemisphere endemics and pave the way for palaeohydrological reconstructions in southern Patagonian bogs. © 2014 John Wiley & Sons, Ltd. Abstract
Roland TP, Caseldine CJ, Charman DJ, Turney CSM, Amesbury MJ
(2014). Was there a '4.2ka event' in Great Britain and Ireland? Evidence from the peatland record. Quaternary Science Reviews
Was there a '4.2ka event' in Great Britain and Ireland? Evidence from the peatland record
Palaeoenvironmental and archaeological data from several regions around the world show evidence of a multi-centennial climatic event occurring approximately 4200cal yr BP (4.2ka). Whilst the climatic change and/or impact of the 4.2ka event is clear in certain regions, such as western Asia, evidence for the event has yet to be fully evaluated in northwest Europe. This study presents high-resolution, multi-proxy palaeoclimate records from sites in Northern Ireland, ideally located for an objective examination of the nature of the event in Great Britain and Ireland within the broader context of mid-Holocene climate change c. 6.5-2.5ka. The peatlands of northwest Europe possess considerable potential for the examination of climatic change in the North Atlantic region, demonstrated by the range of palaeohydrological proxy data generated during this study (peat humification, plant macrofossil and testate amoebae analyses) supported by a high-resolution chronology (including comprehensive AMS 14C and tephrochronology). The inter-site testate amoebae reconstructions appear coherent and were combined to produce a regional climatic record, in marked contrast to the plant macrofossil and peat humification records that appear climatically complacent. The testate amoebae reconstruction, however, provides no compelling evidence for a 4.2ka event signal and is consistent with previously reported studies from across northwest Europe, suggesting the origin and impact of this event is spatially complex. © 2013 Elsevier Ltd. Abstract
Swindles GT, Lawson IT, Matthews IP, Blaauw M, Daley TJ, Charman DJ, Roland TP, Plunkett G, Schettler G, Gearey BR, et al
(2013). Centennial-scale climate change in Ireland during the Holocene. Earth-Science Reviews
Centennial-scale climate change in Ireland during the Holocene
We examine mid- to late Holocene centennial-scale climate variability in Ireland using proxy data from peatlands, lakes and a speleothem. A high degree of between-record variability is apparent in the proxy data and significant chronological uncertainties are present. However, tephra layers provide a robust tool for correlation and improve the chronological precision of the records. Although we can find no statistically significant coherence in the dataset as a whole, a selection of high-quality peatland water table reconstructions co-vary more than would be expected by chance alone. A locally weighted regression model with bootstrapping can be used to construct a 'best-estimate' palaeoclimatic reconstruction from these datasets. Visual comparison and cross-wavelet analysis of peatland water table compilations from Ireland and Northern Britain show that there are some periods of coherence between these records. Some terrestrial palaeoclimatic changes in Ireland appear to coincide with changes in the North Atlantic thermohaline circulation and solar activity. However, these relationships are inconsistent and may be obscured by chronological uncertainties. We conclude by suggesting an agenda for future Holocene climate research in Ireland. © 2013 Elsevier B.V. Abstract
(2013). Letters from patagonia. Planet Earth
Letters from patagonia
Tom Roland describes weeks tramping through the bogs of Tierra del Fuego in an effort to redress the balance. Patagonia has always held a mysterious fascination for explorers, travelers and those following la ruta del fin del mundo - the road to the end of the world. It was not just Darwin Tom would be following, but Ferdinand Magellan, Bruce Chatwin and any number of hopeful nineteenth-century gold prospectors. Thirty-six hours, four flights and over 8000 miles later, Tom find himself squelching across some of the world's most pristine peatlands. The snow-capped Southern Andes rise steeply on either side, and the bright red Sphagnum magellanicum, the moss species so characteristic of these bogs, contrasts sharply with the blue sky of an unseasonably warm austral summer. Peatlands occupy about three per cent of the Earth's land surface, but this distribution is heavily skewed towards the north. Abstract
Daley TJ, Mauquoy D, Chambers FM, Street-Perrott FA, Hughes PDM, Loader NJ, Roland TP, Van Bellen S, Garcia-Meneses P, Lewin S, et al
(2012). Investigating late Holocene variations in hydroclimate and the stable isotope composition of precipitation using southern South American peatlands: an hypothesis. Climate of the Past
Investigating late Holocene variations in hydroclimate and the stable isotope composition of precipitation using southern South American peatlands: an hypothesis
Ombrotrophic raised peatlands provide an ideal archive for integrating late Holocene records of variations in hydroclimate and the estimated stable isotope composition of precipitation with recent instrumental measurements. Modern measurements of mean monthly surface air temperature, precipitation, and δD and δ18O-values in precipitation from the late twentieth and early twenty-first centuries provide a short but invaluable record with which to investigate modern relationships between these variables, thereby enabling improved interpretation of the peatland palaeodata. Stable isotope data from two stations in the Global Network for Isotopes in Precipitation (GNIP) from southern South America (Punta Arenas, Chile and Ushuaia, Argentina) were analysed for the period 1982 to 2008 and compared with longer-term meteorological data from the same locations (1890 to present and 1931 to present, respectively). δD and δ18O-values in precipitation have exhibited quite different trends in response to local surface air temperature and precipitation amount. At Punta Arenas, there has been a marked increase in the seasonal difference between summer and winter δ18O-values. A decline in the deuterium excess of summer precipitation at this station was associated with a general increase in relative humidity at 1000 mb over the surface of the Southeast Pacific Ocean, believed to be the major vapour source for the local precipitation. At Ushuaia, a fall in δ18O-values was associated with an increase in the mean annual amount of precipitation. Both records are consistent with a southward retraction and increase in zonal wind speed of the austral westerly wind belt. These regional differences, observed in response to a known driver, should be detectable in peatland sites close to the GNIP stations. Currently, insufficient data with suitable temporal resolution are available to test for these regional differences over the last 3000 yr. Existing peatland palaeoclimate data from two sites near Ushuaia, however, provide evidence for changes in the late Holocene that are consistent with the pattern observed in modern observations. © Author(s) 2012. Abstract
Roland TP (2012). The ‘4.2 kyr event’ in the British Isles: evidence for an abrupt climate event in the North Atlantic?. Quaternary International, 279
Fyfe RM, Brück J, Johnston R, Lewis H, Roland TP, Wickstead H
(2008). Historical context and chronology of Bronze Age land enclosure on Dartmoor, UK. Journal of Archaeological Science
Historical context and chronology of Bronze Age land enclosure on Dartmoor, UK
The upland of Dartmoor, southwest England, is one of the flagship prehistoric landscapes within Britain owing to the excellent survival of extensive prehistoric coaxial field systems. Archaeological surveys and rescue excavations during the 1970s and 1980s did much to further the understanding of this landscape; however, much remains to be explored, in particular the chronology of enclosure, the nature of the pre-enclosure landscape and the relationship between Bronze Age communities and their environment. Reconsideration of this landscape is important, given the place it holds in our understanding of subdivision of the landscape across northwest Europe during prehistory. This paper presents new palaeoecological data recovered as part of an integrated archaeological and palaeoecological project on northeast Dartmoor. The sequences detailed here include the first dated Neolithic period palaeoenvironmental data from within the prehistoric enclosed land on the moor, providing a longer-term context for enclosure. Neolithic groups are implicated in the first establishment of heathland in the study area at around 3630-3370 cal BC. During the early Bronze Age, reestablishment of hazel scrub in the study area implies reduced use of the upland, although it is not clear whether this is local or indicative of the wider landscape. A combination of pollen and fungal spore data indicates a substantial shift to species-rich grassland with grazing animals at c.1480 cal BC in a phase that lasted 400 years. The later Bronze Age and early Iron Age are characterised by low intensity use of the upland. These data provide new chronological data for land cover change on Dartmoor and whilst they broadly confirm existing models of upland land use in later prehistory, their proximity to the standing archaeology affords a more nuanced interpretation of local change. © 2008 Elsevier Ltd. All rights reserved. Abstract