| 1. |
- Sim, Thomas G., et al.
(författare)
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Regional variability in peatland burning at mid-to high-latitudes during the Holocene
- 2023
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Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 305
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Tidskriftsartikel (refereegranskat)abstract
- Northern peatlands store globally-important amounts of carbon in the form of partly decomposed plant detritus. Drying associated with climate and land-use change may lead to increased fire frequency and severity in peatlands and the rapid loss of carbon to the atmosphere. However, our understanding of the patterns and drivers of peatland burning on an appropriate decadal to millennial timescale relies heavily on individual site-based reconstructions. For the first time, we synthesise peatland macrocharcoal re-cords from across North America, Europe, and Patagonia to reveal regional variation in peatland burning during the Holocene. We used an existing database of proximal sedimentary charcoal to represent regional burning trends in the wider landscape for each region. Long-term trends in peatland burning appear to be largely climate driven, with human activities likely having an increasing influence in the late Holocene. Warmer conditions during the Holocene Thermal Maximum (similar to 9e6 cal. ka BP) were associated with greater peatland burning in North America's Atlantic coast, southern Scandinavia and the Baltics, and Patagonia. Since the Little Ice Age, peatland burning has declined across North America and in some areas of Europe. This decline is mirrored by a decrease in wider landscape burning in some, but not all sub-regions, linked to fire-suppression policies, and landscape fragmentation caused by agricultural expansion. Peatlands demonstrate lower susceptibility to burning than the wider landscape in several instances, probably because of autogenic processes that maintain high levels of near-surface wetness even during drought. Nonetheless, widespread drying and degradation of peatlands, particularly in Europe, has likely increased their vulnerability to burning in recent centuries. Consequently, peatland restoration efforts are important to mitigate the risk of peatland fire under a changing climate. Finally, we make recommendations for future research to improve our understanding of the controls on peatland fires.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 2. |
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| 3. |
- Blaauw, Maarten, et al.
(författare)
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Testing the timing of radiocarbon-dated events between proxy archives
- 2007
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 17:2, s. 283-288
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Tidskriftsartikel (refereegranskat)abstract
- For interpreting past changes on a regional or global scale, the timings of proxy-inferred events are usually aligned with data from other locations. However, too often chronological uncertainties are ignored in proxy diagrams and multisite comparisons, making it possible for researchers to fall into the trap of sucking separate events into one illusionary event (or vice versa). Here we largely solve this ‘suck in and smear syndrome’ for radiocarbon (14C) dated sequences. In a Bayesian framework, millions of plausible age-models are constructed to quantify the chronological uncertainties within and between proxy archives. We test the technique on replicated high-resolution 14C-dated peat cores deposited during the ‘Little Ice Age’ (c. AD 1400-1900), a period characterized by abrupt climate changes and severe 14C calibration problems. Owing to internal variability in proxy data and uncertainties in age-models, these (and possibly many more) archives are not consistent in recording decadal climate change. Through explicit statistical tests of palaeoenvironmental hypotheses, we can move forward to systematic interpretations of proxy data. However, chronological uncertainties of non-annually resolved palaeoclimate records are too large for answering decadal timescale questions.
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| 4. |
- Chambers, Frank, et al.
(författare)
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Globally synchronous climate change 2800 years ago: proxy data from peat in South America
- 2007
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X .- 1385-013X. ; 253:3-4, s. 439-444
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Tidskriftsartikel (refereegranskat)abstract
- Initial findings from high-latitude ice-cores implied a relatively unvarying Holocene climate, in contrast to the major climate swings in the preceding late-Pleistocene. However, several climate archives from low latitudes imply a less than equable Holocene climate, as do recent studies on peat bogs in mainland north-west Europe, which indicate an abrupt climate cooling 2800 years ago, with parallels claimed in a range of climate archives elsewhere. A hypothesis that this claimed climate shift was global, and caused by reduced solar activity, has recently been disputed. Until now, no directly comparable data were available from the southern hemisphere to help resolve the dispute. Building on investigations of the vegetation history of an extensive mire in the Valle de Andorra, Tierra del Fuego, we took a further peat core from the bog to generate a high-resolution climate history through the use of determination of peat humification and quantitative leaf-count plant macrofossil analysis. Here, we present the new proxy-climate data from the bog in South America. The data are directly comparable with those in Europe, as they were produced using identical laboratory methods. They show that there was a major climate perturbation at the same time as in northwest European bogs. Its timing, nature and apparent global synchronicity lend support to the notion of solar forcing of past climate change, amplified by oceanic circulation. This finding of a similar response simultaneously in both hemispheres may help validate and improve global climate models. That reduced solar activity might cause a global climatic change suggests that attention be paid also to consideration of any global climate response to increases in solar activity. This has implications for interpreting the relative contribution of climate drivers of recent ‘global warming’.
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| 5. |
- Chambers, Frank M., et al.
(författare)
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Development and refinement of proxy-climate indicators from peats
- 2012
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Ingår i: Quaternary International. - Oxford : Pergamon Press. - 1040-6182 .- 1873-4553. ; 268, s. 21-33
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Tidskriftsartikel (refereegranskat)abstract
- Peat, especially from acidic mires (bogs), is a natural archive of past environmental change. Reconstructions of past climate from bogs commenced in the 19th Century through examination of visible peat stratigraphy, and later formed the basis for a postglacial climatic scheme widely used in Northwest Europe. Nevertheless, misconceptions as to how bogs grow led to a 50-year lacuna in peat-climate study, before the concept of 'cyclic regeneration' in bogs was refuted. In recent decades, research using proxy-climate indicators from bogs has burgeoned. A range of proxies for past hydrological change has been developed, as well as use of pollen, bog oaks and pines and other data to reconstruct past temperatures. Most of this proxy-climate research has been carried out in Northern Europe, but peat-based research in parts of Asia and North America has increased, particularly during the last decade, while research has also been conducted in Australia, New Zealand and South America. This paper reviews developments in proxy-climate reconstructions from peatlands; chronicles use of a range of palaeo-proxies such as visible peat stratigraphy, plant macrofossils, peat humification, testate amoebae and non-pollen palynomorphs: and explains the use of wiggle-match radiocarbon dating and relationship to climate shifts. It details other techniques being used increasingly, such as biomarkers, stable-isotopes, inorganic geochemistry and estimation of dust flux: and points to new proxies under development. Although explicit protocols have been developed recently for research on ombrotrophic mires, it must be recognised that not all proxies and techniques have universal applicability, owing to differences in species assemblages, mire formation, topographic controls, and geochemical characteristics. (C) 2011 Elsevier Ltd and INQUA. All rights reserved.
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| 6. |
- de Jong, Rixt, et al.
(författare)
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Climate and Peatlands
- 2010
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Ingår i: Changing Climates, Earth Systems and Society. - Dordrecht : Springer Netherlands. - 9789048187157 - 9789048187164 ; , s. 85-121
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Peatlands are an important natural archive for past climatic changes, primarily due to their sensitivity to changes in the water balance and the dating possibilities of peat sediments. In addition, peatlands are an important sink as well as potential source of greenhouse gases. The first part of this chapter discusses a range of well-established and novel proxies studied in peat cores (peat humification, macrofossils, testate amoebae, stomatal records from subfossil leaves, organic biomarkers and stable isotope ratios, aeolian sediment influx and geochemistry) that are used for climatic and environmental reconstructions, as well as recent developments in the dating of these sediments. The second part focuses on the role that peatland ecosystems may play as a source or sink of greenhouse gases. Emphasis is placed on the past and future development of peatlands in the discontinuous permafrost areas of northern Scandinavia, and the role of regenerating mined peatlands in north-western Europe as a carbon sink or source.
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| 7. |
- Gallego-Sala, Angela V., et al.
(författare)
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Latitudinal limits to the predicted increase of the peatland carbon sink with warming
- 2018
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 8:10, s. 907-
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Tidskriftsartikel (refereegranskat)abstract
- The carbon sink potential of peatlands depends on the balance of carbon uptake by plants and microbial decomposition. The rates of both these processes will increase with warming but it remains unclear which will dominate the global peatland response. Here we examine the global relationship between peatland carbon accumulation rates during the last millennium and planetary-scale climate space. A positive relationship is found between carbon accumulation and cumulative photosynthetically active radiation during the growing season for mid- to high-latitude peatlands in both hemispheres. However, this relationship reverses at lower latitudes, suggesting that carbon accumulation is lower under the warmest climate regimes. Projections under Representative Concentration Pathway (RCP)2.6 and RCP8.5 scenarios indicate that the present-day global sink will increase slightly until around AD 2100 but decline thereafter. Peatlands will remain a carbon sink in the future, but their response to warming switches from a negative to a positive climate feedback (decreased carbon sink with warming) at the end of the twenty-first century.
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| 8. |
- Li, Chuxian, et al.
(författare)
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Mercury deposition and redox transformation processes in peatland constrained by mercury stable isotopes
- 2023
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Peatland vegetation takes up mercury (Hg) from the atmosphere, typically contributing to net production and export of neurotoxic methyl-Hg to downstream ecosystems. Chemical reduction processes can slow down methyl-Hg production by releasing Hg from peat back to the atmosphere. The extent of these processes remains, however, unclear. Here we present results from a comprehensive study covering concentrations and isotopic signatures of Hg in an open boreal peatland system to identify post-depositional Hg redox transformation processes. Isotope mass balances suggest photoreduction of HgII is the predominant process by which 30% of annually deposited Hg is emitted back to the atmosphere. Isotopic analyses indicate that above the water table, dark abiotic oxidation decreases peat soil gaseous Hg0 concentrations. Below the water table, supersaturation of gaseous Hg is likely created more by direct photoreduction of rainfall rather than by reduction and release of Hg from the peat soil. Identification and quantification of these light-driven and dark redox processes advance our understanding of the fate of Hg in peatlands, including the potential for mobilization and methylation of HgII.
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| 9. |
- Loisel, Julie, et al.
(författare)
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A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation
- 2014
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 24:9, s. 1028-1042
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Tidskriftsartikel (refereegranskat)abstract
- Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45 degrees N. It encompasses regions within which peat carbon data have only recently become available, such as the West Siberia Lowlands, the Hudson Bay Lowlands, Kamchatka in Far East Russia, and the Tibetan Plateau. For all northern peatlands, carbon content in organic matter was estimated at 42 +/- 3% (standard deviation) for Sphagnum peat, 51 +/- 2% for non-Sphagnum peat, and at 49 +/- 2% overall. Dry bulk density averaged 0.12 +/- 0.07 g/cm(3), organic matter bulk density averaged 0.11 +/- 0.05 g/cm(3), and total carbon content in peat averaged 47 +/- 6%. In general, large differences were found between Sphagnum and non-Sphagnum peat types in terms of peat properties. Time-weighted peat carbon accumulation rates averaged 23 +/- 2 (standard error of mean) g C/m(2)/yr during the Holocene on the basis of 151 peat cores from 127 sites, with the highest rates of carbon accumulation (25-28 g C/m(2)/yr) recorded during the early Holocene when the climate was warmer than the present. Furthermore, we estimate the northern peatland carbon and nitrogen pools at 436 and 10 gigatons, respectively. The database is publicly available at https://peatlands.lehigh.edu.
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| 10. |
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| 11. |
- Mauquoy, Dmitri, et al.
(författare)
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Peatlands in Tierra del Fuego
- 2006
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Ingår i: The biology of peatlands. - : Oxford University Press, Oxford.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 12. |
- Ryberg, Eleonor Eva Stina, 1989-
(författare)
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Holocene species distributions in boreal peatlands : An exploration of factors driving change using Temporal Paleo-Species Distribution Models
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Northern peatlands are terrestrial ecosystems that provide specialized habitats in which biomass production exceeds decomposition, resulting in accumulation of organic matter. Understanding what factors drive species changes in future climate conditions in these systems is of high importance since this has the potential to affect ecosystem functioning and biodiversity, and by extension carbon sequestration. In ecology, a common method for investigating species’ relationships with climate variation, linked with spatial information, is species distribution modelling (SDM). This method typically uses information about current climate conditions tied to locations of species occurrences, forecasting the effects of change on future geographic distributions based on the implicit assumption that temporal variation can be substituted by contemporary spatial variation. This assumption might not be met for several reasons, namely (1) species changes often occur over much longer time-scales than the ones involved in contemporary ecology, and therefore (2) responses to climatic changes are time-lagged. Incorporating paleo-records of actual (past) changes in species distributions and climate conditions therefore provides a much more direct way to model species responses to climate change. In this project, a combination of methods from the fields of paleoecology and ecology were employed to create a novel approach to explore species distribution changes over time in boreal peatlands. This was done by first reconstructing the vegetation of two proximal peatlands (Store Mosse and Dala Mosse bogs; Paper I and III) in south-central Sweden, followed by statistical modeling of the species data and climatic parameters over time (obtained from independent paleoclimate data; Paper II and III), creating Temporal Paleo-Species Distribution Models (Temporal Paleo-SDMs). Paper I identifies factors driving species changes in Store Mosse bog based on internal (successional steps and biotic interactions) and external (climatic) processes. This study tests the assumption that climate has been the main driver of species change by producing a high-resolution postglacial vegetation reconstruction using macrofossil analysis, which is assessed against a set of independent proxy records representing changes in local and regional hydrology, nutrient input, and temperature. Paper II uses the same high-resolution plant macrofossil dataset from Store Mosse and pairs this with independent information about local and regional climate conditions, nutrient input and fire incidence during the same period to create the first Temporal Paleo-SDM and thereby assess the relationships between bog species and climate variability over time (reaching ~10 000 cal yr BP). Paper III tests the repeatability of the Temporal Paleo-SDM method by applying it to a new high-resolution species dataset from Dala Mosse, using the same climate parameters as in Paper II. This thesis bridges across paleoecology and ecology and shows the power of interdisciplinary collaborations and demonstrates the useful contributions they can make in future peatland research.
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| 13. |
- Sillasoo, Ulle, et al.
(författare)
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Peat multi-proxy from Männikjärve bog as indicators of Late Holocene climate changes in Estonia
- 2007
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 36:1, s. 20-37
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Tidskriftsartikel (refereegranskat)abstract
- As part of a wider project on European climate change over the past 4500 years, a 4.5-m peat core was taken from a lawn microform on Männikjärve bog, Estonia. Several methods were used to yield proxy-climate data: (i) a quadrat and leaf-count method for plant macrofossil data, (ii) testate amoebae analysis, and (iii) colorimetric determination of peat humification. These data are provided with an exceptionally high resolution and precise chronology. Changes in bog surface wetness were inferred using Detrended Correspondence Analysis (DCA) and zonation of macrofossil data, particularly concerning the occurrence of Sphagnum balticum, and a transfer function for water-table depth for testate amoebae data. Based on the results, periods of high bog surface wetness appear to have occurred at c. 3100,3010–2990,2300, 1750–1610, 1510, 1410, 1110, 540 and 310 cal. yr BP, during four longer periods between c. 3170 and 2850 cal. yr BP, 2450 and 2000 cal. yr BP, 1770 and 1530 cal. yr BP and in the period from 880 cal. yr BP until the present. In the period between 1770 and 1530 cal. yr BP, the extension or initiation of a hollow microtope occurred, which corresponds with other research results from Mannikjarve bog. This and other changes towards increasing bog surface wetness may be the responses to colder temperatures and the predominance of a more continental climate in the region, which favoured the development of bog micro-depressions and a complex bog microtopography. Located in the border zone of oceanic and continental climatic sectors, in an area almost without land uplift, this study site may provide valuable information about changes in palaeohydrological and palaeoclimatological conditions in the northern parts of the eastern Baltic Sea region.
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| 14. |
- Van der Putten, Nathalie, et al.
(författare)
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Subantarctic peatlands and their potential as palaeoenvironmental and palaeoclimatic archives
- 2012
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Ingår i: Quaternary International. - : Elsevier BV. - 1873-4553 .- 1040-6182. ; 268, s. 65-76
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Tidskriftsartikel (refereegranskat)abstract
- Subantarctic islands are located within the Antarctic Circumpolar Current and the southern westerly wind belt, the latter called Southern Westerlies, making them unique terrestrial archives to investigate past changes in oceanic and atmospheric circulation patterns in the southern mid-latitudes. The islands are characterised by a treeless, phanerogam-poor flora in which bryophytes are of major importance. Several peat-based Holocene palaeoenvironmental and palaeoclimatic studies have recently been published for South Georgia and Ile de la Possession (Iles Crozet). A range of techniques have been used in these studies, mainly plant macrofossil analysis, but also analyses of diatoms, pollen and non-pollen microfossils, geochemical and geomagnetic measurements. The records are chronologically constrained by radiocarbon dating. This paper brings together these data in order to give an overview of the Subantarctic peat-based palaeoclimatic records. A new plant macrofossil record for the island of South Georgia is added. Evidence for millennial scale Holocene climate variability was found for both islands of which the most striking one occurred in the late Holocene. However, within the uncertainty of the age/ depth models, the timing for this climate shift to wetter and/or colder conditions on South Georgia and windier/wetter conditions on Ile de la Possession is different for both islands. Ile de la Possession (Iles Crozet) seems to follow the Northern Hemisphere climate evolution as the event was dated to w2800 cal BP, a well-known climate event present in many peat-based records in north-western Europe. In contrast, the South Georgian late Holocene climate records reveal a shift around w2200e2000 cal BP
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