@article{HeineckeEppReschkeetal.2017, author = {Heinecke, Liv and Epp, Laura Saskia and Reschke, Maria and Stoof-Leichsenring, Kathleen Rosemarie and Mischke, Steffen and Plessen, Birgit and Herzschuh, Ulrike}, title = {Aquatic macrophyte dynamics in Lake Karakul (Eastern Pamir) over the last 29 cal ka revealed by sedimentary ancient DNA and geochemical analyses of macrofossil remains}, series = {Journal of paleolimnolog}, volume = {58}, journal = {Journal of paleolimnolog}, publisher = {Springer}, address = {Dordrecht}, issn = {0921-2728}, doi = {10.1007/s10933-017-9986-7}, pages = {403 -- 417}, year = {2017}, language = {en} } @article{MarquerGaillardSugitaetal.2017, author = {Marquer, Laurent and Gaillard, Marie-Jose and Sugita, Shinya and Poska, Anneli and Trondman, Anna-Kari and Mazier, Florence and Nielsen, Anne Birgitte and Fyfe, Ralph M. and Jonsson, Anna Maria and Smith, Benjamin and Kaplan, Jed O. and Alenius, Teija and Birks, H. John B. and Bjune, Anne E. and Christiansen, Jorg and Dodson, John and Edwards, Kevin J. and Giesecke, Thomas and Herzschuh, Ulrike and Kangur, Mihkel and Koff, Tiiu and Latalowa, Maligorzata and Lechterbeck, Jutta and Olofsson, Jorgen and Seppa, Heikki}, title = {Quantifying the effects of land use and climate on Holocene vegetation in Europe}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {171}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2017.07.001}, pages = {20 -- 37}, year = {2017}, abstract = {Early agriculture can be detected in palaeovegetation records, but quantification of the relative importance of climate and land use in influencing regional vegetation composition since the onset of agriculture is a topic that is rarely addressed. We present a novel approach that combines pollen-based REVEALS estimates of plant cover with climate, anthropogenic land-cover and dynamic vegetation modelling results. This is used to quantify the relative impacts of land use and climate on Holocene vegetation at a sub-continental scale, i.e. northern and western Europe north of the Alps. We use redundancy analysis and variation partitioning to quantify the percentage of variation in vegetation composition explained by the climate and land-use variables, and Monte Carlo permutation tests to assess the statistical significance of each variable. We further use a similarity index to combine pollen based REVEALS estimates with climate-driven dynamic vegetation modelling results. The overall results indicate that climate is the major driver of vegetation when the Holocene is considered as a whole and at the sub-continental scale, although land use is important regionally. Four critical phases of land-use effects on vegetation are identified. The first phase (from 7000 to 6500 BP) corresponds to the early impacts on vegetation of farming and Neolithic forest clearance and to the dominance of climate as a driver of vegetation change. During the second phase (from 4500 to 4000 BP), land use becomes a major control of vegetation. Climate is still the principal driver, although its influence decreases gradually. The third phase (from 2000 to 1500 BP) is characterised by the continued role of climate on vegetation as a consequence of late-Holocene climate shifts and specific climate events that influence vegetation as well as land use. The last phase (from 500 to 350 BP) shows an acceleration of vegetation changes, in particular during the last century, caused by new farming practices and forestry in response to population growth and industrialization. This is a unique signature of anthropogenic impact within the Holocene but European vegetation remains climatically sensitive and thus may continue to respond to ongoing climate change. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{MischkeLaiAichneretal.2017, author = {Mischke, Steffen and Lai, Zhongping and Aichner, Bernhard and Heinecke, Liv and Mahmoudov, Zafar and Kuessner, Marie and Herzschuh, Ulrike}, title = {Radiocarbon and optically stimulated luminescence dating of sediments from Lake Karakul, Tajikistan}, series = {Quaternary geochronology : the international research and review journal on advances in quaternary dating techniques}, volume = {41}, journal = {Quaternary geochronology : the international research and review journal on advances in quaternary dating techniques}, publisher = {Elsevier}, address = {Oxford}, issn = {1871-1014}, doi = {10.1016/j.quageo.2017.05.008}, pages = {51 -- 61}, year = {2017}, abstract = {Lake Karakul in the eastern Pamirs is a large and closed-basin lake in a partly glaciated catchment. Two parallel sediment cores were collected from 12 m water depth. The cores were correlated using XRF analysis and dated using radiocarbon and OSL techniques. The age results of the two dating methods are generally in agreement. The correlated composite core of 12.26 m length represents continuous accumulation of sediments in the lake basin since 31 ka. The lake reservoir effect (LRE) remained relatively constant over this period. High sediment accumulation rates (SedARs) were recorded before 23 ka and after 6.5 ka. The relatively close position of the coring location near the eastern shore of the lake implies that high SedARs resulted from low lake levels. Thus, high SedARs and lower lake levels before 23 ka probably reflect cold and dry climate conditions that inhibited the arrival of moist air at high elevation in the eastern Pamirs. Low lake levels after 6.5 ka were probably caused by declining temperatures after the warmer early Holocene, which had caused a reduction in water resources stored as snow, ice and frozen ground in the catchment. Low SedARs during 23-6.5 ka suggest increased lake levels in Lake Karakul. A short-lived increase of SedARs at 15 ka probably corresponds to the rapid melting of glaciers in the Karakul catchment during the Greenland Interstadial le, shortly after glaciers in the catchment had reached their maximum extents. The sediment cores from Lake Karakul represent an important climate archive with robust chronology for the last glacial interglacial cycle from Central Asia. (C) 2017 Elsevier B.V. All rights reserved.}, language = {en} } @article{WangBekeschusHandorfetal.2017, author = {Wang, Yongbo and Bekeschus, Benjamin and Handorf, Doerthe and Liu, Xingqi and Dallmeyer, Anne and Herzschuh, Ulrike}, title = {Coherent tropical-subtropical Holocene see-saw moisture patterns in the Eastern Hemisphere monsoon systems}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {169}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2017.06.006}, pages = {231 -- 242}, year = {2017}, abstract = {The concept of a Global Monsoon (GM) has been proposed based on modern precipitation observations, but its application over a wide range of temporal scales is still under debate. Here, we present a synthesis of 268 continental paleo-moisture records collected from monsoonal systems in the Eastern Hemisphere, including the East Asian Monsoon (EAsM), the Indian Monsoon (IM), the East African Monsoon (EAfM), and the Australian Monsoon (AuM) covering the last 18,000 years. The overall pattern of late Glacial to Holocene moisture change is consistent with those inferred from ice cores and marine records. With respect to the last 10,000 years (10 ka), i.e. a period that has high spatial coverage, a Fuzzy c-Means clustering analysis of the moisture index records together with "Xie-Beni" index reveals four clusters of our data set. The paleoclimatic meaning of each cluster is interpreted considering the temporal evolution and spatial distribution patterns. The major trend in the tropical AuM, EAfM, and IM regions is a gradual decrease in moisture conditions since the early Holocene. Moisture changes in the EAsM regions show maximum index values between 8 and 6 ka. However, records located in nearby subtropical areas, i.e. in regions not influenced by the intertropical convergence zone, show an opposite trend compared to the tropical monsoon regions (AuM, EAfM and IM), i.e. a gradual increase. Analyses of modern meteorological data reveal the same spatial patterns as in the paleoclimate records such that, in times of overall monsoon strengthening, lower precipitation rates are observed in the nearby subtropical areas. We explain this pattern as the effect of a strong monsoon circulation suppressing air uplift in nearby subtropical areas, and hence hindering precipitation. By analogy to the modern system, this would mean that during the early Holocene strong monsoon period, the intensified ascending airflows within the monsoon domains led to relatively weaker ascending or even descending airflows in the adjacent subtropical regions, resulting in a precipitation deficit compared to the late Holocene. Our conceptual model therefore integrates regionally contrasting moisture changes into the Global Monsoon hypothesis. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{SyrykhNazarovaHerzschuhetal.2017, author = {Syrykh, Lydmila S. and Nazarova, Larisa B. and Herzschuh, Ulrike and Subetto, D. A. and Grekov, I. M.}, title = {Reconstruction of palaeoecological and palaeoclimatic conditions of the Holocene in the south of the Taimyr according to an analysis of lake sediments}, series = {Contemporary Problems of Ecology}, volume = {10}, journal = {Contemporary Problems of Ecology}, publisher = {Pleiades Publ.}, address = {New York}, issn = {1995-4255}, doi = {10.1134/S1995425517040114}, pages = {363 -- 369}, year = {2017}, abstract = {A sediment core from Khatanga-12 Lake (Taimyr Peninsula, Krasnoyarsk krai) has been studied. The 131.5-cm-long core covers ca. 7100 years of sedimentation. Chironomid analysis, a qualitative reconstruction of the paleoenvironment in the region, and a quantitative reconstruction of variations of the mean July air temperature and in the water depth of the lake have been performed using Northern Russia chironomid-inferred mean July temperature models (Nazarova et al., 2008, 2011, 2015). Khatanga-12 Lake was formed during the Middle Holocene warming as a result of thermokarst processes. The development of the lake ecosystem at different stages of its development was influenced by climatic and cryolithogenic factors. The Middle Holocene warming, which occurred around 7100-6250 cal. years BP, activated thermokarst processes and resulted in the formation of the lake basin. Later, between 6250 and 4500 cal. years BP, a period of cooling took place, as is proved by chironomid analysis. The bottom sediments of the lake during this period were formed by erosion processes on the lake shores. The reconstructed conditions were close to the modern after 2500 cal. years BP.}, language = {en} } @article{DallmeyerClaussenNietal.2017, author = {Dallmeyer, Anne and Claussen, Martin and Ni, Jian and Cao, Xianyong and Wang, Yongbo and Fischer, Nils and Pfeiffer, Madlene and Jin, Liya and Khon, Vyacheslav and Wagner, Sebastian and Haberkorn, Kerstin and Herzschuh, Ulrike}, title = {Biome changes in Asia since the mid-Holocene}, series = {Climate of the past : an interactive open access journal of the European Geosciences Union}, volume = {13}, journal = {Climate of the past : an interactive open access journal of the European Geosciences Union}, number = {2}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1814-9324}, doi = {10.5194/cp-13-107-2017}, pages = {107 -- 134}, year = {2017}, abstract = {The large variety of atmospheric circulation systems affecting the eastern Asian climate is reflected by the complex Asian vegetation distribution. Particularly in the transition zones of these circulation systems, vegetation is supposed to be very sensitive to climate change. Since proxy records are scarce, hitherto a mechanistic understanding of the past spatio-temporal climate-vegetation relationship is lacking. To assess the Holocene vegetation change and to obtain an ensemble of potential mid-Holocene biome distributions for eastern Asia, we forced the diagnostic biome model BIOME4 with climate anomalies of different transient Holocene climate simulations performed in coupled atmosphere-ocean(-vegetation) models. The simulated biome changes are compared with pollen-based biome records for different key regions. In all simulations, substantial biome shifts during the last 6000 years are confined to the high northern latitudes and the monsoon-westerly wind transition zone, but the temporal evolution and amplitude of change strongly depend on the climate forcing. Large parts of the southern tundra are replaced by taiga during the mid-Holocene due to a warmer growing season and the boreal treeline in northern Asia is shifted northward by approx. 4 degrees in the ensemble mean, ranging from 1.5 to 6 degrees in the individual simulations, respectively. This simulated treeline shift is in agreement with pollen-based reconstructions from northern Siberia. The desert fraction in the transition zone is reduced by 21\% during the mid-Holocene compared to pre-industrial due to enhanced precipitation. The desert-steppe margin is shifted westward by 5 degrees (1-9 degrees in the individual simulations). The forest biomes are expanded north-westward by 2 degrees, ranging from 0 to 4 degrees in the single simulations. These results corroborate pollen-based reconstructions indicating an extended forest area in north-central China during the mid-Holocene. According to the model, the forest-to-non-forest and steppe-to-desert changes in the climate transition zones are spatially not uniform and not linear since the mid-Holocene.}, language = {en} } @article{TianCaoDallmeyeretal.2017, author = {Tian, Fang and Cao, Xianyong and Dallmeyer, Anne and Zhao, Yan and Ni, Jian and Herzschuh, Ulrike}, title = {Pollen-climate relationships in time (9 ka, 6 ka, 0 ka) and space (upland vs. lowland) in eastern continental Asia}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {156}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2016.11.027}, pages = {1 -- 11}, year = {2017}, abstract = {Temporal and spatial stability of the vegetation climate relationship is a basic ecological assumption for pollen-based quantitative inferences of past climate change and for predicting future vegetation. We explore this assumption for the Holocene in eastern continental Asia (China, Mongolia). Boosted regression trees (BRT) between fossil pollen taxa percentages (Abies, Artemisia, Betula, Chenopodiaceae, Cyperaceae, Ephedra, Picea, Pinus, Poaceae and Quercus) and climate model outputs of mean annual precipitation (P-ann) and mean temperature of the warmest month (Mt(wa)) for 9 and 6 ka (ka = thousand years before present) were set up and results compared to those obtained from relating modern pollen to modern climate. Overall, our results reveal only slight temporal differences in the pollen climate relationships. Our analyses suggest that the importance of P-ann compared with Mt(wa) for taxa distribution is higher today than it was at 6 ka and 9 ka. In particular, the relevance of P-ann for Picea and Pinus increases and has become the main determinant. This change in the climate tree pollen relationship parallels a widespread tree pollen decrease in north-central China and the eastern Tibetan Plateau. We assume that this is at least partly related to vegetation climate disequilibrium originating from human impact. Increased atmospheric CO2 concentration may have permitted the expansion of moisture-loving herb taxa (Cyperaceae and Poaceae) during the late Holocene into arid/semi-arid areas. We furthermore find that the pollen climate relationship between north-central China and the eastern Tibetan Plateau is generally similar, but that regional differences are larger than temporal differences. In summary, vegetation climate relationships in China are generally stable in space and time, and pollen-based climate reconstructions can be applied to the Holocene. Regional differences imply the calibration-set should be restricted spatially.}, language = {en} } @article{SainiGuentherAichneretal.2017, author = {Saini, Jeetendra and Guenther, Franziska and Aichner, Bernhard and Mischke, Steffen and Herzschuh, Ulrike and Zhang, Chengjun and Maeusbacher, Roland and Gleixner, Gerd}, title = {Climate variability in the past similar to 19,000 yr in NE Tibetan Plateau inferred from biomarker and stable isotope records of Lake Donggi Cona}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {157}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2016.12.023}, pages = {129 -- 140}, year = {2017}, abstract = {We investigated 4.84-m-long sediment record spanning over the Late Glacial and Holocene from Lake Donggi Cona to be able to reconstruct circulation pattern on the Tibetan Plateau (TP). Presently, Lake Donggi Cona is located at the boundaries of Westerlies and Asian monsoon circulations in the northeastern TP. However, the exact timing and stimulating mechanisms for climatic changes and monsoon shifts in this region are still debated. We used a 19-ka-long stable isotope record of sedimentary n-alkanes to address this discrepancy by providing insights into paleohydrological conditions. The SD of nC(23) is influenced by lake water evaporation; the BD. values of sedimentary nC(29) are mainly controlled by moisture source and temperature changes. Long-chain n-alkanes dominate over the core whereas three mean clusters (i.e. microbial, aquatic and terrestrial) can be inferred. Multi-proxies suggest five major episodes in the history of Lake Donggi Cona. The Lake Donggi Cona record indicates that the Late Glacial(18.4-14.8 cal ka BP) was dominated by low productivity of mainly microbial and aquatic organisms. Relatively low delta D values suggest low temperatures and moist conditions eventually caused by stronger Westerlies, winter monsoon and melt-water influence. Likely, the shift (similar to 17.9 cal ka BP) from microbial to enhanced aquatic input suggests either a change from deep to shallow water lake or a break in local stratification. Between 14.8 and 13.0 cal ka BP, variable climatic conditions prevailed. Although the Westerlies weekend, the increase in temperature enhanced the permafrost and snow melting (displayed by a high sedimentary accumulation rate). Higher delta D values indicate increasingly arid conditions with higher temperatures which eventually lead to high evaporative conditions and lowest lake levels. Low vegetation cover and high erosion rates led to high sediment accumulation resulting in stratification followed by anoxia in the terminal lake. From 13.0 to 9.2 cal ka BP, lowered values of 813 along with high contents of terrestrial organic matter marked the early-Holocene warming indicating a further strengthening of summer precipitation and higher lake levels. A cooling trend was observed in the mid-Holocene between 9.2 and 3.0 cal ka BP accompanied by higher moisture availability (displayed by lowered SD values) caused by reduced evaporative conditions due to a drop in temperature and recovering Westerlies. After 3.0 cal ka BP, a decrease in lake productivity and cold and semi-arid conditions prevailed suggesting lower lake levels and reduced moisture from recycled air masses and Westerlies. We propose that the summer monsoon was the predominant moisture source during the Belling-Allered warm complex and early -Holocene followed by Westerlies in mid-to-late Holocene period. Stable carbon isotope values-32\%o indicate the absence of C-4 -type vegetation in the region contradicting with their presence in the Lake Qinghai record. The 81) record from lake Donggi Cona highlights the importance of the interplay between Westerlies and summer monsoon circulation at this location, which is highly dynamic in northeastern plateau compared to the North Atlantic circulation and insolation changes. Consequently lake Donggi Cona might be an important anchor point for environmental reconstructions on the Tibetan Plateau. (C) 2017 The Authors. Published by Elsevier Ltd.}, language = {en} } @article{CaoTianTelfordetal.2017, author = {Cao, Xianyong and Tian, Fang and Telford, Richard J. and Ni, Jian and Xu, Qinghai and Chen, Fahu and Liu, Xingqi and Stebich, Martina and Zhao, Yan and Herzschuh, Ulrike}, title = {Impacts of the spatial extent of pollen-climate calibration-set on the absolute values, range and trends of reconstructed Holocene precipitation}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {178}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2017.10.030}, pages = {37 -- 53}, year = {2017}, abstract = {Pollen-based quantitative reconstructions of past climate variables is a standard palaeoclimatic approach. Despite knowing that the spatial extent of the calibration-set affects the reconstruction result, guidance is lacking as to how to determine a suitable spatial extent of the pollen-climate calibration-set. In this study, past mean annual precipitation (P-ann) during the Holocene (since 11.5 cal ka BP) is reconstructed repeatedly for pollen records from Qinghai Lake (36.7 degrees N, 100.5 degrees E; north-east Tibetan Plateau), Gonghai Lake (38.9 degrees N, 112.2 degrees E; north China) and Sihailongwan Lake (42.3 degrees N, 126.6 degrees E; north-east China) using calibration-sets of varying spatial extents extracted from the modern pollen dataset of China and Mongolia (2559 sampling sites and 168 pollen taxa in total). Results indicate that the spatial extent of the calibration-set has a strong impact on model performance, analogue quality and reconstruction diagnostics (absolute value, range, trend, optimum). Generally, these effects are stronger with the modern analogue technique (MAT) than with weighted averaging partial least squares (WA-PLS). With respect to fossil spectra from northern China, the spatial extent of calibration-sets should be restricted to radii between ca. 1000 and 1500 km because small-scale calibration-sets (<800 km radius) will likely fail to include enough spatial variation in the modern pollen assemblages to reflect the temporal range shifts during the Holocene, while too broad a scale calibration-set (>1500 km radius) will include taxa with very different pollen-climate relationships. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{LiLiuWangetal.2017, author = {Li, Kai and Liu, Xingqi and Wang, Yongbo and Herzschuh, Ulrike and Ni, Jian and Liao, Mengna and Xiao, Xiayun}, title = {Late Holocene vegetation and climate change on the southeastern Tibetan Plateau: Implications for the Indian Summer Monsoon and links to the Indian Ocean Dipole}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {177}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2017.10.020}, pages = {235 -- 245}, year = {2017}, abstract = {The Indian Summer Monsoon (ISM) is one of the most important climate systems, whose variability and driving mechanisms are of broad interest for academic and societal communities. Here, we present a well-dated high-resolution pollen analysis from a 4.82-m long sediment core taken from Basomtso, in the southeastern Tibetan Plateau (TP), which depicts the regional climate changes of the past millennium. Our results show that subalpine coniferous forest was dominant around Basomtso from ca. 867 to ca. 750 cal. yr BP, indicating a warm and semi-humid climate. The timberline in the study area significantly decreased from ca. 750 to ca.100 cal. yr BP, and a cold climate, corresponding to the Little Ice Age (LIA) prevailed. Since ca. 100 cal. yr BP, the vegetation type changed to forest-meadow with rising temperatures and moisture. Ordination analysis reveals that the migration of vegetation was dominated by regional temperatures and then by moisture. Further comparisons between the Basomtso pollen record and the regional temperature reconstructions underscore the relevance of the Basomtso record from the southeastern TP for regional and global climatologies. Our pollen based moisture reconstruction demonstrates the strong multicentennial-scale link to ISM variability, providing solid evidence for the increase of monsoonal strengths over the past four centuries. Spectral analysis indicates the potential influence of solar forcing. However, a closer relationship has been observed between multicentennial ISM variations and Indian Ocean sea surface temperature anomalies (SSTs), suggesting that the variations in monsoonal precipitation over the southeastern TP are probably driven by the Indian Ocean Dipole on the multicentennial scale. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{RamageIrrgangHerzschuhetal.2017, author = {Ramage, Justine Lucille and Irrgang, Anna Maria and Herzschuh, Ulrike and Morgenstern, Anne and Couture, Nicole and Lantuit, Hugues}, title = {Terrain controls on the occurrence of coastal retrogressive thaw slumps along the Yukon Coast, Canada}, series = {Journal of geophysical research : Earth surface}, volume = {122}, journal = {Journal of geophysical research : Earth surface}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9003}, doi = {10.1002/2017JF004231}, pages = {1619 -- 1634}, year = {2017}, abstract = {Retrogressive thaw slumps (RTSs) are among the most active landforms in the Arctic; their number has increased significantly over the past decades. While processes initiating discrete RTSs are well identified, the major terrain controls on the development of coastal RTSs at a regional scale are not yet defined. Our research reveals the main geomorphic factors that determine the development of RTSs along a 238km segment of the Yukon Coast, Canada. We (1) show the current extent of RTSs, (2) ascertain the factors controlling their activity and initiation, and (3) explain the spatial differences in the density and areal coverage of RTSs. We mapped and classified 287 RTSs using high-resolution satellite images acquired in 2011. We highlighted the main terrain controls over their development using univariate regression trees model. Coastal geomorphology influenced both the activity and initiation of RTSs: active RTSs and RTSs initiated after 1972 occurred primarily on terrains with slope angles greater than 3.9 degrees and 5.9 degrees, respectively. The density and areal coverage of RTSs were constrained by the volume and thickness of massive ice bodies. Differences in rates of coastal change along the coast did not affect the model. We infer that rates of coastal change averaged over a 39year period are unable to reflect the complex relationship between RTSs and coastline dynamics. We emphasize the need for large-scale studies of RTSs to evaluate their impact on the ecosystem and to measure their contribution to the global carbon budget. Plain Language Summary Retrogressive thaw slumps, henceforth slumps are a type of landslides that occur when permafrost thaws. Slumps are active landforms: they develop quickly and extend over several hectares. Satellite imagery allows to map such slumps over large areas. Our research shows where slumps develop along a 238 km segment of the Yukon Coast in Canada and explains which environments are most suitable for slump occurrence. We found that active and newly developed slumps were triggered where coastal slopes were greater than 3.9 degrees and 5.9 degrees, respectively. We explain that coastal erosion influences the development of slumps by modifying coastal slopes. We found that the highest density of slumps as well as the largest slumps occurred on terrains with high amounts of ice bodies in the ground. This study provides tools to better identify areas in the Arctic that are prone to slump development.}, language = {en} } @article{WolterLantuitHerzschuhetal.2017, author = {Wolter, Juliane and Lantuit, Hugues and Herzschuh, Ulrike and Stettner, Samuel and Fritz, Michael}, title = {Tundra vegetation stability versus lake-basin variability on the Yukon Coastal Plain (NW Canada) during the past three centuries}, series = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, volume = {27}, journal = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, publisher = {Sage Publ.}, address = {London}, issn = {0959-6836}, doi = {10.1177/0959683617708441}, pages = {1846 -- 1858}, year = {2017}, language = {en} } @article{ZimmermannRaschkeEppetal.2017, author = {Zimmermann, Heike Hildegard and Raschke, Elena and Epp, Laura Saskia and Stoof-Leichsenring, Kathleen Rosemarie and Schirrmeister, Lutz and Schwamborn, Georg and Herzschuh, Ulrike}, title = {The history of tree and shrub taxa on Bol'shoy Lyakhovsky Island (New Siberian Archipelago) since the Last Interglacial Uncovered by Sedimentary Ancient DNA and Pollen Data}, series = {Genes}, volume = {8}, journal = {Genes}, number = {10}, publisher = {MDPI}, address = {Basel}, issn = {2073-4425}, doi = {10.3390/genes8100273}, pages = {273}, year = {2017}, abstract = {Ecosystem boundaries, such as the Arctic-Boreal treeline, are strongly coupled with climate and were spatially highly dynamic during past glacial-interglacial cycles. Only a few studies cover vegetation changes since the last interglacial, as most of the former landscapes are inundated and difficult to access. Using pollen analysis and sedimentary ancient DNA (sedaDNA) metabarcoding, we reveal vegetation changes on Bol'shoy Lyakhovsky Island since the last interglacial from permafrost sediments. Last interglacial samples depict high levels of floral diversity with the presence of trees (Larix, Picea, Populus) and shrubs (Alnus, Betula, Ribes, Cornus, Saliceae) on the currently treeless island. After the Last Glacial Maximum, Larix re-colonised the island but disappeared along with most shrub taxa. This was probably caused by Holocene sea-level rise, which led to increased oceanic conditions on the island. Additionally, we applied two newly developed larch-specific chloroplast markers to evaluate their potential for tracking past population dynamics from environmental samples. The novel markers were successfully re-sequenced and exhibited two variants of each marker in last interglacial samples. SedaDNA can track vegetation changes as well as genetic changes across geographic space through time and can improve our understanding of past processes that shape modern patterns.}, language = {en} } @article{ZimmermannRaschkeEppetal.2017, author = {Zimmermann, Heike Hildegard and Raschke, Elena and Epp, Laura Saskia and Stoof-Leichsenring, Kathleen Rosemarie and Schwamborn, Georg and Schirrmeister, Lutz and Overduin, Pier Paul and Herzschuh, Ulrike}, title = {Sedimentary ancient DNA and pollen reveal the composition of plant organic matter in Late Quaternary permafrost sediments of the Buor Khaya Peninsula (north-eastern Siberia)}, series = {Biogeosciences}, volume = {14}, journal = {Biogeosciences}, number = {3}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1726-4170}, doi = {10.5194/bg-14-575-2017}, pages = {575 -- 596}, year = {2017}, abstract = {Organic matter deposited in ancient, ice-rich permafrost sediments is vulnerable to climate change and may contribute to the future release of greenhouse gases; it is thus important to get a better characterization of the plant organic matter within such sediments. From a Late Quaternary permafrost sediment core from the Buor Khaya Peninsula, we analysed plant-derived sedimentary ancient DNA (sedaDNA) to identify the taxonomic composition of plant organic matter, and undertook palynological analysis to assess the environmental conditions during deposition. Using sedaDNA, we identified 154 taxa and from pollen and non-pollen palynomorphs we identified 83 taxa. In the deposits dated between 54 and 51 kyr BP, sedaDNA records a diverse low-centred polygon plant community including recurring aquatic pond vegetation while from the pollen record we infer terrestrial open-land vegetation with relatively dry environmental conditions at a regional scale. A fluctuating dominance of either terrestrial or swamp and aquatic taxa in both proxies allowed the local hydrological development of the polygon to be traced. In deposits dated between 11.4 and 9.7 kyr BP (13.4-11.1 cal kyr BP), sedaDNA shows a taxonomic turnover to moist shrub tundra and a lower taxonomic richness compared to the older samples. Pollen also records a shrub tundra community, mostly seen as changes in relative proportions of the most dominant taxa, while a decrease in taxonomic richness was less pronounced compared to sedaDNA. Our results show the advantages of using sedaDNA in combination with palynological analyses when macrofossils are rarely preserved. The high resolution of the sedaDNA record provides a detailed picture of the taxonomic composition of plant-derived organic matter throughout the core, and palynological analyses prove valuable by allowing for inferences of regional environmental conditions.}, language = {en} } @article{HeineckeMischkeAdleretal.2017, author = {Heinecke, Liv and Mischke, Steffen and Adler, Karsten and Barth, Anja and Biskaborn, Boris and Plessen, Birgit and Nitze, Ingmar and Kuhn, Gerhard and Rajabov, Ilhomjon and Herzschuh, Ulrike}, title = {Climatic and limnological changes at Lake Karakul (Tajikistan) during the last similar to 29 cal ka}, series = {Journal of paleolimnolog}, volume = {58}, journal = {Journal of paleolimnolog}, publisher = {Springer}, address = {Dordrecht}, issn = {0921-2728}, doi = {10.1007/s10933-017-9980-0}, pages = {317 -- 334}, year = {2017}, abstract = {We present results of analyses on a sediment core from Lake Karakul, located in the eastern Pamir Mountains, Tajikistan. The core spans the last similar to 29 cal ka. We investigated and assessed processes internal and external to the lake to infer changes in past moisture availability. Among the variables used to infer lake-external processes, high values of grain-size end-member (EM) 3 (wide grain-size distribution that reflects fluvial input) and high Sr/Rb and Zr/Rb ratios (coinciding with coarse grain sizes), are indicative of moister conditions. High values in EM1, EM2 (peaks of small grain sizes that reflect long-distance dust transport or fine, glacially derived clastic input) and TiO2 (terrigenous input) are thought to reflect greater influence of dry air masses, most likely of Westerly origin. High input of dust from distant sources, beginning before the Last Glacial Maximum (LGM) and continuing to the late glacial, reflects the influence of dry Westerlies, whereas peaks in fluvial input suggest increased moisture availability. The early to early-middle Holocene is characterised by coarse mean grain sizes, indicating constant, high fluvial input and moister conditions in the region. A steady increase in terrigenous dust and a decrease in fluvial input from 6.6 cal ka BP onwards points to the Westerlies as the predominant atmospheric circulation through to present, and marks a return to drier and even arid conditions in the area. Proxies for productivity (TOC, TOC/TN, TOCBr), redox potential (Fe/Mn) and changes in the endogenic carbonate precipitation (TIC, delta(18) OCarb) indicate changes within the lake. Low productivity characterised the lake from the late Pleistocene until 6.6 cal ka BP, and increased rapidly afterwards. Lake level remained low until the LGM, but water depth increased to a maximum during the late glacial and remained high into the early Holocene. Subsequently, the water level decreased to its present stage. Today the lake system is mainly climatically controlled, but the depositional regime is also driven by internal limnogeological processes.}, language = {en} } @article{WieczorekKruseEppetal.2017, author = {Wieczorek, Mareike and Kruse, Stefan and Epp, Laura Saskia and Kolmogorov, Alexei and Nikolaev, Anatoly N. and Heinrich, Ingo and Jeltsch, Florian and Pestryakova, Luidmila Agafyevna and Zibulski, Romy and Herzschuh, Ulrike}, title = {Dissimilar responses of larch stands in northern Siberia to increasing temperatures-a field and simulation based study}, series = {Ecology : a publication of the Ecological Society of America}, volume = {98}, journal = {Ecology : a publication of the Ecological Society of America}, publisher = {Wiley}, address = {Hoboken}, issn = {0012-9658}, doi = {10.1002/ecy.1887}, pages = {2343 -- 2355}, year = {2017}, abstract = {Arctic and alpine treelines worldwide differ in their reactions to climate change. A northward advance of or densification within the treeline ecotone will likely influence climate-vegetation feedback mechanisms. In our study, which was conducted in the Taimyr Depression in the North Siberian Lowlands, w present a combined field-and model-based approach helping us to better understand the population processes involved in the responses of the whole treeline ecotone, spanning from closed forest to single-tree tundra, to climate warming. Using information on stand structure, tree age, and seed quality and quantity from seven sites, we investigate effects of intra-specific competition and seed availability on the specific impact of recent climate warming on larch stands. Field data show that tree density is highest in the forest-tundra, and average tree size decreases from closed forest to single-tree tundra. Age-structure analyses indicate that the trees in the closed forest and forest-tundra have been present for at least similar to 240 yr. At all sites except the most southerly ones, past establishment is positively correlated with regional temperature increase. In the single-tree tundra, however, a change in growth form from krummholz to erect trees, beginning similar to 130 yr ago, rather than establishment date has been recorded. Seed mass decreases from south to north, while seed quantity increases. Simulations with LAVESI (Larix Vegetation Simulator) further suggest that relative density changes strongly in response to a warming signal in the forest-tundra while intra-specific competition limits densification in the closed forest and seed limitation hinders densification in the single-tree tundra. We find striking differences in strength and timing of responses to recent climate warming. While forest-tundra stands recently densified, recruitment is almost non-existent at the southern and northern end of the ecotone due to autecological processes. Palaeo-treelines may therefore be inappropriate to infer past temperature changes at a fine scale. Moreover, a lagged treeline response to past warming will, via feedback mechanisms, influence climate change in the future.}, language = {en} } @article{NiemeyerEppStoofLeichsenringetal.2017, author = {Niemeyer, Bastian and Epp, Laura Saskia and Stoof-Leichsenring, Kathleen Rosemarie and Pestryakova, Luidmila Agafyevna and Herzschuh, Ulrike}, title = {A comparison of sedimentary DNA and pollen from lake sediments in recording vegetation composition at the Siberian treeline}, series = {Molecular ecology resources}, volume = {17}, journal = {Molecular ecology resources}, publisher = {Wiley}, address = {Hoboken}, issn = {1755-098X}, doi = {10.1111/1755-0998.12689}, pages = {e46 -- e62}, year = {2017}, abstract = {Reliable information on past and present vegetation is important to project future changes, especially for rapidly transitioning areas such as the boreal treeline. To study past vegetation, pollen analysis is common, while current vegetation is usually assessed by field surveys. Application of detailed sedimentary DNA (sedDNA) records has the potential to enhance our understanding of vegetation changes, but studies systematically investigating the power of this proxy are rare to date. This study compares sedDNA metabarcoding and pollen records from surface sediments of 31 lakes along a north-south gradient of increasing forest cover in northern Siberia (Taymyr peninsula) with data from field surveys in the surroundings of the lakes. sedDNA metabarcoding recorded 114 plant taxa, about half of them to species level, while pollen analyses identified 43 taxa, both exceeding the 31 taxa found by vegetation field surveys. Increasing Larix percentages from north to south were consistently recorded by all three methods and principal component analyses based on percentage data of vegetation surveys and DNA sequences separated tundra from forested sites. Comparisons of the ordinations using procrustes and protest analyses show a significant fit among all compared pairs of records. Despite similarities of sedDNA and pollen records, certain idiosyncrasies, such as high percentages of Alnus and Betula in all pollen and high percentages of Salix in all sedDNA spectra, are observable. Our results from the tundra to single-tree tundra transition zone show that sedDNA analyses perform better than pollen in recording site-specific richness (i.e., presence/absence of taxa in the vicinity of the lake) and perform as well as pollen in tracing vegetation composition.}, language = {en} } @article{ZibulskiWesenerWilkesetal.2017, author = {Zibulski, Romy and Wesener, Felix and Wilkes, Heinz and Plessen, Birgit and Pestryakova, Luidmila Agafyevna and Herzschuh, Ulrike}, title = {C / N ratio, stable isotope (delta C-13, delta N-15), and n-alkane patterns of brown mosses along hydrological gradients of low-centred polygons of the Siberian Arctic}, series = {Biogeosciences}, volume = {14}, journal = {Biogeosciences}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1726-4170}, doi = {10.5194/bg-14-1617-2017}, pages = {1617 -- 1630}, year = {2017}, abstract = {Mosses are a major component of the arctic vegetation, particularly in wetlands. We present C / N atomic ratio, delta C-13 and delta N-15 data of 400 brown-moss samples belonging to 10 species that were collected along hydrological gradients within polygonal mires located on the southern Taymyr Peninsula and the Lena River delta in northern Siberia. Additionally, n-alkane patterns of six of these species (16 samples) were investigated. The aim of the study is to see whether the inter-and intraspecific differences in C / N, isotopic compositions and n-alkanes are indicative of habitat, particularly with respect to water level. Overall, we find high variability in all investigated parameters for two different moisture-related groups of moss species. The C / N ratios range between 11 and 53 (median: 32) and show large variations at the intraspecific level. However, species preferring a dry habitat (xero-mesophilic mosses) show higher C / N ratios than those preferring a wet habitat (meso-hygrophilic mosses). The delta C-13 values range between 37.0 and 22.5\% (median D 27.8 \%). The delta N-15 values range between 6.6 and C 1.7\%(median D 2.2 \%). We find differences in delta C-13 and delta N-15 compositions between both habitat types. For some species of the meso-hygrophilic group, we suggest that a relationship between the individ-ual habitat water level and isotopic composition can be inferred as a function of microbial symbiosis. The n-alkane distribution also shows differences primarily between xeromesophilic and meso-hygrophilic mosses, i. e. having a dominance of n-alkanes with long (n-C29, n-C31 /and intermediate (n-C25 /chain lengths, respectively. Overall, our results reveal that C / N ratios, isotopic signals and n-alkanes of studied brown-moss taxa from polygonal wetlands are characteristic of their habitat.}, language = {en} } @article{WieczorekKolmogorovKruseetal.2017, author = {Wieczorek, Mareike and Kolmogorov, Alexei and Kruse, Stefan and Jacobsen, Inga and Nitze, Ingmar and Nikolaev, Anatoly N. and Heinrich, Ingo and Pestryakova, Luidmila Agafyevna and Herzschuh, Ulrike}, title = {Disturbance-effects on treeline larch-stands in the lower Kolyma River area (NE Siberia)}, series = {Silva Fennica : a quarterly journal for forest science}, volume = {51}, journal = {Silva Fennica : a quarterly journal for forest science}, number = {3}, publisher = {The Finnish Society of Forest Science}, address = {Helsinki}, issn = {0037-5330}, doi = {10.14214/sf.1666}, pages = {20}, year = {2017}, abstract = {Tree stands in the boreal treeline ecotone are, in addition to climate change, impacted by disturbances such as fire, water-related disturbances and logging. We aim to understand how these disturbances affect growth, age structure, and spatial patterns of larch stands in the north-eastern Siberian treeline ecotone (lower Kolyma River region), an insufficiently researched region. Stand structure of Larix cajanderi Mayr was studied at seven sites impacted by disturbances. Maximum tree age ranged from 44 to 300 years. Young to medium-aged stands had, independent of disturbance type, the highest stand densities with over 4000 larch trees per ha. These sites also had the highest growth rates for tree height and stem diameter. Overall lowest stand densities were found in a polygonal field at the northern end of the study area, with larches growing in distinct " tree islands". At all sites, saplings are significantly clustered. Differences in fire severity led to contrasting stand structures with respect to tree, recruit, and overall stand densities. While a low severity fire resulted in low-density stands with high proportions of small and young larches, high severity fires resulted in high-density stands with high proportions of big trees. At waterdisturbed sites, stand structure varied between waterlogged and drained sites and latitude. These mixed effects of climate and disturbance make it difficult to predict future stand characteristics and the treeline position.}, language = {en} }