TY - JOUR A1 - Courtin, Jérémy A1 - Andreev, Andrei A1 - Raschke, Elena A1 - Bala, Sarah A1 - Biskaborn, Boris A1 - Liu, Sisi A1 - Zimmermann, Heike A1 - Diekmann, Bernhard A1 - Stoof-Leichsenring, Kathleen R. A1 - Pestryakova, Luidmila Agafyevna A1 - Herzschuh, Ulrike T1 - Vegetation changes in Southeastern Siberia during the late pleistocene and the holocene JF - Frontiers in Ecology and Evolution N2 - Relationships between climate, species composition, and species richness are of particular importance for understanding how boreal ecosystems will respond to ongoing climate change. This study aims to reconstruct changes in terrestrial vegetation composition and taxa richness during the glacial Late Pleistocene and the interglacial Holocene in the sparsely studied southeastern Yakutia (Siberia) by using pollen and sedimentary ancient DNA (sedaDNA) records. Pollen and sedaDNA metabarcoding data using the trnL g and h markers were obtained from a sediment core from Lake Bolshoe Toko. Both proxies were used to reconstruct the vegetation composition, while metabarcoding data were also used to investigate changes in plant taxa richness. The combination of pollen and sedaDNA approaches allows a robust estimation of regional and local past terrestrial vegetation composition around Bolshoe Toko during the last similar to 35,000 years. Both proxies suggest that during the Late Pleistocene, southeastern Siberia was covered by open steppe-tundra dominated by graminoids and forbs with patches of shrubs, confirming that steppe-tundra extended far south in Siberia. Both proxies show disturbance at the transition between the Late Pleistocene and the Holocene suggesting a period with scarce vegetation, changes in the hydrochemical conditions in the lake, and in sedimentation rates. Both proxies document drastic changes in vegetation composition in the early Holocene with an increased number of trees and shrubs and the appearance of new tree taxa in the lake's vicinity. The sedaDNA method suggests that the Late Pleistocene steppe-tundra vegetation supported a higher number of terrestrial plant taxa than the forested Holocene. This could be explained, for example, by the "keystone herbivore" hypothesis, which suggests that Late Pleistocene megaherbivores were able to maintain a high plant diversity. This is discussed in the light of the data with the broadly accepted species-area hypothesis as steppe-tundra covered such an extensive area during the Late Pleistocene. KW - last glacial KW - Holocene KW - Lake Bolshoe Toko KW - paleoenvironments KW - sedimentary ancient DNA KW - metabarcoding KW - trnL KW - pollen Y1 - 2021 U6 - https://doi.org/10.3389/fevo.2021.625096 SN - 2296-701X VL - 9 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Herzschuh, Ulrike T1 - Legacy of the Last Glacial on the present-day distribution of deciduous versus evergreen boreal forests JF - Global ecology and biogeography : a journal of macroecology N2 - Issue Despite their rather similar climatic conditions, eastern Eurasia and northern North America are largely covered by different plant functional types (deciduous or evergreen boreal forest) composed of larch or pine, spruce and fir, respectively. I propose that these deciduous and evergreen boreal forests represent alternative quasi-stable states, triggered by their different northern tree refugia that reflect the different environmental conditions experienced during the Last Glacial. Evidence This view is supported by palaeoecological and environmental evidence. Once established, Asian larch forests are likely to have stabilized through a complex vegetation-fire-permafrost soil-climate feedback system. Conclusion With respect to future forest developments, this implies that Asian larch forests are likely to be governed by long-term trajectories and are therefore largely resistant to natural climate variability on time-scales shorter than millennia. The effects of regional human impact and anthropogenic global warming might, however, cause certain stability thresholds to be crossed, meaning that irreversible transitions occur and resulting in marked consequences for ecosystem services on these human-relevant time-scales. KW - boreal forests KW - Glacial refugia KW - Holocene KW - Larix larch KW - permafrost ecosystems KW - Palaeoecology KW - Siberia KW - vegetation-climate-fire-soil feedbacks KW - vegetation states KW - vegetation trajectories Y1 - 2018 U6 - https://doi.org/10.1111/geb.13018 SN - 1466-822X SN - 1466-8238 VL - 29 IS - 2 SP - 198 EP - 206 PB - John Wiley & Sons, Inc. CY - Hoboken ER - TY - JOUR A1 - Cao, Xianyong A1 - Tian, Fang A1 - Dallmeyer, Anne A1 - Herzschuh, Ulrike T1 - Northern Hemisphere biome changes (> 30 degrees N) since 40 cal ka BP and their driving factors inferred from model-data comparisons JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Ongoing and past biome transitions are generally assigned to climate and atmospheric changes (e.g. temperature, precipitation, CO2), but the major regional factors or factor combinations that drive vegetation change often remain unknown. Modelling studies applying ensemble runs can help to partition the effects of the different drivers. Such studies require careful validation with observational data. In this study, fossil pollen records from 741 sites in Europe, 728 sites in North America, and 418 sites in Asia (extracted from terrestrial archives including lake sediments) are used to reconstruct biomes at selected time slices between 40 cal ka BP (calibrated thousand years before present) and today. These results are used to validate Northern Hemisphere biome distributions (>30 degrees N) simulated by the biome model BIOME4 that has been forced with climate data simulated by a General Circulation model. Quantitative comparisons between pollen- and model-based results show a generally good fit at a broad spatial scale. Mismatches occur in central-arid Asia with a broader extent of grassland throughout the last 40 ka (likely due to the over-representation of Artemisia and Chenopodiaceae pollen) and in Europe with over-estimation of tundra at 0 cal ka BP (likely due to human impacts to some extent). Sensitivity analysis reveals that broad-scale biome changes follow the global signal of major postglacial temperature change, although the climatic variables vary in their regional and temporal importance. Temperature is the dominant variable in Europe and other rather maritime areas for biome changes between 21 and 14 ka, while precipitation is highly important in the arid inland regions of Asia and North America. The ecophysiological effect of changes in the atmospheric CO2-concentration has the highest impact during this transition than in other intervals. With respect to modern vegetation in the course of global warming, our findings imply that vegetation change in the Northern Hemisphere may be strongly limited by effective moisture changes, i.e. the combined effect of temperature and precipitation, particularly in inland areas. (C) 2019 Elsevier Ltd. All rights reserved. KW - Biomisation KW - Climate warming KW - Europe KW - Holocene KW - Model-data comparison KW - Northern Asia KW - North America KW - Pollen KW - Siberia KW - Vegetation driver Y1 - 2019 U6 - https://doi.org/10.1016/j.quascirev.2019.07.034 SN - 0277-3791 VL - 220 SP - 291 EP - 309 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Cao, Xianyong A1 - Tian, Fang A1 - Telford, Richard J. A1 - Ni, Jian A1 - Xu, Qinghai A1 - Chen, Fahu A1 - Liu, Xingqi A1 - Stebich, Martina A1 - Zhao, Yan A1 - Herzschuh, Ulrike T1 - Impacts of the spatial extent of pollen-climate calibration-set on the absolute values, range and trends of reconstructed Holocene precipitation JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - 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. KW - Analogue quality KW - Statistical significance KW - Cross-validation KW - Holocene KW - Climate reconstruction KW - WA-PLS KW - MAT Y1 - 2017 U6 - https://doi.org/10.1016/j.quascirev.2017.10.030 SN - 0277-3791 VL - 178 SP - 37 EP - 53 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Syrykh, Lydmila S. A1 - Nazarova, Larisa B. A1 - Herzschuh, Ulrike A1 - Subetto, D. A. A1 - Grekov, I. M. T1 - Reconstruction of palaeoecological and palaeoclimatic conditions of the Holocene in the south of the Taimyr according to an analysis of lake sediments JF - Contemporary Problems of Ecology N2 - 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. KW - Chironomidae KW - paleolimnology KW - Holocene KW - climate reconstructions KW - Russian Arctic region KW - Khatanga Y1 - 2017 U6 - https://doi.org/10.1134/S1995425517040114 SN - 1995-4255 SN - 1995-4263 VL - 10 SP - 363 EP - 369 PB - Pleiades Publ. CY - New York ER - TY - JOUR A1 - Marquer, Laurent A1 - Gaillard, Marie-Jose A1 - Sugita, Shinya A1 - Poska, Anneli A1 - Trondman, Anna-Kari A1 - Mazier, Florence A1 - Nielsen, Anne Birgitte A1 - Fyfe, Ralph M. A1 - Jonsson, Anna Maria A1 - Smith, Benjamin A1 - Kaplan, Jed O. A1 - Alenius, Teija A1 - Birks, H. John B. A1 - Bjune, Anne E. A1 - Christiansen, Jorg A1 - Dodson, John A1 - Edwards, Kevin J. A1 - Giesecke, Thomas A1 - Herzschuh, Ulrike A1 - Kangur, Mihkel A1 - Koff, Tiiu A1 - Latalowa, Maligorzata A1 - Lechterbeck, Jutta A1 - Olofsson, Jorgen A1 - Seppa, Heikki T1 - Quantifying the effects of land use and climate on Holocene vegetation in Europe JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - 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. KW - Climate KW - Holocene KW - Human impact KW - Land use KW - LPJ-GUESS KW - Europe KW - Pollen KW - REVEALS KW - Vegetation composition Y1 - 2017 U6 - https://doi.org/10.1016/j.quascirev.2017.07.001 SN - 0277-3791 VL - 171 SP - 20 EP - 37 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Wang, Yongbo A1 - Bekeschus, Benjamin A1 - Handorf, Doerthe A1 - Liu, Xingqi A1 - Dallmeyer, Anne A1 - Herzschuh, Ulrike T1 - Coherent tropical-subtropical Holocene see-saw moisture patterns in the Eastern Hemisphere monsoon systems JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - 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. KW - Global monsoon KW - Holocene KW - Eastern hemisphere KW - Moisture evolution Y1 - 2017 U6 - https://doi.org/10.1016/j.quascirev.2017.06.006 SN - 0277-3791 VL - 169 SP - 231 EP - 242 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Mischke, Steffen A1 - Lai, Zhongping A1 - Aichner, Bernhard A1 - Heinecke, Liv A1 - Mahmoudov, Zafar A1 - Kuessner, Marie A1 - Herzschuh, Ulrike T1 - Radiocarbon and optically stimulated luminescence dating of sediments from Lake Karakul, Tajikistan JF - Quaternary geochronology : the international research and review journal on advances in quaternary dating techniques N2 - 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. KW - Radiocarbon and OSL dating KW - Lake sediments KW - Pamir mountains KW - Late pleistocene KW - Holocene Y1 - 2017 U6 - https://doi.org/10.1016/j.quageo.2017.05.008 SN - 1871-1014 SN - 1878-0350 VL - 41 SP - 51 EP - 61 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Tian, Fang A1 - Cao, Xianyong A1 - Dallmeyer, Anne A1 - Zhao, Yan A1 - Ni, Jian A1 - Herzschuh, Ulrike T1 - Pollen-climate relationships in time (9 ka, 6 ka, 0 ka) and space (upland vs. lowland) in eastern continental Asia JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - 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. KW - Boosted regression trees KW - China KW - Holocene KW - Niche stability KW - Pollen-climate relationship KW - Uniformitarianism Y1 - 2016 U6 - https://doi.org/10.1016/j.quascirev.2016.11.027 SN - 0277-3791 VL - 156 SP - 1 EP - 11 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Cao, Xianyong A1 - Herzschuh, Ulrike A1 - Ni, Jian A1 - Zhao, Yan A1 - Böhmer, Thomas T1 - Spatial and temporal distributions of major tree taxa in eastern continental Asia during the last 22,000 years JF - The Holocene : an interdisciplinary journal focusing on recent environmental change N2 - This study investigates the spatial and temporal distributions of 14 key arboreal taxa and their driving forces during the last 22,000 calendar years before ad 1950 (kyr BP) using a taxonomically harmonized and temporally standardized fossil pollen dataset with a 500-year resolution from the eastern part of continental Asia. Logistic regression was used to estimate pollen abundance thresholds for vegetation occurrence (presence or dominance), based on modern pollen data and present ranges of 14 taxa in China. Our investigation reveals marked changes in spatial and temporal distributions of the major arboreal taxa. The thermophilous (Castanea, Castanopsis, Cyclobalanopsis, Fagus, Pterocarya) and eurythermal (Juglans, Quercus, Tilia, Ulmus) broadleaved tree taxa were restricted to the current tropical or subtropical areas of China during the Last Glacial Maximum (LGM) and spread northward since c. 14.5kyr BP. Betula and conifer taxa (Abies, Picea, Pinus), in contrast, retained a wider distribution during the LGM and showed no distinct expansion direction during the Late Glacial. Since the late mid-Holocene, the abundance but not the spatial extent of most trees decreased. The changes in spatial and temporal distributions for the 14 taxa are a reflection of climate changes, in particular monsoonal moisture, and, in the late Holocene, human impact. The post-LGM expansion patterns in eastern continental China seem to be different from those reported for Europe and North America, for example, the westward spread for eurythermal broadleaved taxa. KW - China KW - Holocene KW - Last Glacial Maximum KW - pollen mapping KW - vegetation expansion Y1 - 2015 U6 - https://doi.org/10.1177/0959683614556385 SN - 0959-6836 SN - 1477-0911 VL - 25 IS - 1 SP - 79 EP - 91 PB - Sage Publ. CY - London ER -