TY - JOUR A1 - Wieczorek, Mareike A1 - Kruse, Stefan A1 - Epp, Laura Saskia A1 - Kolmogorov, Alexei A1 - Nikolaev, Anatoly N. A1 - Heinrich, Ingo A1 - Jeltsch, Florian A1 - Pestryakova, Luidmila Agafyevna A1 - Zibulski, Romy A1 - Herzschuh, Ulrike T1 - Dissimilar responses of larch stands in northern Siberia to increasing temperatures-a field and simulation based study JF - Ecology : a publication of the Ecological Society of America N2 - 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. KW - climate change KW - closed forest KW - dendroecology KW - forest change KW - latitude KW - recruitment KW - tundra KW - vegetation model Y1 - 2017 U6 - https://doi.org/10.1002/ecy.1887 SN - 0012-9658 SN - 1939-9170 VL - 98 SP - 2343 EP - 2355 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Niemeyer, Bastian A1 - Epp, Laura Saskia A1 - Stoof-Leichsenring, Kathleen Rosemarie A1 - Pestryakova, Luidmila Agafyevna A1 - Herzschuh, Ulrike T1 - A comparison of sedimentary DNA and pollen from lake sediments in recording vegetation composition at the Siberian treeline JF - Molecular ecology resources N2 - 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. KW - environmental DNA KW - metabarcoding KW - pollen KW - Siberia KW - trnL marker KW - vegetation Y1 - 2017 U6 - https://doi.org/10.1111/1755-0998.12689 SN - 1755-098X SN - 1755-0998 VL - 17 SP - e46 EP - e62 PB - Wiley CY - Hoboken 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 - Kruse, Stefan A1 - Wieczorek, Mareike A1 - Jeltsch, Florian A1 - Herzschuh, Ulrike T1 - Treeline dynamics in Siberia under changing climates as inferred from an individual-based model for Larix JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog KW - Forest change KW - IBM KW - ODD model description KW - Larix gmelinii KW - Permafrost ecosystem KW - Time-lag effects Y1 - 2016 U6 - https://doi.org/10.1016/j.ecolmodel.2016.08.003 SN - 0304-3800 SN - 1872-7026 VL - 338 SP - 101 EP - 121 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Stoof-Leichsenring, Kathleen Rosemarie A1 - Herzschuh, Ulrike A1 - Pestryakova, Luidmila Agafyevna A1 - Klemm, Juliane A1 - Epp, Laura Saskia A1 - Tiedemann, Ralph T1 - Genetic data from algae sedimentary DNA reflect the influence of environment over geography JF - Scientific reports N2 - Genetic investigations on eukaryotic plankton confirmed the existence of modern biogeographic patterns, but analyses of palaeoecological data exploring the temporal variability of these patterns have rarely been presented. Ancient sedimentary DNA proved suitable for investigations of past assemblage turnover in the course of environmental change, but genetic relatedness of the identified lineages has not yet been undertaken. Here, we investigate the relatedness of diatom lineages in Siberian lakes along environmental gradients (i.e. across treeline transects), over geographic distance and through time (i.e. the last 7000 years) using modern and ancient sedimentary DNA. Our results indicate that closely-related Staurosira lineages occur in similar environments and less-related lineages in dissimilar environments, in our case different vegetation and co-varying climatic and limnic variables across treeline transects. Thus our study reveals that environmental conditions rather than geographic distance is reflected by diatom-relatedness patterns in space and time. We tentatively speculate that the detected relatedness pattern in Staurosira across the treeline could be a result of adaptation to diverse environmental conditions across the arctic boreal treeline, however, a geographically-driven divergence and subsequent repopulation of ecologically different habitats might also be a potential explanation for the observed pattern. Y1 - 2015 U6 - https://doi.org/10.1038/srep12924 SN - 2045-2322 VL - 5 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Stoof-Leichsenring, Kathleen Rosemarie A1 - Bernhardt, Nadine A1 - Pestryakova, Luidmila Agafyevna A1 - Epp, Laura Saskia A1 - Herzschuh, Ulrike A1 - Tiedemann, Ralph T1 - A combined paleolimnological/genetic analysis of diatoms reveals divergent evolutionary lineages of Staurosira and Staurosirella (Bacillariophyta) in Siberian lake sediments along a latitudinal transect JF - Journal of paleolimnolog N2 - Diatom diversity in lakes of northwest Yakutia (Siberia) was investigated by microscopic and genetic analysis of surface and cored lake sediments, to evaluate the use of sedimentary DNA for paleolimnological diatom studies and to identify obscure genetic diversity that cannot be detected by microscopic methods. Two short (76 and 73 bp) and one longer (577 bp) fragments of the ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcL) gene, encoding the large subunit of the rbcL, were used as genetic markers. Diverse morphological assemblages of diatoms, dominated by small benthic fragilarioid taxa, were retrieved from the sediments of each lake. These minute fragilarioid taxa were examined by scanning electron microscopy, revealing diverse morphotypes in Staurosira and Staurosirella from the different lakes. Genetic analyses indicated a dominance of haplotypes that were assigned to fragilarioid taxa and less genetic diversity in other diatom taxa. The long rbcL_577 amplicon identified considerable diversification among haplotypes clustering within the Staurosira/Staurosirella genera, revealing 19 different haplotypes whose spatial distribution appears to be primarily related to the latitude of the lakes, which corresponds to a vegetation and climate gradient. Our rbcL markers are valuable tools for tracking differences between diatom lineages that are not visible in their morphologies. These markers revealed putatively high genetic diversity within the Staurosira/Staurosirella species complex, at a finer scale than is possible to resolve by microscopic determination. The rbcL markers may provide additional reliable information on the diversity of barely distinguishable minute benthic fragilarioids. Environmental sequencing may thus allow the tracking of spatial and temporal diversification in Siberian lakes, especially in the context of diatom responses to recent environmental changes, which remains a matter of controversy. KW - Arctic lake sediments KW - Diatoms KW - Environmental DNA KW - Intraspecific variation KW - RbcL Y1 - 2014 U6 - https://doi.org/10.1007/s10933-014-9779-1 SN - 0921-2728 SN - 1573-0417 VL - 52 IS - 1-2 SP - 77 EP - 93 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Ni, Jian A1 - Cao, Xianyong A1 - Jeltsch, Florian A1 - Herzschuh, Ulrike T1 - Biome distribution over the last 22,000 yr in China JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Patterns of past vegetation changes over time and space can help facilitate better understanding of the interactions among climate, ecosystem, and human impact. Biome changes in China over the last 22,000 yr (calibrated radiocarbon date, a BP) were numerically reconstructed by using a standard approach of pollen-plant functional type-biome assignment (biomization). The biomization procedure involves pollen data from 2434 surface sites and 228 fossil sites with a high quality of pollen count and C-14 dating, 51 natural and three anthropogenic plant functional types (PFTs), as well as 19 natural and one anthropogenic biome. Surface pollen-based reconstruction of modern natural biome patterns is in good agreement (74.4%) with actual vegetation distribution in China. However, modem large-scale anthropogenic biome reconstruction has not been successful based on the current setup of three anthropogenic PFTs (plantation, secondary, and disturbed PFT) because of the limitation of non-species level pollen identification and the difficulty in the clear assignment of disturbed PFTs. The non-anthropogenic biome distributions of 44 time slices at 500-year intervals show large-scale discrepant and changed vegetation patterns from the last glacial maximum (LGM) to the Holocene throughout China. From 22 ka BP to 19 ka BP, temperate grassland, xerophytic shrubland, and desert dominated northern China, whereas cold or cool forests flourished in central China. Warm-temperate evergreen forests were restricted to far southern China, and tropical forests were absent During 18.5 ka BP to 12 ka BP, cold, cool, and dry biomes extended to some parts of northern, westem, and eastern China. Warm-temperate evergreen and mixed forests gradually expanded to occupy the whole of southern China. A slight northward shift of forest biomes occurred from 15 ka BP to 12 lea BP. During 11.5 ka BP to 9 ka BP, temperate grassland and shrubland gradually stretched to northern and western China. Cold and cool forests widely expanded into northern and central China, as well as in the northern margin of South China along with temperate deciduous forest. Since the early mid-Holocene (approximately 8.5 ka BP to 5.5 ka BP), all forest biomes shifted northward at the expense of herbaceous and shrubby biomes. Simultaneously, cold and cool forest biomes occupied the marginal areas of the Tibetan Plateau and the high mountains in western China. During the middle to late Holocene, from 5 ka to the present, temperate grassland and xerophytic shrubland expanded to the south and east, whereas temperate deciduous forests slightly shifted southward. After 3 lea BP, forest biomes were absent in western China and on the Tibetan plateau surface. Dramatic biome shifts from the LGM to the Holocene were observed in the forest-grassland ecotone and transitional zones between temperate and subtropical climates, between subtropical and tropical regions, and in the mountainous margins of the eastern Tibetan Plateau. Evidence showed more human disturbances during the late Holocene. More pollen records and historical documents are therefore further needed to understand fully the human disturbance-induced large-scale forest changes. In addition, more classifications of anthropogenic biome or land cover, more distinct assignment of pollen taxa to anthropogenic PFTs, and more effective numerical and/or mechanistic techniques in building large-scale human disturbances are required. (C) 2014 Elsevier B.V. All rights reserved. KW - Anthropogenic biome KW - Biomization KW - Holocene KW - Last glacial maximum KW - Plant functional types KW - Pollen dataset Y1 - 2014 U6 - https://doi.org/10.1016/j.palaeo.2014.04.023 SN - 0031-0182 SN - 1872-616X VL - 409 SP - 33 EP - 47 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ni, Jian A1 - Herzschuh, Ulrike T1 - Simulating biome distribution on the Tibetan Plateau using a modified global vegetation model JF - Arctic, antarctic, and alpine research : an interdisciplinary journal N2 - We used a regionally modified global vegetation model (BIOME4-Tibet) to simulate biome distribution on the Tibetan Plateau under current climate conditions derived from regional meteorological observations. The bioclimatic limits (mean temperatures of the coldest and warmest months, minimum temperature, growing degree-days on 5 degrees C and 0 degrees C bases) for some key alpine plant functional types (temperate deciduous and conifer trees, boreal deciduous and conifer trees, desert woody plants, tundra shrubs, cold herbaceous plants, and lichens/forbs) were redefined based on regional vegetation-climate relationships. Modern vegetation maps confirmed that the BIOME4-Tibet model does a better job of simulating biome patterns on the plateau (gridcell agreement 52%) than the original BIOME4 model (35%). This improved model enhanced our ability to simulate temperate conifer forest, cool conifer and mixed forest, evergreen taiga, temperate xerophytic shrubland, temperate grassland and desert, and steppe and shrub tundra biomes, but made a negligible or reduced difference to the prediction of temperate deciduous forest, warm-temperate mixed forest, and three tundra biomes (erect dwarf-shrub tundra, prostrate dwarf-shrub tundra, and cushion forb, lichen, and moss tundra). Future modification of the vegetation model, by increasing the number of shrub and herb plant functional types, re-parameterization of more precise bioclimatic constraints, and improved representation of soil, permafrost, and snow processes, will be needed to better characterize the distribution of alpine vegetation on the Tibetan Plateau. Y1 - 2011 U6 - https://doi.org/10.1657/1938-4246-43.3.429 SN - 1523-0430 VL - 43 IS - 3 SP - 429 EP - 441 PB - Institute of Arctic and Alpine Research, University of Colorado CY - Boulder ER - TY - JOUR A1 - Herzschuh, Ulrike T1 - Palaeo-moisture evolution in monsoonal Central Asia during the last 50,000 years N2 - The late-Quaternary climate history of monsoonal Central Asia was inferred from 75 palaeoclimatic records which provide information about moisture conditions in the last 50 ka (or part of this period). Wet conditions occurred during middle and late Marine Isotope Stage 3, while the Last Glacial Maximum (LGM) was characterized by dry climate conditions in the region. A stepwise climate amelioration is suggested by the climate records following the LGM. Several climate signals of this period, which were reported from high-latitude ice core records, are preserved in archives from monsoonal Central Asia as well. During the early Holocene, high effective moisture was inferred from most records from the area dominated by the Indian Monsoon (e.g. the Tibetan Plateau) suggesting that Holocene optimal climate conditions occurred there during this period. In contrast, areas which are dominated by the South-East Asian monsoon (SE Monsoon) and the Westerlies (in north-western and north-central China, Mongolia) do not uniformly show an early Holocene climate optimum. For this area optimal conditions prevailed during the mid-Holocene. These apparent contradictions can possibly be explained by the regional uplift and descent of air masses in the Holocene. During the early Holocene, strengthened insolation possibly caused an enhanced low-level convergence over the Tibetan Plateau which led to the intensification of the summer monsoon. The strong air uplift caused intensified precipitation and air divergence in the upper troposphere over the Tibetan Plateau. The areas adjacent to the north therefore experienced an intensified descent of air masses and consequently increased aridity. The majority of the palaeoclimatic records suggest reduced effective moisture since the late Holocene in the region. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/02773791 U6 - https://doi.org/10.1016/j.quascirev.2005.02.006 SN - 0277-3791 ER - TY - JOUR A1 - Herzschuh, Ulrike A1 - Kürschner, Harald A1 - Mischke, Steffen T1 - Temperature variability and vertical vegetation belt shifts during the last similar to 50,000 yr in the Qilian Mountains (NE margin of the Tibetan Plateau, China) N2 - A 13.94-m-long sediment core, collected from a medium-sized lake in the Qilian Mountains (NE Tibetan Plateau, China), was analysed palynologically at 81 horizons. The interpretation of indicator taxa yielded various vertical shifts of the vegetation belts. These palaeovegetation results have been checked with lake surface pollen spectra from 8 takes representing different altitudinal vegetation belts. Our main findings are the following: A short period of the late Marine Isotope Stage 3 (around similar to 46,000 yr ago) was characterized by interglacial temperature conditions with a tree line above its present-day altitude. During the LGM, the vicinity of the lake was not covered by ice but by sparse alpine vegetation and alpine deserts, indicating that the climate was colder by similar to 4-7 degrees C than today Markedly higher temperatures were inferred from higher arboreal pollen frequencies between similar to 13,000 and similar to 7000 yr ago with a Holocene temperature optimum and a maximal Picea-Betula mixed-forest expansion between similar to 9000 and similar to 7000 yr ago, when temperatures exceeded the present-day conditions by at least 1-2 degrees C. Alpine steppes and meadows and sub-alpine shrub vegetation dominated around the lake since the middle Holocene, suggesting that vegetation and climate conditions were exceptionally stable in comparison to previous periods. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00335894 U6 - https://doi.org/10.1016/j.yqres.2006.03.001 SN - 0033-5894 ER - TY - JOUR A1 - Herzschuh, Ulrike A1 - Kürschner, Harald A1 - Battarbee, Rick A1 - Holmes, Jonathan T1 - Desert plant pollen production and a 160-year record of vegetation and climate change on the Alashan Plateau, NW China N2 - Recent and subfossil pollen spectra from the Alashan Plateau are presented in order to provide information on desert plant representation and on recent changes in vegetation and climate in this remote area in northern China. The desert vegetation composition is faithfully represented by the surface pollen spectra. The comparison of the desert plant species to the related pollen taxa yielded the following sequence from over-representation to under- representation: Chenopodiaceae, Artemisia, Ephedra fragilis-type s.l., Reaumuria, Nitraria and Calligonum. A 72 cm long sediment record from a small hydrologically-closed inter-dune lake (SE Badan Jilin Sand Sea, southern Alashan Plateau) covering the past similar to 160 years (dated by(137)Cs) was analysed palynologically. Intervals of denser Artemisia coverage on the sand dunes around the lake, indicating wetter climate, occurred from the mid-1850s to the mid-1870s, during the first two decades of the 20th century and from the late 1930s to the beginning of the 1960s Y1 - 2006 UR - http://www.springerlink.com/content/107470 U6 - https://doi.org/10.1007/s00334-005-0031-9 SN - 0939-6314 ER -