@article{GluecklerHerzschuhKruseetal.2021, author = {Gl{\"u}ckler, Ramesh and Herzschuh, Ulrike and Kruse, Stefan and Andreev, Andrei and Vyse, Stuart Andrew and Winkler, Bettina and Biskaborn, Boris and Pestryakova, Luidmila Agafyevna and Dietze, Elisabeth}, title = {Wildfire history of the boreal forest of south-western Yakutia (Siberia) over the last two millennia documented by a lake-sediment charcoal record}, series = {Biogeosciences : BG / European Geosciences Union}, volume = {18}, journal = {Biogeosciences : BG / European Geosciences Union}, number = {13}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1726-4170}, doi = {10.5194/bg-18-4185-2021}, pages = {4185 -- 4209}, year = {2021}, abstract = {Wildfires, as a key disturbance in forest ecosystems, are shaping the world's boreal landscapes. Changes in fire regimes are closely linked to a wide array of environmental factors, such as vegetation composition, climate change, and human activity. Arctic and boreal regions and, in particular, Siberian boreal forests are experiencing rising air and ground temperatures with the subsequent degradation of permafrost soils leading to shifts in tree cover and species composition. Compared to the boreal zones of North America or Europe, little is known about how such environmental changes might influence long-term fire regimes in Russia. The larch-dominated eastern Siberian deciduous boreal forests differ markedly from the composition of other boreal forests, yet data about past fire regimes remain sparse. Here, we present a high-resolution macroscopic charcoal record from lacustrine sediments of Lake Khamra (southwest Yakutia, Siberia) spanning the last ca. 2200 years, including information about charcoal particle sizes and morphotypes. Our results reveal a phase of increased charcoal accumulation between 600 and 900 CE, indicative of relatively high amounts of burnt biomass and high fire frequencies. This is followed by an almost 900-year-long period of low charcoal accumulation without significant peaks likely corresponding to cooler climate conditions. After 1750 CE fire frequencies and the relative amount of biomass burnt start to increase again, coinciding with a warming climate and increased anthropogenic land development after Russian colonization. In the 20th century, total charcoal accumulation decreases again to very low levels despite higher fire frequency, potentially reflecting a change in fire management strategies and/or a shift of the fire regime towards more frequent but smaller fires. A similar pattern for different charcoal morphotypes and comparison to a pollen and non-pollen palynomorph (NPP) record from the same sediment core indicate that broad-scale changes in vegetation composition were probably not a major driver of recorded fire regime changes. Instead, the fire regime of the last two millennia at Lake Khamra seems to be controlled mainly by a combination of short-term climate variability and anthropogenic fire ignition and suppression.}, language = {en} } @article{TianHerzschuhMischkeetal.2014, author = {Tian, Fang and Herzschuh, Ulrike and Mischke, Steffen and Schluetz, Frank}, title = {What drives the recent intensified vegetation degradation in Mongolia - Climate change or human activity?}, series = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, volume = {24}, journal = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, number = {10}, publisher = {Sage Publ.}, address = {London}, issn = {0959-6836}, doi = {10.1177/0959683614540958}, pages = {1206 -- 1215}, year = {2014}, abstract = {This study examines the course and driving forces of recent vegetation change in the Mongolian steppe. A sediment core covering the last 55years from a small closed-basin lake in central Mongolia was analyzed for its multi-proxy record at annual resolution. Pollen analysis shows that highest abundances of planted Poaceae and highest vegetation diversity occurred during 1977-1992, reflecting agricultural development in the lake area. A decrease in diversity and an increase in Artemisia abundance after 1992 indicate enhanced vegetation degradation in recent times, most probably because of overgrazing and farmland abandonment. Human impact is the main factor for the vegetation degradation within the past decades as revealed by a series of redundancy analyses, while climate change and soil erosion play subordinate roles. High Pediastrum (a green algae) influx, high atomic total organic carbon/total nitrogen (TOC/TN) ratios, abundant coarse detrital grains, and the decrease of C-13(org) and N-15 since about 1977 but particularly after 1992 indicate that abundant terrestrial organic matter and nutrients were transported into the lake and caused lake eutrophication, presumably because of intensified land use. Thus, we infer that the transition to a market economy in Mongolia since the early 1990s not only caused dramatic vegetation degradation but also affected the lake ecosystem through anthropogenic changes in the catchment area.}, language = {en} } @misc{TianHerzschuhMischkeetal.2014, author = {Tian, Fang and Herzschuh, Ulrike and Mischke, Steffen and Schl{\"u}tz, Frank}, title = {What drives the recent intensified vegetation degradation in Mongolia}, series = {The Holocene}, journal = {The Holocene}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-404201}, pages = {10}, year = {2014}, abstract = {This study examines the course and driving forces of recent vegetation change in the Mongolian steppe. A sediment core covering the last 55years from a small closed-basin lake in central Mongolia was analyzed for its multi-proxy record at annual resolution. Pollen analysis shows that highest abundances of planted Poaceae and highest vegetation diversity occurred during 1977-1992, reflecting agricultural development in the lake area. A decrease in diversity and an increase in Artemisia abundance after 1992 indicate enhanced vegetation degradation in recent times, most probably because of overgrazing and farmland abandonment. Human impact is the main factor for the vegetation degradation within the past decades as revealed by a series of redundancy analyses, while climate change and soil erosion play subordinate roles. High Pediastrum (a green algae) influx, high atomic total organic carbon/total nitrogen (TOC/TN) ratios, abundant coarse detrital grains, and the decrease of C-13(org) and N-15 since about 1977 but particularly after 1992 indicate that abundant terrestrial organic matter and nutrients were transported into the lake and caused lake eutrophication, presumably because of intensified land use. Thus, we infer that the transition to a market economy in Mongolia since the early 1990s not only caused dramatic vegetation degradation but also affected the lake ecosystem through anthropogenic changes in the catchment area.}, language = {en} } @article{KlemmHerzschuhPestryakova2016, author = {Klemm, Juliane and Herzschuh, Ulrike and Pestryakova, Luidmila Agafyevna}, title = {Vegetation, climate and lake changes over the last 7000 years at the boreal treeline in north-central Siberia}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {147}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2015.08.015}, pages = {422 -- 434}, year = {2016}, language = {en} } @article{TabaresJimenezZimmermannDietzeetal.2019, author = {Tabares Jimenez, Ximena del Carmen and Zimmermann, Heike Hildegard and Dietze, Elisabeth and Ratzmann, Gregor and Belz, Lukas and Vieth-Hillebrand, Andrea and Dupont, Lydie and Wilkes, Heinz and Mapani, Benjamin and Herzschuh, Ulrike}, title = {Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers}, series = {Ecology and evolution}, volume = {10}, journal = {Ecology and evolution}, number = {2}, publisher = {Wiley}, address = {Hoboken}, issn = {2045-7758}, doi = {10.1002/ece3.5955}, pages = {962 -- 979}, year = {2019}, abstract = {Shrub encroachment has far-reaching ecological and economic consequences in many ecosystems worldwide. Yet, compositional changes associated with shrub encroachment are often overlooked despite having important effects on ecosystem functioning. We document the compositional change and potential drivers for a northern Namibian Combretum woodland transitioning into a Terminalia shrubland. We use a multiproxy record (pollen, sedimentary ancient DNA, biomarkers, compound-specific carbon (delta C-13) and deuterium (delta D) isotopes, bulk carbon isotopes (delta(13)Corg), grain size, geochemical properties) from Lake Otjikoto at high taxonomical and temporal resolution. We provide evidence that state changes in semiarid environments may occur on a scale of one century and that transitions between stable states can span around 80 years and are characterized by a unique vegetation composition. We demonstrate that the current grass/woody ratio is exceptional for the last 170 years, as supported by n-alkane distributions and the delta C-13 and delta(13)Corg records. Comparing vegetation records to environmental proxy data and census data, we infer a complex network of global and local drivers of vegetation change. While our delta D record suggests physiological adaptations of woody species to higher atmospheric pCO(2) concentration and drought, our vegetation records reflect the impact of broad-scale logging for the mining industry, and the macrocharcoal record suggests a decrease in fire activity associated with the intensification of farming. Impact of selective grazing is reflected by changes in abundance and taxonomical composition of grasses and by an increase of nonpalatable and trampling-resistant taxa. In addition, grain-size and spore records suggest changes in the erodibility of soils because of reduced grass cover. Synthesis. We conclude that transitions to an encroached savanna state are supported by gradual environmental changes induced by management strategies, which affected the resilience of savanna ecosystems. In addition, feedback mechanisms that reflect the interplay between management legacies and climate change maintain the encroached state.}, language = {en} } @article{ZibulskiHerzschuhPestryakova2016, author = {Zibulski, Romy and Herzschuh, Ulrike and Pestryakova, Luidmila Agafyevna}, title = {Vegetation patterns along micro-relief and vegetation type transects in polygonal landscapes of the Siberian Arctic}, series = {Journal of vegetation science}, volume = {27}, journal = {Journal of vegetation science}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1100-9233}, doi = {10.1111/jvs.12356}, pages = {377 -- 386}, year = {2016}, abstract = {QuestionHow important is the effect of micro-relief and vegetation type on the characteristics of vascular plants and bryophytes in low-centred polygons? LocationSiberian Arctic, Russia. MethodsEight low-centred polygons in northern Siberia were surveyed for vegetation along transects running from the rim to the pond via the rim-pond transition of each polygon and across a vegetation type gradient from open forest to tundra. ResultsThe cover of vascular plants and bryophytes displays no significant differences between the rim and rim-pond transition but is significantly lower in the pond section of the polygons. Alpha-diversity of vascular plants decreases strongly from rim to pond, whereas bryophyte diversity in pond plots is significantly distinct from the rim and the rim-pond transition. There is no clear trend in cover for either plant group along the vegetation type transect and only a weak trend in -diversity. However, both gradients are reflected in the compositional turnover. The applied indicator species analysis identified taxa characteristic of certain environmental conditions. Among others, we found vascular plants primarily characteristic of the rim and bryophyte taxa characteristic of each micro-relief level and vegetation type. ConclusionsThe observed gradual pattern in -diversity and composition of polygonal vegetation suggests that micro-relief is the main driver of changes in the vegetation composition, while vegetation type and the related forest cover change are of subordinate importance for polygonal vegetation patterns along the Siberian tree line.}, language = {en} } @article{CourtinAndreevRaschkeetal.2021, author = {Courtin, J{\´e}r{\´e}my and Andreev, Andrei and Raschke, Elena and Bala, Sarah and Biskaborn, Boris and Liu, Sisi and Zimmermann, Heike and Diekmann, Bernhard and Stoof-Leichsenring, Kathleen R. and Pestryakova, Luidmila Agafyevna and Herzschuh, Ulrike}, title = {Vegetation changes in Southeastern Siberia during the late pleistocene and the holocene}, series = {Frontiers in Ecology and Evolution}, volume = {9}, journal = {Frontiers in Ecology and Evolution}, publisher = {Frontiers Media}, address = {Lausanne}, issn = {2296-701X}, doi = {10.3389/fevo.2021.625096}, pages = {18}, year = {2021}, abstract = {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.}, language = {en} } @article{HeineckeFletcherMischkeetal.2018, author = {Heinecke, Liv and Fletcher, W. J. and Mischke, Steffen and Tian, Fang and Herzschuh, Ulrike}, title = {Vegetation change in the eastern Pamir Mountains, Tajikistan, inferred from Lake Karakul pollen spectra of the last 28 kyr}, series = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, volume = {511}, journal = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2018.08.010}, pages = {232 -- 242}, year = {2018}, abstract = {We present a pollen record for last 28 cal kyr BP from the eastern basin of Lake Karakul, the largest lake in Tajikistan, located in the eastern Pamir Mountains at 3915 m asl, a geographically complex region. The pollen record is dominated by Artemisia and Chenopodiaceae, while other taxa, apart from Poaceae, are present in low quantities and rarely exceed 5\% in total. Arboreal pollen occur predominantly from similar to 28 to similar to 13 cal kyr BP, but as likely no trees occurred in the high mountain regions of the eastern Pamir during this time due to the high altitude and cold climate, arboreal taxa are attributed to long distance transport, probably by the Westerlies, the dominant atmospheric circulation. Tree pollen influx decreases strongly after similar to 13 cal kyr BP, allowing the pollen spectra to be interpreted as a regional vegetation signal. We infer that from 27.6 to 19.4 cal kyr BP the eastern Pamir was dominated by dry mountain steppe with low vegetation cover, while from 19.0 to 13.6 cal kyr BP Artemisia values increase and Chenopodiaceae, most herb taxa, and inferred far distant input from arboreal taxa decrease. Between 12.9 and 6.7 cal kyr BP open steppe vegetation dominated with maximum values in Ephedra, and while steppe taxa still dominated the spectra from 5.4 to 1 cal kyr BP, meadow taxa start to increase. During the last millennium, alpine steppe and alpine meadows expanded and a weak human influence can be ascertained from the increase of Asteraceae and the occurrence of Plantago pollen in the spectra.}, language = {en} } @misc{NiemeyerHerzschuhPestryakova2015, author = {Niemeyer, Bastian and Herzschuh, Ulrike and Pestryakova, Luidmila Agafyevna}, title = {Vegetation and lake changes on the southern Taymyr peninsula, northern Siberia, during the last 300 years inferred from pollen and Pediastrum green algae records}, series = {The Holocene}, volume = {25}, journal = {The Holocene}, number = {4}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-404882}, pages = {11}, year = {2015}, abstract = {Siberian arctic vegetation and lake water communities, known for their temperature dependence, are expected to be particularly impacted by recent climate change and high warming rates. However, decadal information on the nature and strength of recent vegetation change and its time lag to climate signals are rare. In this study, we present a Pb-210/Cs-137 dated pollen and Pediastrum species record from a unnamed lake in the south of the Taymyr peninsula covering the period from AD 1706 to 2011. Thirty-nine palynomorphs and 10 morphotypes of Pediastrum species were studied to assess changes in vegetation and lake conditions as probable responses to climate change. We compared the pollen record with Pediastrum species, which we consider to be important proxies of climate changes. Three pollen assemblage zones characterised by Betula nana, Alnus viridis and Larix gmelinii (1706-1808); herbs such as Cyperaceae, Artemisia or Senecio (1808-1879), and higher abundance of Larix pollen (1955-2011) are visible. Also, three Pediastrum assemblage zones show changes of aquatic conditions: higher abundances of Pediastrum boryanum var. brevicorne (1706-1802); medium abundances of P. kawraiskyi and P. integrum (1802-1840 and 1920-1980), indicating cooler conditions while less eutrophic conditions are indicated by P. boryanum, and a mainly balanced composition with only small changes of cold- and warm-adapted Pediastrum species (1965-2011). In general, compositional Pediastrum species turnover is slightly higher than that indicated by pollen data (0.54 vs 0.34 SD), but both are only minor for this treeline location. In conclusion, the relevance of differentiation of Pediastrum species is promising and can give further insights into the relationship between lakes and their surrounding vegetation transferred onto climatic conditions.}, language = {en} } @article{NiemeyerHerzschuhPestryakova2015, author = {Niemeyer, Bastian and Herzschuh, Ulrike and Pestryakova, Luidmila Agafyevna}, title = {Vegetation and lake changes on the southern Taymyr peninsula, northern Siberia, during the last 300 years inferred from pollen and Pediastrum green algae records}, series = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, volume = {25}, journal = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, number = {4}, publisher = {Sage Publ.}, address = {London}, issn = {0959-6836}, doi = {10.1177/0959683614565954}, pages = {596 -- 606}, year = {2015}, abstract = {Siberian arctic vegetation and lake water communities, known for their temperature dependence, are expected to be particularly impacted by recent climate change and high warming rates. However, decadal information on the nature and strength of recent vegetation change and its time lag to climate signals are rare. In this study, we present a Pb-210/Cs-137 dated pollen and Pediastrum species record from a unnamed lake in the south of the Taymyr peninsula covering the period from AD 1706 to 2011. Thirty-nine palynomorphs and 10 morphotypes of Pediastrum species were studied to assess changes in vegetation and lake conditions as probable responses to climate change. We compared the pollen record with Pediastrum species, which we consider to be important proxies of climate changes. Three pollen assemblage zones characterised by Betula nana, Alnus viridis and Larix gmelinii (1706-1808); herbs such as Cyperaceae, Artemisia or Senecio (1808-1879), and higher abundance of Larix pollen (1955-2011) are visible. Also, three Pediastrum assemblage zones show changes of aquatic conditions: higher abundances of Pediastrum boryanum var. brevicorne (1706-1802); medium abundances of P. kawraiskyi and P. integrum (1802-1840 and 1920-1980), indicating cooler conditions while less eutrophic conditions are indicated by P. boryanum, and a mainly balanced composition with only small changes of cold- and warm-adapted Pediastrum species (1965-2011). In general, compositional Pediastrum species turnover is slightly higher than that indicated by pollen data (0.54 vs 0.34 SD), but both are only minor for this treeline location. In conclusion, the relevance of differentiation of Pediastrum species is promising and can give further insights into the relationship between lakes and their surrounding vegetation transferred onto climatic conditions.}, language = {en} }