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  • 2015-2019  (176)
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  • 1
    Online Resource
    Online Resource
    WTZ RUS: CARBOPERM : Kohlenstoff im Permafrost: Bildung, Umwandlung und Freisetzung : (Teilprojekte 1b, 2a, 3b) : Abschlussbericht : Berichtszeitraum: 01.10.2013-30.09.2016 (2017)
    [Potsdam] : Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
    Details Availability
    Keywords: Forschungsbericht ; Kohlenstoffkreislauf ; Dauerfrostboden
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (48 Seiten, 2,7 MB) , Illustrationen, Diagramme
    URL: https://edocs.tib.eu/files/e01fb17/889809887.pdf
    URL: https://doi.org/10.2314/GBV:889809887
    DOI: 10.2314/GBV:889809887
    Language: German
    Note: Förderkennzeichen BMBF 03 G 0836 B. - Verbund-Nummer 01143470 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Mit deutscher Zusammenfassung
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  • 2
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    Impacts of the spatial extent of pollen-climate calibration-set on the absolute values, range and trends of reconstructed Holocene precipitation (2017)
    Elsevier
    In:  Quaternary Science Reviews, 178 . pp. 37-53.
    Details
    Publication Date: 2020-02-06
    Description: 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 (Pann) during the Holocene (since 11.5 cal ka BP) is reconstructed repeatedly for pollen records from Qinghai Lake (36.7°N, 100.5°E; north-east Tibetan Plateau), Gonghai Lake (38.9°N, 112.2°E; north China) and Sihailongwan Lake (42.3°N, 126.6°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.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.quascirev.2017.10.030
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Biome changes and their inferred climatic drivers in northern and eastern continental Asia at selected times since 40 cal ka bp (2018)
    Springer
    In:  Vegetation History and Archaeobotany, 27 (2). pp. 365-379.
    Details
    Publication Date: 2018-12-17
    Description: Recent global warming is pronounced in high-latitude regions (e.g. northern Asia), and will cause the vegetation to change. Future vegetation trends (e.g. the “arctic greening”) will feed back into atmospheric circulation and the global climate system. Understanding the nature and causes of past vegetation changes is important for predicting the composition and distribution of future vegetation communities. Fossil pollen records from 468 sites in northern and eastern Asia were biomised at selected times between 40 cal ka bp and today. Biomes were also simulated using a climate-driven biome model and results from the two approaches compared in order to help understand the mechanisms behind the observed vegetation changes. The consistent biome results inferred by both approaches reveal that long-term and broad-scale vegetation patterns reflect global- to hemispheric-scale climate changes. Forest biomes increase around the beginning of the late deglaciation, become more widespread during the early and middle Holocene, and decrease in the late Holocene in fringe areas of the Asian Summer Monsoon. At the southern and southwestern margins of the taiga, forest increases in the early Holocene and shows notable species succession, which may have been caused by winter warming at ca. 7 cal ka bp. At the northeastern taiga margin (central Yakutia and northeastern Siberia), shrub expansion during the last deglaciation appears to prevent the permafrost from thawing and hinders the northward expansion of evergreen needle-leaved species until ca. 7 cal ka bp. The vegetation-climate disequilibrium during the early Holocene in the taiga-tundra transition zone suggests that projected climate warming will not cause a northward expansion of evergreen needle-leaved species.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00334-017-0653-8
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Biome changes in Asia since the mid-Holocene – an analysis of different transient Earth system model simulations (2017)
    Copernicus Publications (EGU)
    In:  Climate of the Past, 13 (2). pp. 107-134.
    Details
    Publication Date: 2020-02-06
    Description: 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° in the ensemble mean, ranging from 1.5 to 6° 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° (1–9° in the individual simulations). The forest biomes are expanded north-westward by 2°, ranging from 0 to 4° 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.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/cp-13-107-2017
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Pollen-climate relationships in time (9 ka, 6 ka, 0 ka) and space (upland vs. lowland) in eastern continental Asia (2017)
    Elsevier
    In:  Quaternary Science Reviews, 156 . pp. 1-11.
    Details
    Publication Date: 2020-02-06
    Description: 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 (Pann) and mean temperature of the warmest month (Mtwa) 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 Pann compared with Mtwa for taxa distribution is higher today than it was at 6 ka and 9 ka. In particular, the relevance of Pann 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.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.quascirev.2016.11.027
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Position and orientation of the westerly jet determined Holocene rainfall patterns in China (2019)
    Nature Research
    In:  Nature Communications, 10 (1). Art.Nr. 2376.
    Details
    Publication Date: 2022-01-31
    Description: Proxy-based reconstructions and modeling of Holocene spatiotemporal precipitation patterns for China and Mongolia have hitherto yielded contradictory results indicating that the basic mechanisms behind the East Asian Summer Monsoon and its interaction with the westerly jet stream remain poorly understood. We present quantitative reconstructions of Holocene precipitation derived from 101 fossil pollen records and analyse them with the help of a minimal empirical model. We show that the westerly jet-stream axis shifted gradually southward and became less tilted since the middle Holocene. This was tracked by the summer monsoon rain band resulting in an early-Holocene precipitation maximum over most of western China, a mid-Holocene maximum in north-central and northeastern China, and a late-Holocene maximum in southeastern China. Our results suggest that a correct simulation of the orientation and position of the westerly jet stream is crucial to the reliable prediction of precipitation patterns in China and Mongolia.
    Type: Article , PeerReviewed
    Format: text
    Format: archive
    DOI: 10.1038/s41467-019-09866-8
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Northern Hemisphere biome changes (〉30°N) since 40 cal ka BP and their driving factors inferred from model-data comparisons (2019)
    Elsevier
    In:  Quaternary Science Reviews, 220 . pp. 291-309.
    Details
    Publication Date: 2022-01-31
    Description: 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°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.
    Type: Article , PeerReviewed
    DOI: 10.1016/j.quascirev.2019.07.034
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Elemental and isotopic measurements of macrophyte remains and raw sequence data in sediment core KK12-1, Lake Karakul, Pamir Mountains, Tajikistan (2017)
    PANGAEA
    In:  Supplement to: Heinecke, Liv; Epp, Laura Saskia; Reschke, Maria; Stoof-Leichsenring, Kathleen Rosmarie; Mischke, Steffen; Plessen, Birgit; Herzschuh, Ulrike (2017): 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. Journal of Paleolimnology, 58(3), 403-417, https://doi.org/10.1007/s10933-017-9986-7
    Details
    Publication Date: 2023-03-16
    Description: Due to methodological challenges there are only a few studies that focus on macrophyte dynamics in large lakes despite their notable role in a lake's ecosystem functioning. This study investigates composition and productivity changes of the submerged vegetation of Lake Karakul, Pamir Mountains (Tajikistan), using sedimentary ancient DNA metabarcoding and elemental (C/N) and isotopic (d13C, d15N) measurements of Stuckenia cf. pamirica ((Baagøe) Z.Kaplan; Potamogetonaceae) leaf remains. No Stuckenia cf. pamirica leaf remains were found for 28.7 to 26.1 cal ka BP, when both Potamogetonaceae and Chara (L.) DNA sequences were recorded, suggesting sparse submerged vegetation at the coring site. This agrees with the inference of a deep lake reached using geochemical proxies. From 26.1 to 17.5 cal ka BP a few macrophyte remains and high numbers of Potamogetonaceae sequences were recovered: lake level was probably low, as suggested by other studies on the lake. Another phase of increased numbers of Chara sequences and the absence of Stuckenia cf. pamirica leaf remains was found between 17.5 and 12.2 cal ka BP, which coincides with a lake-level transgression at Lake Karakul as indicated by paleo-shoreline investigations. Analyses of macrophyte remains reveal intermediate paleo-productivity from 6.9 cal ka BP and high paleo-productivity from 2.2 cal ka BP onwards. From comparisons with other studies, we suggest that lake-level changes are the main driver for the submerged vegetation composition and productivity at the coring site in Lake Karakul and underline our conclusions by depicting the present-day distribution of Stuckenia cf. pamirica and Chara within the lake.
    Keywords: AWI_Envi; AWI_PerDyn; Permafrost Research (Periglacial Dynamics) @ AWI; Polar Terrestrial Environmental Systems @ AWI
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 9
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    Population genetics analyses of larch tree stands in north-central Siberia (2018)
    PANGAEA
    In:  Supplement to: Kruse, Stefan; Epp, Laura Saskia; Wieczorek, Mareike; Pestryakova, Luidmila A; Stoof-Leichsenring, Kathleen Rosmarie; Herzschuh, Ulrike (2018): High gene flow and complex treeline dynamics of Larix Mill. stands on the Taymyr Peninsula (north-central Siberia) revealed by nuclear microsatellites. Tree Genetics & Genomes, 14(2), https://doi.org/10.1007/s11295-018-1235-3
    Details
    Publication Date: 2023-03-16
    Description: Arctic treelines are facing a strong temperature increase as a result of recent global warming, causing possible changes in forest extent, which will alter vegetation-climate feedbacks. However, the mode and strength of the response is rather unclear, as potential changes are happening in areas that are very remote and difficult to access, and empirical data are still largely lacking. Here, we assessed the current population structure and genetic differentiation of Larix Mill. tree stands within the northernmost latitudinal treeline reaching ~72° N in the southern lowlands of the Taymyr Peninsula (~100° E). We sampled 743 individuals belonging to different height classes (seedlings, saplings, trees) at eleven locations along a gradient from 'single tree' tundra over 'forest line' to 'dense forest' stands and conducted investigations applying eight highly polymorphic nuclear microsatellites. Results suggest a high diversity within subpopulations (HE=0.826-0.893), coupled, however, with heterozygote deficits in all subpopulations, but pronounced in 'forest line' stands. Overall, genetic differentiation of subpopulations is low (FST=0.005), indicating a region-wide high gene flow, although 'forest line' stands harbour few rare and private alleles, likely indicating greater local reproduction. 'Single tree' stands, located beyond the northern forest line, are currently not involved in treeline expansion, but show signs of a long-term refuge, namely asexual reproduction and change of growth-form from erect to creeping growth, possibly having persisted for thousands of years. The lack of differentiation between the subpopulations points to a sufficiently high dispersal potential, and thus a rapid northward migration of the Siberian arctic treeline under recent global warming seems potentially unconstrained, but observations show it to be unexpectedly slow.
    Keywords: AWI_Envi; Polar Terrestrial Environmental Systems @ AWI
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 10
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    Hydrography measured in lakes during the North Yakutia expedition in 2006 (2016)
    PANGAEA
    In:  Alfred Wegener Institute - Research Unit Potsdam
    Details
    Publication Date: 2023-03-14
    Keywords: 06-CYak-01; 06-CYak-02; 06-CYak-03; 06-CYak-04; 06-CYak-05; 06-NYak-01; 06-NYak-02; 06-NYak-03; 06-NYak-04; 06-NYak-05; 06-NYak-06; 06-NYak-07; 06-NYak-08; 06-NYak-09; 06-NYak-10; 06-NYak-11; 06-NYak-12; 06-NYak-13; 06-NYak-14; 06-NYak-15; Alaas; AWI_PerDyn; AWI Arctic Land Expedition; Ayan; Central Yakutia, Russia; Chat; Comment of event; Conductivity; Date/Time of event; Depth of Secchi Disk; Dulla; Etektyak; Event label; Ilimniir; Ivanovka; Kerdugen; Ketitiki; Krestyak; Latitude of event; Longitude of event; MULT; Multiple investigations; Nami-Kuel; North_Yakutia_2006; North Yakutia, Russia; Oibon-Kuel; Oloror; Oppoyao; Optional event label; Otto; Oxygen; Oxygen saturation; Permafrost Research (Periglacial Dynamics) @ AWI; pH; RU-Land_2006_Yakutia; Spasskoe; Suturuoka; Temperature, water; Thee-Bihii; Timpi; Ushepes
    Type: Dataset
    Format: text/tab-separated-values, 120 data points
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    DATA PANGAEA
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