TY - JOUR A1 - Cao, Xianyong A1 - Tian, Fang A1 - Andreev, Andrei A1 - Anderson, Patricia M. A1 - Lozhkin, Anatoly V. A1 - Bezrukova, Elena A1 - Ni, Jian A1 - Rudaya, Natalia A1 - Stobbe, Astrid A1 - Wieczorek, Mareike A1 - Herzschuh, Ulrike T1 - A taxonomically harmonized and temporally standardized fossil pollen dataset from Siberia covering the last 40 kyr JF - Earth System Science Data N2 - Pollen records from Siberia are mostly absent in global or Northern Hemisphere synthesis works. Here we present a taxonomically harmonized and temporally standardized pollen dataset that was synthesized using 173 palynological records from Siberia and adjacent areas (northeastern Asia, 42-75 degrees N, 50-180 degrees E). Pollen data were taxonomically harmonized, i.e. the original 437 taxa were assigned to 106 combined pollen taxa. Age-depth models for all records were revised by applying a constant Bayesian age-depth modelling routine. The pollen dataset is available as count data and percentage data in a table format (taxa vs. samples), with age information for each sample. The dataset has relatively few sites covering the last glacial period between 40 and 11.5 ka (calibrated thousands of years before 1950 CE) particularly from the central and western part of the study area. In the Holocene period, the dataset has many sites from most of the area, with the exception of the central part of Siberia. Of the 173 pollen records, 81 % of pollen counts were downloaded from open databases (GPD, EPD, PANGAEA) and 10 % were contributions by the original data gatherers, while a few were digitized from publications. Most of the pollen records originate from peatlands (48 %) and lake sediments (33 %). Most of the records (83 %) have >= 3 dates, allowing the establishment of reliable chronologies. The dataset can be used for various purposes, including pollen data mapping (example maps for Larix at selected time slices are shown) as well as quantitative climate and vegetation reconstructions. The datasets for pollen counts and pollen percentages are available at https://doi.org/10.1594/PANGAEA.898616 (Cao et al., 2019a), also including the site information, data source, original publication, dating data, and the plant functional type for each pollen taxa. KW - Late Quaternary vegetation KW - Holocene environmental history KW - eastern continental Asia KW - plant macrofossil data KW - late pleistocene KW - paleoenvironmental records KW - Verkhoyansk mountains KW - climate dynamics KW - glacial maximum KW - Northern Asia Y1 - 2020 U6 - https://doi.org/10.5194/essd-12-119-2020 SN - 1866-3508 SN - 1866-3516 VL - 12 IS - 1 SP - 119 EP - 135 PB - Copernics Publications CY - Katlenburg-Lindau ER - TY - JOUR A1 - Dallmeyer, Anne A1 - Kleinen, Thomas A1 - Claussen, Martin A1 - Weitzel, Nils A1 - Cao, Xianyong A1 - Herzschuh, Ulrike T1 - The deglacial forest conundrum JF - Nature Communications N2 - How fast the Northern Hemisphere (NH) forest biome tracks strongly warming climates is largely unknown. Regional studies reveal lags between decades and millennia. Here we report a conundrum: Deglacial forest expansion in the NH extra-tropics occurs approximately 4000 years earlier in a transient MPI-ESM1.2 simulation than shown by pollen-based biome reconstructions. Shortcomings in the model and the reconstructions could both contribute to this mismatch, leaving the underlying causes unresolved. The simulated vegetation responds within decades to simulated climate changes, which agree with pollen-independent reconstructions. Thus, we can exclude climate biases as main driver for differences. Instead, the mismatch points at a multi-millennial disequilibrium of the NH forest biome to the climate signal. Therefore, the evaluation of time-slice simulations in strongly changing climates with pollen records should be critically reassessed. Our results imply that NH forests may be responding much slower to ongoing climate changes than Earth System Models predict.
Deglacial forest expansion in the Northern Hemisphere poses a conundrum: Model results agree with the climate signal but are several millennia ahead of reconstructed forest dynamics. The underlying causes remain unsolved. Y1 - 2022 U6 - https://doi.org/10.1038/s41467-022-33646-6 SN - 2041-1723 VL - 13 IS - 1 PB - Nature Publishing Group UK CY - [London] ER - TY - JOUR A1 - Herzschuh, Ulrike A1 - Böhmer, Thomas A1 - Li, Chenzhi A1 - Cao, Xianyong A1 - Hébert, Raphaël A1 - Dallmeyer, Anne A1 - Telford, Richard J. A1 - Kruse, Stefan T1 - Reversals in temperature-precipitation correlations in the Northern Hemisphere extratropics during the Holocene JF - Geophysical research letters N2 - Future precipitation levels remain uncertain because climate models have struggled to reproduce observed variations in temperature-precipitation correlations. Our analyses of Holocene proxy-based temperature-precipitation correlations and hydrological sensitivities from 2,237 Northern Hemisphere extratropical pollen records reveal a significant latitudinal dependence and temporal variations among the early, middle, and late Holocene. These proxy-based variations are largely consistent with patterns obtained from transient climate simulations (TraCE21k). While high latitudes and subtropical monsoon areas show mainly stable positive correlations throughout the Holocene, the mid-latitude pattern is temporally and spatially more variable. In particular, we identified a reversal from positive to negative temperature-precipitation correlations in the eastern North American and European mid-latitudes from the early to mid-Holocene that mainly related to slowed down westerlies and a switch to moisture-limited convection under a warm climate. Our palaeoevidence of past temperature-precipitation correlation shifts identifies those regions where simulating past and future precipitation levels might be particularly challenging. Y1 - 2022 U6 - https://doi.org/10.1029/2022GL099730 SN - 0094-8276 SN - 1944-8007 VL - 49 IS - 22 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Herzschuh, Ulrike A1 - Cao, Xianyong A1 - Laepple, Thomas A1 - Dallmeyer, Anne A1 - Telford, Richard J. A1 - Ni, Jian A1 - Chen, Fahu A1 - Kong, Zhaochen A1 - Liu, Guangxiu A1 - Liu, Kam-Biu A1 - Liu, Xingqi A1 - Stebich, Martina A1 - Tang, Lingyu A1 - Tian, Fang A1 - Wang, Yongbo A1 - Wischnewski, Juliane A1 - Xu, Qinghai A1 - Yan, Shun A1 - Yang, Zhenjing A1 - Yu, Ge A1 - Zhang, Yun A1 - Zhao, Yan A1 - Zheng, Zhuo T1 - Position and orientation of the westerly jet determined Holocene rainfall patterns in China JF - Nature Communications N2 - 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. Y1 - 2019 U6 - https://doi.org/10.1038/s41467-019-09866-8 SN - 2041-1723 VL - 10 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Jia, Weihan A1 - Anslan, Sten A1 - Chen, Fahu A1 - Cao, Xianyong A1 - Dong, Hailiang A1 - Dulias, Katharina A1 - Gu, Zhengquan A1 - Heinecke, Liv A1 - Jiang, Hongchen A1 - Kruse, Stefan A1 - Kang, Wengang A1 - Li, Kai A1 - Liu, Sisi A1 - Liu, Xingqi A1 - Liu, Ying A1 - Ni, Jian A1 - Schwalb, Antje A1 - Stoof-Leichsenring, Kathleen R. A1 - Shen, Wei A1 - Tian, Fang A1 - Wang, Jing A1 - Wang, Yongbo A1 - Wang, Yucheng A1 - Xu, Hai A1 - Yang, Xiaoyan A1 - Zhang, Dongju A1 - Herzschuh, Ulrike T1 - Sedimentary ancient DNA reveals past ecosystem and biodiversity changes on the Tibetan Plateau: overview and prospects JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Alpine ecosystems on the Tibetan Plateau are being threatened by ongoing climate warming and intensified human activities. Ecological time-series obtained from sedimentary ancient DNA (sedaDNA) are essential for understanding past ecosystem and biodiversity dynamics on the Tibetan Plateau and their responses to climate change at a high taxonomic resolution. Hitherto only few but promising studies have been published on this topic. The potential and limitations of using sedaDNA on the Tibetan Plateau are not fully understood. Here, we (i) provide updated knowledge of and a brief introduction to the suitable archives, region-specific taphonomy, state-of-the-art methodologies, and research questions of sedaDNA on the Tibetan Plateau; (ii) review published and ongoing sedaDNA studies from the Tibetan Plateau; and (iii) give some recommendations for future sedaDNA study designs. Based on the current knowledge of taphonomy, we infer that deep glacial lakes with freshwater and high clay sediment input, such as those from the southern and southeastern Tibetan Plateau, may have a high potential for sedaDNA studies. Metabarcoding (for microorganisms and plants), metagenomics (for ecosystems), and hybridization capture (for prehistoric humans) are three primary sedaDNA approaches which have been successfully applied on the Tibetan Plateau, but their power is still limited by several technical issues, such as PCR bias and incompleteness of taxonomic reference databases. Setting up high-quality and open-access regional taxonomic reference databases for the Tibetan Plateau should be given priority in the future. To conclude, the archival, taphonomic, and methodological conditions of the Tibetan Plateau are favorable for performing sedaDNA studies. More research should be encouraged to address questions about long-term ecological dynamics at ecosystem scale and to bring the paleoecology of the Tibetan Plateau into a new era. KW - Sedimentary ancient DNA (sedaDNA) KW - Tibetan Plateau KW - Environmental DNA KW - Taphonomy KW - Ecosystem KW - Biodiversity KW - Paleoecology KW - Paleogeography Y1 - 2022 U6 - https://doi.org/10.1016/j.quascirev.2022.107703 SN - 0277-3791 SN - 1873-457X VL - 293 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Li, Chenzhi A1 - Postl, Alexander K. A1 - Böhmer, Thomas A1 - Cao, Xianyong A1 - Dolman, Andrew M. A1 - Herzschuh, Ulrike T1 - Harmonized chronologies of a global late Quaternary pollen dataset (LegacyAge 1.0) JF - Earth system science data : ESSD N2 - We present a chronology framework named LegacyAge 1.0 containing harmonized chronologies for 2831 pollen records (downloaded from the Neotoma Paleoecology Database and the supplementary Asian datasets) together with their age control points and metadata in machine-readable data formats. All chronologies use the Bayesian framework implemented in Bacon version 2.5.3. Optimal parameter settings of priors (accumulation.shape, memory.strength, memory.mean, accumulation.rate, and thickness) were identified based on information in the original publication or iteratively after preliminary model inspection. The most common control points for the chronologies are radiocarbon dates (86.1 %), calibrated by the latest calibration curves (IntCal20 and SHCal20 for the terrestrial radiocarbon dates in the Northern Hemisphere and Southern Hemisphere and Marine20 for marine materials). The original publications were consulted when dealing with outliers and inconsistencies. Several major challenges when setting up the chronologies included the waterline issue (18.8% of records), reservoir effect (4.9 %), and sediment deposition discontinuity (4.4 %). Finally, we numerically compare the LegacyAge 1.0 chronologies to those published in the original publications and show that the reliability of the chronologies of 95.4% of records could be improved according to our assessment. Our chronology framework and revised chronologies provide the opportunity to make use of the ages and age uncertainties in synthesis studies of, for example, pollen-based vegetation and climate change. The LegacyAge 1.0 dataset, including metadata, datings, harmonized chronologies, and R code used, is openaccess and available at PANGAEA (https://doi.org/10.1594/PANGAEA.933132; Li et al., 2021) and Zenodo (https://doi.org/10.5281/zenodo.5815192; Li et al., 2022), respectively. Y1 - 2022 U6 - https://doi.org/10.5194/essd-14-1331-2022 SN - 1866-3508 SN - 1866-3516 VL - 14 IS - 3 SP - 1331 EP - 1343 PB - Copernics Publications CY - Katlenburg-Lindau ER - TY - JOUR A1 - Li, Huashu A1 - Liu, Xingqi A1 - Herzschuh, Ulrike A1 - Cao, Xianyong A1 - Yu, Zhitong A1 - Wang, Yong T1 - Vegetation and climate changes since the middle MIS 3 inferred from a Wulagai Lake pollen record, Inner Mongolia, Northeastern China JF - Review of palaeobotany and palynology : an international journal N2 - The climate conditions during Marine Isotope Stage (MIS) 3 were similar to present-day conditions, but whether humidity then exceeded present levels is debated, and the driving mechanisms of palaeoclimate evolution since MIS 3 remain unclear. Here, we use pollen data from Wulagai Lake, Inner Mongolia, to reconstruct vegetation and climate changes since the middle MIS 3. The steppe biome is reconstructed as the first dominant biome and the desert biome as the second, and the results show that the vegetation was steppe over the last 43,800 years. Poaceae, Artemisia, Caryophyllaceae and Humulus were abundant from middle to late MIS 3, indicating humid climate conditions. As drought-tolerant species such as Hippophae, Nitraria and Chenopodiaceae spread during MIS 2, the climate became arid. The Holocene is characterized by the dominance of steppe with mixed coniferous-broadleaved forests in the Greater Hinggan Range, and the desert biome retains high affinity scores, indicating that the climate was semi-arid. The climate from middle to late MIS 3 was wetter than in the Holocene; this shift was related to changes in the Northern Hemisphere's solar insolation and ice volume. The humid conditions during MIS 3 were attributed to strong ice–albedo feedback, which led to evaporation that was less than the precipitation. The enhanced evaporation caused by increased solar insolation and decreased ice volume might have exceeded the precipitation during the Holocene and resulted in low effective humidity in the Wulagai Lake basin. KW - Pollen KW - Biome KW - Ice volume KW - Solar insolation Y1 - 2018 U6 - https://doi.org/10.1016/j.revpalbo.2018.12.006 SN - 0034-6667 SN - 1879-0615 VL - 262 SP - 44 EP - 51 PB - Elsevier CY - Amsterdam ER -