The end of the Pleistocene tundra steppe - interactions between vegetation, climate and large herbivores in Beringia during the late Quaternary (TUNDRA-STEPPE)

本项目拟采用均变说方法，结合古植物学研究成果和对俄罗斯雅库特、前次大陆白令陆桥西部地区现代植物群落的研究，揭示晚第四纪北极地区气候、植被和大型食草动物的生态相互作用。研究结果将有助于了解更新世北极生物地球群落的结构和功能，并有助于了解它们在向全新世过渡过程中的重组和大规模退化。放牧对植被的影响将在现有的更新世公园放牧实验的框架下进行研究，该实验是由东北科学站Cherskii合作在科雷马河下游进行的重建猛犸草原样生态系统的实验。更新世公园实验的结果将一方面与从北方森林到冻土带的主要气候控制梯度沿线未受影响的植被以及雅库特内陆的残余草原植被进行比较，另一方面与同生永久冻土带中记录的重建的晚更新世古植被进行比较。在靠近更新世公园实验的Duvanny Yar永久冻土层中，宏观植物遗迹保存完好，将用于重建东北西伯利亚晚第四纪植被的结构、组成和动态。特别关注晚冰期到全新世的过渡，猛犸象动物群减少，西伯利亚东北部生态系统重构达到高潮。对最后两个间冰期的古植被进行比较也有望有有趣的发现：Eemian （Kazantsevo）时期，植被受到大型食草动物放牧的影响，而全新世时期，放牧被推迟。通过结合这两种方法，我们将确定气候和放牧的相对比例，作为决定西白令陆桥现存和更新世植被特征的潜在主要驱动因素。

The proposed research project intends to reveal the ecological interactions of climate, vegetation and large herbivores in the Arctic during the late Quaternary following an uniformitarianistic approach by combining palaeobotanical results with studies of modern plant communities in Yakutia, Russian Federation, the western part of the former subcontinent Beringia. The results are expected to give insights into structure and functioning of arctic biogeocenoses during the Pleistocene and will contribute to the understanding of their restructuring and massive depauperation in the course of the transition to the Holocene. Grazing effects on vegetation will be studied in the frame of the existent Pleistocene Park grazing experiment, which is conducted by the cooperative Northeast Science Station Cherskii to reconstitute a mammoth steppe like ecosystem experimentally at the lower course of the Kolyma River. The results of the Pleistocene Park experiment will be compared on the one hand with unaffected vegetation along the main, climatically controlled gradient from boreal forests to tundra and to relict steppe vegetation more inland in Yakutia as well as on the other hand with reconstructed Late Pleistocene palaeovegetation recorded in syngenetic permafrost deposits. Macroscopic plant remains are preserved in excellent condition in the permafrost section Duvanny Yar in close proximity to the Pleistocene Park experiment and will be used to reconstruct structure, composition and dynamics of the late Quaternary vegetation in NE-Siberia. Special focus will be devoted to the transition from the late glacial to the Holocene when mammoth fauna declined and the ecosystem restructuring in Northeast Siberia culminated. Interesting findings are also expected from the comparison of palaeovegetation during the last two interglacials: the Eemian (Kazantsevo), when vegetation was affected by megaherbivore grazing and the Holocene, when grazing held off. By combining both approaches, we will identify the relative proportions of climate and grazing as potential main drivers determining the characteristics of extant and Pleistocene vegetation in western Beringia.