浑善达克沙地湖相沉积记录的全新世植被和气候变化研究

The temporal and spatial patterns of the Holocene climate change of the marginal monsoon area on millennial and centennial scales, is of great significance to understand the evolution of the climate subsystems including the East Asia Summer Monsoon (EASM), the Asia Winter Monsoon (AWM) and the Westerly, and the coupling dynamics and the linkage between the tropic ocean, the arctic and the North Atlantic. Nevertheless, consensuses were still not reached possibly because that those published Holocene climate sequences in the marginal monsoon area were somewhat deficient on the age control, the sampling resolution and the geographic coherency. Therefore, this proposal aims at the high quality reconstructions of the Holocene vegetation and climate sequences of Otindag dune field of Inner Mongolia, the nature of the millennial and centennial scale climate change and the coupling dynamics and linkage between the tropic ocean, the arctic area and the North Atlantic area. Specifically, two lacustrine sediment sequences were retrieved in the center of two lakes using the UWITEC piston corer and age model were constructed on the base of the AMS 14C dating of the terrestrial plant residues and/or the organic matter. In case that no terrestrial plant residues could not be found, scientific appraises for potential carbon reservoir effect were made using the comparison with the 210Pb-137Cs dating for the top layer, the dates of occasional terrestrial plant residues, and the references of the dating of the water and/or the hydrophyte. On the base of the age-depth model, vegetation and climate sequence were reconstructed using the pollen, grain size, susceptibly and the geochemical proxies. Based on these two Holocene sequences and those published Holocene sequences, synthesis were conducted to explore the millennial and centennial scale climate pattern, and comparisons were made to disclose the coupling dynamics and linkage mechanisms with the tropic ocean, the Arctic area and the North Atlantic area. Furthermore, the vegetation responses to the climate changes during the Holocene were studied to provide analogs or references for the regulations of modern ecology.

季风边缘区全新世千年和百年尺度气候变化时空变化规律的揭示，对于理解东亚夏季风、冬季风和西风带气候系统演化历史及其与热带海洋（ENSO）、北极（AO）以及北大西洋（NAO）的作用过程和联系机制具有重要意义。然而，已有序列在年代控制、分辨率和地理分布等方面存在不足，阻碍了学界对上述问题的深入认识，亟待在该区域建立高质量的全新世植被和气候变化序列。为此，本项目以浑善达克沙地湖泊沉积物岩芯为研究对象，以陆源植物残体或全样有机质AMS14C年代和210Pb-137Cs交叉定年为框架，结合现代花粉-植被-气候关系研究，利用孢粉、粒度、磁化率、元素地球化学等代用指标高分辨率地定量重建浑善达克沙地全新世植被及气候环境变化序列，集成研究揭示季风边缘区全新世千年及百年尺度的植被和气候变化的时空分布规律，为认识全新世东亚夏季风演化和热带海洋、高纬度以及北大西洋的作用过程和联系机制提供帮助。

全新世东亚夏季风演化的时空差异及其对植被生态的影响是晚第四纪生态学关注的科学问题之一。浑善达克沙地位于我国北方季风边缘区，其全新世植被变化及生态响应等研究可为认识气候变化和植被响应等问题提供帮助。本研究选取浑善达克沙地北部查干淖尔湖和西南侧乌兰胡绍海子湖泊沉积物为研究对象，以AMS14C测年为框架，以区域现代过程研究为基础，利用孢粉、粒度和盘星藻等代用指标，高分辨率综合重建了上述区域晚冰期以来的植被、气候和沉积环境变化；结合非孢粉气候因子及人类活动影响因子序列，利用排序分析、敏感性分析等研究探讨不同植被类型对气候变化的响应，揭示人类活动对植被生态的影响。.研究结果表明，16 cal. kyr BP以前，浑善达克山地北部植被发育较少，可能为荒漠，西南侧山地为草原，气候干旱；16~11 cal. kyr BP，北部为半荒漠，西南侧山地发育桦木疏林草原，气候温凉、略变湿润；11.0~8.5 cal. yr BP北部为荒漠草原，西南侧山地为桦、榆疏林草原，气候渐变暖湿；8.5~6.0 cal. yr BP，北部为桦、榆疏林草原，西南侧山地为栎、榆、桦森林草原，气候最为温暖湿润；6.0~3.0 cal. yr BP北部植被退化为草原，西南部山地植被为稀疏松疏林草原，气候温暖偏干；3.0 cal. yr BP以来，北部地区为草原，其中0.34~0.11 cal. yr BP恶化为荒漠，西南部山地植被为草原。.区域集成研究表明，北方季风边缘区全新世东亚夏季风最盛始于~8.5 cal. kyr BP，与传统认识一致，终于~6.0 cal. kyr BP，早于传统认识，与石笋记录的南方夏季风衰退时间一致。 .排序分析和敏感性分析结果表明，山地栎、松、云杉林主要响应于年均温和年降水，降水增加可能促进栎林和松林扩张，温度增加可能促进云杉林向上扩张；桦木林响应于夏季温度变化，温度降低导致了桦木林的扩张；草原和荒漠扩张主要响应于夏季风（年降水），夏季风衰弱造成了草原和荒漠扩张；人类活动对山地森林影响有限。.研究结果丰富了我国北方全新世孢粉植被气候序列，为集成研究提供了资料；植被生态响应研究为认识将来变暖情形下区域植被变化预测提供了参考。