黔西山地末次冰期以来的植被迁移与气候变化

The mountain area in west Guizhou belongs to the subtropical plateau monsoon climate zone. The vegetation type in this region not only affected by high altitude vertical gradient zone but also controlled by the Indian monsoon, so the regional vegetation ecosystem is sensitive corresponded to the climate change. Despite there are some current studies related to pollen-vegetation-paleoclimate in southwest area, the lack of high-resolution pollen sequence research in regard to the edge of Yunnan-Guizhou plateau makes it hard for us to reveal the dynamic process of paleovegetation-paleoclimate since the last glacial maximum (LGM). In addition, the major pollen type in Yunnan-Guizhou plateau are Pinus and Quercus during the glacial period whereas it is difficult to identify the morphological characteristics in species level of these two types, and hence the indicative significance of paleoecology still remains ambiguous. In this project, core sediment from Caohai area, western Guizhou were selected, combining detailed studies of pollen analysis and scanning electron microscopy(SEM) to reconstruct the evolution of paleovegetation since last glacial period in research area, especially to conduct further research about population and ecological characteristics in Pinus and Quercus that appeared during glacial period. Meanwhile, pollen-based quantitative climate reconstruction from the modern surface pollen database in southwest China allows us to probe into the periodic changes of environment and climate change events. Finally, this work can also provide new proof for monsoon evolution mechanism as well as the biodiversity in southwest area.

贵州西部山区地处亚热带高原，其植被类型不仅受高海拔垂直梯度带的影响，同时深受西南季风的控制，区域内植被生态系统对气候变化具有敏感地响应。目前，尽管西南地区孢粉-植被-古气候已有一些研究，但云贵高原边缘区的黔西地区仍缺乏贯穿末次盛冰期的高分辨率孢粉序列，难以清晰的揭示末次盛冰期以来古植被-古气候的动态过程。此外，云贵高原盛冰期孢粉种类常以松属和栎属为优势，但其花粉类型以往缺少种一级形态特征鉴别，难以准确捕捉古生态的真实指示意义。本项目选择贵州西部草海地区钻孔沉积物为研究对象，利用孢粉分析等方法，拟定量恢复末次盛冰期以来的古植被演替过程，特别对盛冰期出现的松属和栎属花粉采用扫描电镜等方法进行种群及生态特征的进一步研究。同时利用西南地区现代表土孢粉数据，定量重建不同气候因子的变化规律与升降幅度，揭示气候环境的周期性变化以及短尺度快速气候事件，为西南地区生物多样性、季风演变机制等研究提供新的依据。

亚洲季风区降水的冰期-间冰期变化及其驱动机制一直是学术争论的焦点。尽管存在洞穴δ18O记录，但它们作为东亚夏季降水的替代指标仍受到质疑，目前没有替代的定量证据来验证这些记录。本研究利用基于花粉的定量气候重建，基于亚洲季风域的研究地点，证明了末次冰期-间冰期循环中气候经历了相对较大的变化。末次冰期和全新世暖期之间的降水量差异可能高达35% - 51%，年平均气温差异可能达到5°C - 7°C。我们的研究结果还揭示了H1和YD期间的区域异质性，这些事件导致中国西南部以印度夏季风为主的干旱条件，以及中国中部东部的湿润气候。重建降水的变化模式表现出强烈的冰期-间冰期变化，与中国西南部和南亚的石笋δ18O记录基本一致。我们的重建结果量化了MIS3降水对太阳辐射的敏感性，并强调了半球间温度梯度对亚洲季风变率的显著影响。与瞬态模拟和主要气候强迫相比，从末次冰期到全新世过渡期间的降水变率模式除了日晒强迫外，还受到大西洋经向翻转环流事件的显著调节。