贵州西部山地末次盛冰期以来植被演替与气候重建

The western Guizhou region locates in the eastern slope of Yunnan-Guizhou Plateau on the second landform ladder of China, within the western subtropical semi-humid zone, which is influenced by the Southwest monsoon (SM). Vegetation types and distribution patterns in this area are closely related to the SM. The mountain peat in this area records the process of paleeclimatic and paleonvironmental evolution since the Last Glacial Maximum (LGM), which provides an ideal research material for the better understanding of the evolution of subtropical vegetation during the LGM, the change characteristics and evolution rule of the SW. However, the paleeclimatic and paleoenvironmental reconstruction based on pollen in this region remains not enough to reveal the response progress of vegetation to monsoon climate during the LGM. Therefore, a continuous subalpine peatbog core, which was obtained from the Niangniangshan Mountain wetland in western Guizhou Province, will be chosen as the research material in this project. Integrated multi-proxies analysis of pollen, charcoal, grain-size, chroma, loss on ignition etc. will be conducted for the reconstruction of the time sequence of regional climate and environment change, and reveal the evolution characteristics of evergreen broad-leaved forest in this region since LGM. The response progress of vegetation to monsoon climate will be studied. Combined with modern pollen data, the annual mean temperature and precipitation since LGM will be reconstructed, and the vegetation type and the fluctuation range of climate change will be discussed. Comparing with the North Hemisphere solar insolation and the stalagmite records of the neighbored region, it may provide new evidence for the better understanding of the mechanism of SW and regional environment change as well as future climate prediction.

贵州西部地区位于我国第二级阶梯云贵高原东部斜坡，处于亚热带西部半湿润区，受西南季风影响，植被类型和分布格局与西南季风密切相关。该地区山地泥炭完整地记录了末次盛冰期以来古气候和环境演变过程，为深入理解亚热带末次盛冰期植被演替和西南季风在该区的变化特征以及演变规律提供了理想的研究材料。然而，目前利用孢粉恢复的古气候环境还不足以清晰地揭示该区末次盛冰期植被-季风气候的响应过程。因此，本项目选择贵州西部娘娘山亚高山泥炭钻孔作为研究对象，应用孢粉、炭屑、粒度、色度和烧失量等多气候替代性指标综合分析，建立区域气候环境演变的时间序列，揭示该地区常绿阔叶林在末次盛冰期的变化特征，研究植被的演替对季风气候的响应过程，结合表土孢粉数据，重建温度和降雨变化过程，探讨植被类型和气候变化幅度，并与北半球太阳辐射和邻近地区石笋研究结果对比，为更好地理解西南季风的变化机制和区域环境演化以及预测未来气候变化提供新的佐证。

末次盛冰期全球普遍降温，雪线下降，冰盖冰川大幅扩张，是地球历史上距现在最近的极端寒冷时期。我国亚热带地区植被体系受到末次盛冰期气温下降和季风减弱的影响，区域植被面貌发生了明显的改变，然而，关于我国亚热带地区植被类型和分布格局的认识，目前仍存在较大分歧；对该地区末次盛冰期气候干凉或冷湿的认识以及植被的变化和迁移过程—冰期季风降雨减弱而形成的草原-草甸的扩张是否取代了亚热带阔叶林，尚有争议。贵州西部地区位于我国第二级阶梯云贵高原东部斜坡，处于亚热带西部半湿润区，受西南季风影响，植被类型和分布格局与西南季风密切相关。为了揭示末次盛冰期植被对气候的响应，更好地理解西南季风的变化机制和区域环境演化以及预测未来气候变化提供新的佐证，本文通过对云贵高原东部斜坡贵州西部山地泥炭钻孔岩芯进行AMS14C定年以及孢粉、炭屑、粒度、色度和烧失量等多气候替代性指标综合分析。研究结果表明：在MIS3晚期（ca. 36-21 cal ka BP），当地建群种以壳斗科和桦木科等温带树种为主的落叶-常绿阔叶林，伴生少量松和铁杉为主的针叶林和以杜鹃科为主的灌木，林下草本则以禾本科（Poaceae）和莎草科（Cyperaceae）为主，表明此时气候偏凉，但区域气候依然湿润。LGM（ca. 21-16 cal ka BP）期间，孢粉组合特征表现为以栎属（Quercus.D）和榛属（Corylus）为代表的温带落叶阔叶林含量占据绝对优势，反映北亚热带地带性植被落叶阔叶林空间上向南转移，林下草本依然是以禾本科为主，但并未出现草原植被的扩张，而水生草本莎草科（Cyperaceae）几乎消失，表明该区域气候进一步干冷。 冰消期由落叶阔叶林过渡至以栎属（Quercus.D）、榛属（Corylus）和栲属/石栎属（Castanopsis/Lithocarpus）等树种组成的落叶-常绿阔叶林，表明常绿阔叶林扩张北移，气候逐渐回升变暖。贵州西部山地泥炭钻孔孢粉记录的末次盛冰期植被演替和气候变化表明，该区域末次盛冰期植被的演替主要表现为落叶阔叶林的扩张和收缩，气候经历了凉湿-干冷-凉湿，总体上与北半球低纬度夏季太阳辐射呈现良好的对应关系。