贵州白鹇湖沉积物记录的4～2kaB.P.干旱气候事件及其生态环境影响

DRY EVENT AT 4～2kaB. P. RECORDED BY THE SEDIMENTS OF BAIXIAN LAKE AND IT'S IMPACT ON THE REGIONAL ECO-ENVIRONMENT

喀斯特地区的生态环境具有先天脆弱性,对气候变化响应敏感,是研究气候变化-生态环境变化耦合关系的理想场所。选取我国典型喀斯特地区湖泊白鹇湖为研究对象,系统分析了沉积物柱芯有机质C/N比值、Sr/Rb比值和孢粉的剖面变化。研究结果表明,白鹇湖地区3.6～2.2kaB.P.气候持续向干旱化方向发展,导致流域陆地植被显著退化,草本植物减少,蕨类植物增加,湖泊陆源有机质输入减少,沉积物有机质C/N比值降低。该干旱事件还导致流域化学风化作用减弱,Sr/Rb比值增大。白鹇湖过去5000年的气候与生态环境变化历史表明自然气候变化对喀斯特生态环境可产生重大影响,为喀斯特生态环境先天脆弱性提供了历史性证据。

The karst region is sensitive to climate change because of its environmental vulnerability and thus becomes an ideal place to study the coupling process of changes in climate and eco-environment. Baixian Lake in south East Guizhou Province is a typical karst lake. A sediment core recovered from the lake was analyzed for organic C/N ratio, Rb/Sr ratio and pollen assemblage to understand the process of environmental changes in karst regions. During the period of 3.6 - 2.2kaB. P., the regional vegetation declined with decreasing herbs and increasing ferns, the input of terrestrial organic matter to the lake was reduced, and the C/N ratios of organic matter in the lake sediments decreased, indicating the drying of the climate. The Sr/Rb ratios of the core sediments were high during this interval, denoting the weakening of chemical weathering intensity in the lake basin. The history of changes in the climate and eco-environment of the Baixian Lake region over the last 5000 years suggests that the natural process of climate changes could have a key impact on the eco-environment of karst regions.