Baixian Lake in Southeast 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 3.6～2.2 ka B.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 5 000 years suggests that the natural process of climate changes could have a key impact on the eco-environment of karst regions.
