Lake sediment records on climate change and human activities in Xingyun Lake catchment, Yunnan Province, China

Sediments from Xinyun Lake, which lies in the middle of Yunnan Province, have recorded the environment history since the Holocene. With the application of multi-proxy indicators (e.g. grain-size, CaCO3 and chi lf, as well as AMS 14C datings, we identified three major climatic stages over the Holocene. In paticular, during 10.52-9.08 cal. ka B.P., the lake catchment was characterized of increased rainfall and relatively warm and humid climate. As a result the lake level expanded gradually indicating an intensified southwest monsoon. We also have examined the impact of human activities in the past 2000 years. Paleolimnological results revealed a strong increase in magnetic susceptibility and a rapid decrease in median grain size of lake sediments around 620 AD, with a relatively stable state afterwards. These indicated an intensified surface runoff and expansion of agricultural lands in the catchment. This is in good agreement with documentary records, which showed expansion of population and intensified human activities since early Tang Dynasty in the central area of Yunnan. Our study clearly showed that long-term human activities and land cover change have strongly impacted the evolution of lake environment and therefore modulated the control of regional climate in central Yunnan.