Environmental response to climate and human impact during the last 400 years in Taibai Lake catchment, middle reach of Yangtze River, China.

Element content, grain size, pollen and 210Pb dating analysis were performed on 80 cm sediment core from Taibai Lake, a shallow lake in the middle reach of Yangtze River in China, to reveal the response of catchment environment to climate changes and human activities during the past four centuries. The 210Pb dating suggests that 0-39.5 cm of the core represents the past 163 years and bottom of the core is at ca. 1590 AD. Major changes showed in the core are compared with the records from historical documents, including population, cultivation and climate etc. 1700-1810 AD was the period with intensive human activities in Taibai Lake catchment, behaving as deforestation and cereal cultivation expansion, signaled in the sediments by low percentage of pinus pollen and high percentage of Gramineae pollen, high content of <16 microm fraction. Another period with intensive human activities was since 1928 AD, behaving as deforestation, reservoir construction, land reclamation, soil loss. The high sedimentation flux epochs, such as 1900-1920 AD, 1931 AD, 1938-1939 AD and 1954 AD, were correlated with high precipitation; nevertheless, the high sedimentation flux epochs in 1958-1970 AD and 1983-1993 AD were correlated with the land reclamation around Taibai Lake and soil loss due to intensive cultivation development respectively. The two coldest stages during the "Little Ice Age" were in 1650-1700 AD and 1810-1900 AD, consistent with the historical records generally, characterized by weak weathering, high forest coverage and weak human activities in Taibai Lake catchment.