Environmental change in Bashang region historical periods.

The Bashang region is a typical vulnerable eco-environmental zone. Our analysis of paleodunes, paleosol profiles, and lake changes taking place during last ten thousands years indicated that: (1) 10-6.9 ka B.P. was a post-glacial temperature-increasing stage, in which lakes had their high water level; (2) 6.9-3.0 ka B. P. was a large warm stage, during which four paleosol layers were developed and climate fluctuation has assumed 4-5 small cold-humid and cold-dry alternations. Since 5.4 ka B.P., the lakes tended to gradually shrink; and by 2.1 ka B.P., water level has fallen by 2.7 m; (3) since 3.0 ka B. P. a general trend of the region was to change into a dry, warm-dry and cold-dry environment.