Late Holocene vegetation dynamic and human activities reconstructed from lake records in western Loess Plateau, China

A high-resolution pollen record from a mountain lake (2400 m a.s.l.) in the western Loess Plateau reveals variations of vegetation and human activities during the last 3200 years. The pollen record indicates the vegetation changes from mixed deciduous–coniferous forest dominated by Betula, Quercus, and Abies at 3200–2200 cal BP, to forest steppe co-dominated by trees (Betula, Quercus) and herbs (mostly Artemisia) at 2200–1100 cal BP and then to steppe-like vegetation since 1100 cal BP. A distinct vegetation type shift occurred at ca.1100 cal BP, accompanied by the increase of anthropogenic indicators (cereal-type pollen, Humulus-type pollen and Pediastrum). Human deforestation might have contributed to this abrupt shift. Micro-charcoal abundance also shows a generally increasing trend during the last 1000 years, suggesting enhanced human activities. After 1100 cal BP, two deforestation phases (1100–750 cal BP and 350 cal BP-present) and one forest expansion phase (750–350 cal BP) are identified. These phases have good correlation with historical events, suggesting that increased population pressures, flourished agriculture, and warfare are the main reason for these forest clearances. Anthropogenic activities appear to be the main controlling factor of the vegetation dynamics during the late Holocene, especially for the last 1100 years.