Spatial and temporal patterns of Holocene vegetation and climate changes in arid and semi-arid China

Pollen data from 30 sites in arid and semi-arid regions of China were reviewed to document regional patterns of Holocene vegetation and climate change and to understand the large-scale controls on these changes. Vegetation at most sites in eastern Inner Mongolia switched between forest, forest steppe, and typical steppe, showing maximum moisture conditions before 6 ka (1 ka 1⁄4 1000 cal yr BP) and a dry climate after 6 ka. Vegetation in the northwestern Loess Plateau changed between desert steppe, forest steppe and steppe, suggesting wet–dry oscillations, from an initial dry to wet climate at 9–4 ka and then back to a dry climate. In the northern Tibetan Plateau, vegetation was characterized by steppe desert, steppe or desert, indicating a wet climate in the early and mid-Holocene until 6–4.5 ka. In western Inner Mongolia and Xinjiang, pollen assemblages show changes between desert, steppe desert and steppe, with a wet period occurring during 8.5–5.5 ka at most sites. All the four regions show a drying trend during the late Holocene. The complex climate patterns suggest that regional climate responses to large-scale climate forcing were controlled by interactions of competing factors, including the monsoons, westerlies and topography-induced regional atmospheric dynamics. The role of human activity in vegetation change requires further investigation. r 2008 Elsevier Ltd and INQUA. All rights reserved.