VEGETATION HISTORY OF THE WESTERN LOESS PLATEAU OF CHINA DURING THE LAST 40ka BASED ON POLLEN RECORD

In this paper, several pollen records from the Pleistocene(with resolution ranging from 200 to 300 years) and Holocene (resolution ranging from 20—300 years) loess profiles of Jingning, Dingxi, Qin’an, Gansu Province, were used to reconstruct the rapid changes of vegetation types including steppe, forest-steppe, conifer forest and desert steppe (or desert) across the western Loess Plateau over the past 40ka BP. Major features of the vegetation history in Jingning were the ebb and flow of forest and steppe. During the 44—29 ka BP (MIS3), conifer forest grew and the climate was temperate and humid; after 23 ka BP, the open steppe occupied the Jingning area, the climate was cold and dry, and the desert steppe expanded during the LGM. During the greater part of the Holocene, steppe or forest steppes developed. However, during the early and mid-Holocene ( 8.8? ?.8ka BP), the climate became relative humid. Thereinto, the most humid period was 7.6? ?.9ka BP, as suggested by the deveropment of forests. The steppe or open forest-steppe predominated and vegetation cover was sparse at other time during the Holocene, indicating a drier and colder climate condition. The general climatic conditions have become dry, while the vegetation transformed into desert steppes since 3.8ka BP. Overall, the climate was characterized by alternate drought and humid conditions and 11 drought events were recognised for the whole Holocene based on pollen records.