Based on modern pollen studies and reliable chronology of nine AMS 14C dates, a detailed history of vegetation and climate changes during the past 8660 cal. a BP was reconstructed by a high-resolution pollen record from Ugii Nuur in central Mongolia. Poaceae-steppe dominated the study area and the climate was mild and semi-humid before 7800 cal. a BP with a noticeable cool and humid interval at 8350―8250 cal. a BP. Xerophytic plant increased and the climate became warm and dry gradually since 7800 cal. a BP. From 6860 to 3170 cal. a BP, semi-desert steppe expanded, suggesting a prolonged warm and dry climate. Between 3170 and 2340 cal. a BP, regional forest steppe expanded whereas semi-desert steppe retreated, indicating the climate became cool and wet gradually and the humidity reached the maximum at the end of this stage. From 2340 to 1600 cal. a BP, a general cool and wet climate prevailed. And the climatic instability increased after 1600 cal. a BP. Review of regional pub-lished palaeoclimatic records implies that the mid-Holocene dry climate might have prevailed in vast areas from central Mongolia to arid areas of northwest China. Pollen-based climate reconstruction for UG04 core was well correlated with the result of climate model on Central Asia by Bush. In addition, several abrupt climatic events (cool and wet) were found and some could be broadly compared with the cool events in Atlantic.
WANG WeiMA YuZhenFENG ZhaoDongMENG HongWeiSANG YanLiZHAI XinWei
A pollen record from Haiyuan section in the southern part of Ningxia revealed a detailed history of vegetation variation and associated climate changes during the period from^13.0 to^7.0 14 C ka BP.A steppe landscape under a moderately dry(and probably cool)condition(~12.7-~12.1 14 C ka BP)was replaced by a coniferous forest dominating the landscape under a generally wet climate from^12.1 to ~11.01 4C ka BP.This generally wet period,corresponding to the European B?lling/All?rod period,can be divided into three stages:a cool and wet stage between^12.1 and^11.4 14 C ka BP,a mild and rela- tively dry stage between^11.4 and^11.2 14 C ka BP,and a mild and wet stage between^11.2 and^11.0 14 C ka BP.The coniferous forest-dominated landscape was then deteriorated into steppe landscape (~11.0-~10.6 14 C ka BP)and further into a desert steppe landscape from^10.6 to^9.8 14 C ka BP,being correspondent to the European Younger Dryas period.After a brief episode of a cool and wet climate (~9.8-~9.6 14 C ka BP),a relatively mild and dry condition prevailed during the early Holocene(~9.6- ~7.6 14 C ka BP)and then a warm and humid climate started the mid-Holocene(~7.6-~7.2 14 C ka BP).
