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
利用AMS14C测年,结合地层沉积物特点,对中亚哈萨克斯坦南部Valikhanov黄土-古土壤沉积剖面进行孢粉浓度分析。沉积地层自下而上分为4个孢粉带(V1~V4),V1带蒿属花粉浓度高于其它种属;V2带孢粉种类丰富多样而且稳定;V3带总孢粉浓度比前面带段增加,草原成分的草本植物花粉浓度变化剧烈;V4带总孢粉浓度尤其是藜科和麻黄花粉浓度迅速大幅增加。揭示了中亚干旱区28000年以来植被和气候演化历史:28~1814C ka B.P.,植被是以蒿为主的干草原,气候寒冷并且偏湿润;18~1014C ka B.P.,植被为蒿属植物占绝对优势的温带草原,气候偏湿润;10~514C ka B.P.,植被为蒿-藜沙漠草原,气候干旱;514C ka B.P.以后,植被为藜-蒿草原,气候湿润。
以9个AMSHC年代为框架，以现代花粉研究为基础，UG04孔高分辨率孢粉记录重建了蒙古国中部8660 a BP以来的植被和气候变化：7800 a BP以前研究区植被以草原为主，气候温和略湿润，其中8350～8250aBP气候凉湿；7800～6860 a BP旱生植物增加，气候转向暖干；6860～3170 a BP半荒漠草原扩张，气候持续暖干；3170～2340 a BP旱生植被退缩，远山森林草原发育，气候转凉变湿，末期湿度条件达最佳；2340～1600 a BP气候较凉湿；1600 a BP以来气候波动较大，与区域古气候记录对比表明，蒙古国中部到中国西北干旱区可能存在持续干旱的中全新世气候。重建结果与GCM气候模式模拟结果有较好的呼应。此外，UG04孔孢粉记录揭示了若干气候变冷事件，部分可与北大西洋地区对应，但表现为冷湿。
