新疆博斯腾湖地区全新世以来的孢粉组合与环境

THE ASSEMBLAGE OF HOLOCENE SPORE POLLEN AND ITS ENVIRONMENT IN BOSTEN LAKE AREA XINJIANG

本文通过对新疆博斯腾湖地区沉积物的孢粉分析，讨论了全新世以来的植被和气候变化的四个阶段，并结合其它沉积特征，反映了这一时期湖泊的水面的收缩和扩张的状况和自然环境的演变．

Bosten lake located at Yanji basin in the southern slop of the Tianshan Mountains.The paper presents results of pollen analyses on sediment of Holocene in which six pollenzones are defined. According to assemblage characteristic of spore-pollen, the vegetationchange was defined in four stage since Holocene: (1)In early-Holocene, the desert-steppevegetation mainly consist of abundant Artemisia, Chenopodiaceae, comositae and Gram-neae. (2) In early of middle-Holocene, the desert vegetation mainly consist of Chenopodi-aceae, Ephedra, Artemisia. (3) During the period from middle of middle-Holocene to ear-ly of late-Holocene, the desert-steppe vegetation mainly consist of Ariemisia, Chenopodiaceae and Compositae. (4) Since late-Holocene, the desert vegetation is mainly composedof Chenopodiaceae, Ephedra.Analysis result shown that the climate of Bosten lake area is arid since Holocene.During the period from middle of middle-Holocene to early late-Holocene. the climate isrelatively warm and humid.Since Holocene, under the influence of climate change, Bosten lake area expand orshrank many times. The expansion of Bston lake area show three kinds of situations: (1)Climate was humid and rain increased. (2) A period of temperature rising in which thevolume of melting snow and ice melting was increased and the water flowing into the lakewas increased. (3) A period of low temperature resulted in lake evaporation decreasing,and the lake area would be expending.Since Holocene, the valley forest and marsh meadow was confined in the banks ofrivers and convergence of the river with Bosten lake, the area of valley forest and marshmeadow depended on the water volume of rivers.