天山南坡小尤尔都斯盆地表土孢粉初步研究

Study of the Surface Sporo-pollen in the Small Yourdusi Basin on the Southern Slopes of the Tianshan Mountains

通过天山中部小尤尔都斯盆地南北方向采集的27个表土样品的孢粉分析,探讨了孢粉和植被带的关系及盆地中美天鹅湖的孢粉来源问题.结果表明:孢粉组合主要成分是云杉属、菊科、禾本科、蒿属、藜科、唐松草属、莎草科、水龙骨和其他蕨类孢子,表土孢粉组合与各植被带之间有良好的对应关系.主成分分析表明,研究区植被分布主要受温度因素控制.上升气流和水流是影响针叶林带云杉属花粉传播的主要因素,由山谷风从巩乃斯云杉林带来的云杉花粉受到美天鹅湖北侧小山阻挡,沉降在湖泊以南的山坡上,之后随降雨和雪山融水进入美天鹅湖.大部分表土孢粉属种的空间分布与相应的植物分布一致,而蒿属和藜科花粉百分含量在一定程度上代表了区域花粉雨的信号,利用A/C比值重建古环境时须要谨慎.蒿、藜花粉计数较少时,A/C比值波动较大,计数值大于约280粒时,A/C比值趋于稳定.

27 samples were collected from a north-south transect in the Small Yourdusi Basin in the Central Tianshan Mountains,Xinjiang Region,in order to reveal the relationship between sporo-pollen and vegetation zones and the sporopollen sources in the Meitiane Lake in the basin.It is found that sporopollen assemblages are mainly constitute of Picea,Compositae,Poaceae,Artemisia,chenopodiaceae,Thalictrum,Cyperaceae,Polypodiaceae and other fern spores.There is a good correspondence between the surface sporo-pollen assemblages and the zones of vegetation.The principal component analysis also demonstrates that the distribution of vegetation is primarily controlled by temperature.The major factors that influence the dispersal of Picea pollen are the uplifting air current and stream.The Picea pollen is carried by the valley winds upwards and southwards from the Picea schrenkiana forest in Kunes River basin to the north of the Meitiane Lake,and then blocked by the hills adjacent to the lake.As a result,Picea pollen deposits on the slopes to the south of the lake,and then runs downwards into the lake by rain water and melt water.Specially,most pollen taxa are in accordant with the distribution of their relevant plant types.Pollen percentages of Artemisia and Chenopodiaceae may represent the mixed signal of regional pollen rain to some extent.It is found that A/C ratio fluctuates when small amounts of Artemisa and Chenopodiaceae are counted,whereas it is relatively stable when a total of more than 280 grains are counted.This is worth to pay attention to as reestablishing palaeoenvironment by A/C ratio.