依据吉木萨尔县泉子街乡桦树窝子和小西沟两个剖面进行高时间分辨率的孢粉分析,结合剖面岩性特征分析、历史文献记录和碳屑鉴定,揭示了天山北麓最近2000多年以来的环境变化。2000 a B.P.以前,该地植被为荒漠草原;2000~1300 a B.P.(50 a B.C.~650A.D.),植被为草原植被,其中1750~1400 a B.P.(200~550A.D.),植被为有少量森林的草原植被,当时气候状况较今凉湿,适宜云杉生长,使得云杉林带下移,幅度可达250m左右。当时的年均气温较今低1℃而降水量较高,是新疆历史上一个相对冷湿的环境;约1300~450 a B.P.(650~1500A.D.),植被为荒漠草原;450 a B.P.年以来,植被为荒漠草原-草原。

Based on the sporo-pollen analysis and ¹⁴C sample annual dating on the deposits of Huashuwozi section and Xiaoxigou section in the northern piedmonts of Tianshan Mts., together with lithologic analysis of the two sections and historic records, this article reveals the environment change during the last 2 000 years. With the thickness of 110 cm,the Huashuwozi section is divided into six layers and contains 52 sporo-pollen samples. The Xiaoxigouzi section is divided into seven layers and contains 38 sporo-pollen samples, with the thickness of 190cm. During the experiment, the spore pollens which belong to 45 families and genera are identified. The five collected ¹⁴C samples are determined by the librarian at laboratory of the Institute of Geology, China Seismology Bureau. Based on the sporo-pollen assemblage features of Huashuwozi section, four sporo-pollen assemblage belts are separated from top to bottom, which reflect that,from 2 000 a B.P., the vegetation has undergone a succession processes which is divided into four stages.,which are desert-steppe stage, steppe(forest-steppe) stage,desert-steppe stage and desert-steppe,steppe stage in proper order. 2 000 a B.P. ago, the vegetation in this place is desert-steppe; from 2 000 a B.P. to 1 300 a B.P., the vegetation was steppe. More interestingly, from 1 750 a B.P. to 450 a B.P., the steppe, associating with a small quantity of forests, was distributed dominantly. During this period,the temperature was relatively low and the humidity was comparatively high. Therefore, it was comparatively cold and humid in history in Xinjiang. The environment was good for the growth of Pecea asperata at this period of time. As a result, the Pecea asperata timberline declined at most about 250 m. From about 1 300 a B.P. to 450 a B.P., the vegetation was desert-steppe, which was similar to current situation. Since 450 a B.P., the vegetation has been desert-steppe and steppe with odd broad-leaved forest nearby. Birch forest has been in an advantageous position.The Pecea asperata timberline declined and the environment has been comparatively cold and humid.