干旱区生态环境知识资源中心

Fifty-six surface pollen samples from different vegetation zones in the Yili Basin, western Tianshan Mountains, Xinjiang were analyzed to examine the relationships between the surface pollen assemblages and the original vegetation. A pollen analysis and a vegetation investigation with a discriminant analysis show that the pollen assemblages greatly differ across disparate vegetation zones. Twelve pollen taxa can be used as significant types for vegetation reconstruction in the basin. These taxa were the most abundant in the surface pollen samples. Cupressaceae pollen percentages were greater than 1% in Cupressaceae shrubs. More than 5% of Picea pollen indicates the growth of a Picea forest within 5 km. The subalpine meadow that is distributed widely in the basin is characterized by high content of Artemisia, Chenopodiaceae, Poaceae, Picea, Asteraceae, Taraxacum and Arenaria pollen types. The Artemisia-Chenopodiaceae-Poaceae-Cannabaceae pollen assemblages indicate the presence of montane steppe in the area. Artemisia and Chenopodiaceae pollen dominate the desert steppe and Populus forest. Artemisia pollen percentages were greater than 60% in the Artemisia desert, whereas Chenopodiaceae pollen percentages exceeded 65% in the Chenopodiaceae desert. The Artemisia/Chenopodiaceae (A/C) ratios reflect the vertical moisture changes in the Yili Basin. The mean A/C ratios were greater than 1.2 in the subalpine meadow and montane steppe that occupy the humid zone in the basin. These ratios were between 1 and 1.2 in the Cupressaceae shrubs, desert steppe, Populus forest and floodplain meadow. The ratios were less than 0.5 in the Chenopodiaceae desert, which is an arid environment.