Abstract: Distribution patterns of biodiversity at large scale and their affecting factors are one of the focal issues of ecology. Xinjiang is located in an extremely arid area in northwest China, where there are ideal places to explore the distribution patterns of species richness and their affecting factors under extreme conditions because of the complicated topographical and climatic conditions and the diversity of habitats. In this study, the relationships between the distribution patterns of species richness of vascular plants and the climatic factors in Xinjiang are analyzed based on the available data of vascular plants and climatic factors. The results reveal that the species richness increases with the increase of annual precipitation (AP) and actual evapotranspiration (AET), and the curve of species richness of vascular plants with the increase of MAT and PET is unimodal. In all the subregions, species richness increases significantly with AP. Species richness patterns with the increase of MAT are different in the mountains and basins, it increases at first and then decreases with the increase of MAT in mountains, but decreases monotonically in the basins. At different water deficit (WD) levels, the increase rate of species richness is decreased with the increase of AP at high WD. Species richness increases with the increase of MAT at low WD level but decreases at high WD level.

Key words: annual precipitation (AP), mean annual temperature (MAT), potential evapotranspiration (PET), water deficit (WD), vascular plant, species richness, Xinjiang