Abstract: [Objective]Soil water content is a primary limiting factor in inland desert wetland ecosystems and plays a crucial role in maintaining ecological functions of the vegetation. Relationships between soil water content and other ecological characteristics were further studied to reveal the influence of soil water content on plant diversity distribution, in order to provide a theoretical basis for plant diversity conservation, restoration and sustainable management.[Method] Based on the basic survey of soil moisture, plant height, plant species and coverage at Dunhuang Xihu National Nature Reserve in Gansu, the characteristics of vegetation and soil properties were analyzed, and also the influences of soil water content on distribution pattern of plant diversity in the ecosystem were investigated.[Result]Overall, all indices of species diversity were relatively small, and the maximums of Shannon-Wiener, Margalef and Simpson indices were 1.38, 0.72,and 0.72, respectively;the averages of plant coverage, abundance, height and density were ranged from 39.26% to 70.19%, 15.50 to 80.11 plant·m^-2, 49.65 to 124.63 cm, 0.039 to 7.204 plant·m^-2,respectively. On vertical direction, the soil water content increased with soil depth across all sample sites and ranged from 3.87% to 41.23%, but changed little on the horizontal direction, for soil layers with depth of 0-60 cm, 60-200 cm and 0-2 m, the soil content ranged from 4.67% to 14.59%, 6.45% to 25.33% and 65.6 to 248.2 mm respectively. The effects of soil water content at deep layer on species diversity of trees and shrubs were higher than that of herbaceous, and the effects on species richness were larger than on abundance. Furthermore, a significant positive correlation was found between the soil water contents at deep layers and the species abundance. But the species diversity of herbaceous relied more on soil water contents at shallow layers, indicating a significant positive correlation between them. There was a significant positive correlation between soil water contents in each layer, also a significant positive correlations between water content in each soil layer with moisture storage in 0-2 m soil layer and plant coverage, but soil water contents in 0-80 cm layer had a negative effects on plant height and density. The soil water contents at all layers of 80-200 cm depth were positively related to plant height, and soil water contents storage at 0-2 m had a significant positive correlation with plant coverage, plant height and density. In addition, the plant coverage had a significant positive correlation with plant height and density, and there was a negative correlation between the plant height and density, but plant height was negatively related to plant density.[Conclusion]The species diversity indices of plant community and soil water contents were relatively smaller in the study area. The species diversity of trees and shrubs depended on soil water contents at deep layer, but herbaceous plants on shallow layer. The soil moistures in deep layer and 2 m depth may be the dominant factor affecting the vegetation characteristics. Different plant species and genera were inter-restricted and closely interacted with each other, but also independent from each other to a certain extent.

Key words: Dunhuang Xihu, desert and wetland ecological system, soil water contents, vegetation community characteristic, plant diversity