Abstract: In order to investigate the distributive characteristics of soil nematode communities in Stipa breviflora desert steppe and to assess the effects of different grazing intensities on soil nematode communities, a systematic investigation on soil nematode communities in four test plots with different grazing intensities in Stipa breviflora desert steppe was conducted. A total of 7 200 nematodes per 100 g dry soil belonging to 18 genera were obtained in the test areas. The two genera of Acrobeloides and Acrobeles accounted for 22.78% and 41.90% of the total number of individuals, respectively, and they were the dominant genera in this region. Diversity analysis showed that the light grazing plot had higher number of individuals and species richness of nematode communities compared to the other grazing intensity plots. The highest community diversity index was observed in the control plot, followed by the light grazing plot, heavy grazing plot and moderate grazing plot. The community uniformity index was heavy grazing plot > control plot >（light grazing plot = moderate grazing plot）. The ecological index analysis revealed that the maturity index was light grazing plot > control plot > moderate grazing plot > heavy grazing plot, indicating that the soil of light grazing plot and control plot was more stable, while that of the heavy grazing plot was mostly prone to be disturbed by external activities. The highest channel index was observed in the moderate grazing plot, followed by the heavy grazing plot, light grazing plot and control plot. Furthermore, via multiple stepwise regression analysis between the environmental factors including plant community diversity, biomass, coverage, average height, dry weight of litter, soil moisture, soil pH value, soil organic matter and other environmental factors of plots with different grazing intensities and the community characteristic indexes, the key ecological variables that affected the soil nematode communities under grazing conditions were determined. Our results provide a reference for determining the grazing intensity that is beneficial to the maintenance of the biodiversity of nematode communities in desert steppe.

Key words: desert steppe；grazing intensity；soil nematode community