Abstract: This study investigated plant community species composition and biodiversity in grazed Seriphidium semidesert grassland, to explore the relationship between community structure and environmental factors. The results showed that: 1) Grazed grassland had an obvious grazing gradient by sheep, and the utilization of grassland was reasonable. A detrended correspondence analysis revealed eight plant communities in the grazed area. There were significant differences in species diversity indexes among plant communities, and there was heterogeneity among communities; 2) Six environmental variables (soil organic matter content, amount of feces, grazing intensity, litter biomass, altitude, and slope direction) were chosen by forward selection. The first axis of a detrended canonical correspondence analysis showed gradients of organic matter content, amount of feces, and grazing intensity, while the second axis showed gradients of litter biomass, altitude, and slope direction gradient among communities. The plant species and communities were distributed along gradients of environmental factors. Our results show that quantitative ecological methods provide more detailed information about ecological relationships between vegetation and the environment for grazed Seriphidium semidesert grassland.

Key words: Seirphidium semidesert grassland, grazing, community diversity, DCCA (detrended canonical correspondence analysis) ordination