[Effects of grazing on spatial distribution relationships between constructive and dominant species in Stipa breviflora desert steppe].

The effects of grazing on spatial distribution relationships of constructive species (Stipa breviflora) and dominant species (Cleistogenes songorica and Allium polyrhizum) in the desert steppe were analyzed by different analysis methods. The results showed that the landscape characteristic of S. breviflora + C. songorica + A. polyrhizum community was mainly affected by soil properties and inherent properties of populations. The spatial distribution variability influenced by continuous grazing (CG) was in order of A. polyrhizum > C. songorica > S. breviflora. The influence of CG upon the density of S. breviflora and A. polyrhizum was notable, while little influence upon the density of C. songorica was observed. S. breviflora density increased with the increasing C. songorica density in CG area, whereas it increased firstly and then decreased with the increasing C. songorica density in enclosed area (CK). S. breviflora density decreased with the increasing A. polyrhizum density in CG and CK area. It was concluded that there was density effect for plant interspecific relationships which could disappear with the presence of outside interference. Plant interspecific relationships were multiple with the difference in populations or interference conditions.