Abstract: PCR-DGGE technique was applied to study the effects of grazing on the community structure of soil bacteria in Stipa baicalensis steppe. Under the conditions of grazing, the bacterial community in 0-20 cm soil layer in the steppe was mainly consisted of α-, β-, γ-, and δ-Proteobacteria, Actinobacteria, Gemmatimonadetes, Chloroflexi, Firmicutes, Acidobacteria, Verrucomicrobia, Bacteroidetes, and Nitrospirae and among which, Proteobacteria and Actinobacteria were the dominant groups, while Verrucomicrobia was only detected in the soil under moderate-grazing. Canonical correspondence analysis showed that the soil bacterial community was closely correlated with grazing intensity and soil physical and chemical properties. Under light grazing, the bacterial diversity had a close correlation with soil organic C and soil C/N; under moderate grazing, there was a close correlation between bacterial diversity and soil total N; while under heavy grazing, the bacterial diversity was correlated with soil pH.

Key words: Imidacloprid, Arthropod community, Tobacco field