Effects Of Grazing Intensity On Soil Physicochemical Properties And Bacteria Diversity For Stipa Baicalensis Steppe In Inner Mongolia

Overgrazing was the main driving force of grassland degradation. Studing the effects of grazing on soil physical and chemical characteristics and soil microbe to reveal the ecological effects of grazing could provide the theoretical evidence for the grassland management. In this paper, Stipa baicalensis steppe was the research object, the response of soil bacterial diversity and soil physical and chemical properties to grazing was researched by field survey and laboratory analysis, theory and methods of modern ecology, and modern Biotechnology PCR-DGGE, which provided scientific basis for grassland degradation mechanism and reasonable utilization. The main conclusions were as follows:1. With the increase of grazing intensity, soil water content, soil organic carbon content, soil total phosphorus content, the radio of C/N reduced and the pH value increased. Total nitrogen content was highest under moderate grazing, and it was lowest under heavy grazing. The response of the soil physical and chemical properties to grazing was more intense in 0-10cm soil layer. Over-grazing caused a negative impact on soil physical and chemical properties, and reduced the quality of soil.2. Under grazing, soil bacterial diversity was rich in Stipa baicalensis Steppe. The results suggested that the bacterial community in Stipa baicalensis steppe soil mainly consisted ofα-,β-,γ-,δ-Proteobacteria, Gemmatimonadetes, Actinobacteria, Verrucomicrobia, Chloroflexi, Firmicutes, Acidobacteria, Bacteroidetes and Nitrospirae. The dominant groups are Proteobacteria and Gemmatimonadetes. The Verrucomicrobia was detected only in the moderate-grazing soil sample.3. Soil bacterial diversity in 0-10cm soil layer was higher than that in 10-20cm. The soil bacterial diversity pattern significantly changed with the increase of grazing intensity. The diversity index of soil bacterial in 0-10cm were 2.90, 3.16, 2.74 and it was 2.73, 2.81, 2.33 in 10-20cm under light grazing, moderate grazing and heavy grazing, respectively. Soil bacteria diversity was higher in moderate grazing than the other grazing intensities, which consisted with intermediate disturbance hypothesis.4. The Canonical Correspondence Analysis showed that soil bacterial community diversity, grazing intensity and the soil physical and chemical properties were closely related. There was a close correlation between bacterial community diversity and soil organic carbon, C/N under light grazing. And there was a close correlation between bacterial community diversity and total nitrogen under moderate grazing. Under heavy grazing, soil bacterial diversity related with soil pH value.