荒漠草原土壤细菌群落对放牧强度变化的响应

[Objective]Due to the characteristic social economy and historical culture,the rough grazing has led to prominent grassland ecological problems in northern China,which have not been completely solved.Soil microorganisms are the most important structural and functional components of underground ecosystems,its community structure and diversity could reflect regional ecosystem stability and soil quality.In order to clarify the effects of different grazing intensity on soil physicochemical properties and bacterial communities.[Method]The grazing intensity regulation experiment was carried out in the desert steppe of Inner Mongolia Autonomous Region,four grazing intensities were set,namely the enclosure control group(CK),light grazing,moderate grazing and heavy grazing.Field investigation and 16S rRNA sequencing were used to compare and analyze soil bacterial community structure characteristics and their correlations with soil nutrient factors under different grazing intensities.[Result]A total of 4746 OTUs were obtained and identified in 36 phyla,95 classes,116 orders,206 families and 277 genera,(1)The Shannon,Simpson and Pielou indices of the light grazing group were significantly higher than the CK(P<0.05),and the moderate and heavy grazing groups were lower than CK,but the difference was not significant(P>0.05),and there was no significant difference in the Chao1 index among them(P>0.05);(2)Acidobacteria,Actinobacteria,Proteobacteria and Chloroflexi were the main dominant bacterial phyla;(3)Except for soil organic matter and available potassium,which had a significant negative correlation with the Shannon index(P<0.05),other soil factors had no significant correlation with soil bacterial diversity.(4)The contents of soil organic matter,total phosphorus,alkali-hydrolyzed nitrogen,available phosphorus and available potassium played a major role in the differences of soil bacterial communities with different grazing intensities.[Conclusion]Grazing could change the soil physical and chemical properties and affect the soil bacterial community composition and structure in desert steppe.Light grazing could improve the soil bacterial diversity and increase the input of soil available nutrients,while medium and heavy grazing could inhibit it.From the perspective of soil microbial characterization,long-term closure would not be the best choice for ecosystem restoration in desert steppe,and rational grazing control could effectively promote ecosystem material circulation,maintain biodiversity and improve ecosystem stability.