Abstract: In order to investigate the changes of bacteria in surface soil during the early stage of grazing prohibition in the Stipa krylovii grassland,this study utilized high-throughput bacterial data and soil physicochemical property data from the Stipa krylovii grassland in Inner Mongolia from 2018 to 2020 to analyze the changes and mutual relationships of the surface bacterial community and soil physicochemical properties in the early transition from natural grazing to grazing prohibition. The results showed significant changes in the relative abundance of bacteria during the transition from natural grazing to grazing prohibition,however,there were no significant changes in the dominant bacterial species composition. Compared to 2018,the relative abundance of Actinobacteria and Proteobacteria increased in 2019,and in 2020,and the relative abundance of Proteobacteria exceeded that of Actinobacteria. Under natural grazing conditions,bacterial abundance and diversity were significantly negatively correlated with soil volumetric water content,while bacterial abundance was significantly positively correlated with soil temperature. In the early stage of grazing prohibition,bacterial abundance was significantly positively correlated with pH,soil organic matter,and soil temperature,while it was significantly negatively correlated with soil volumetric water content. Bacterial abundance was more influenced by grazing prohibition and soil physicochemical properties than bacterial diversity. Therefore,these results provided a theoretical basis for further research on the changes of bacterial communities in surface soil after grazing prohibition.

Key words: Stipa krylovii grassland, Grazing prohibition, Topsoil, Bacterial community, High-throughput sequencing

摘要： 为探究克氏针茅草原禁牧初期表层土壤细菌的变化情况，本文利用2018—2020年内蒙古克氏针茅草原的细菌高通量数据和土壤理化性质数据，对自然放牧向禁牧转变初期的表层细菌群落和土壤理化性质的变化及其相互关系进行分析。在自然放牧向禁牧转变初期，细菌相对丰度发生较大变化，但优势菌种组成没有显著变化，其中，相较于2018年，2019年放线菌门和变形菌门相对丰度均增加，2020年变形菌门相对丰度超过了放线菌门。自然放牧条件下，细菌丰度、细菌多样性均与土壤体积含水量存在显著负相关关系，细菌丰度与土壤温度显著正相关；禁牧初期，细菌丰度与pH、土壤有机质、土壤温度显著正相关，与土壤体积含水量显著负相关。细菌丰度比细菌多样性更容易受到禁牧和土壤理化性质的影响。因此，本研究结果为进一步研究禁牧后表层土壤细菌群落变化提供了一定的理论依据。

关键词: 克氏针茅草原, 禁牧, 表层土壤, 细菌群落, 高通量测序