草原退化是草原生产力维持面临的一个重大挑战,这一过程显著影响着草原生态系统的能量流动和土壤养分变化过程,进而直接或间接地影响着土壤微生物.我们的研究目的 首先是调查不同草原退化程度(即未退化、中度退化和严重退化)如何影响着内蒙古温带草原的土壤微生物组成、多样性和功能,其次是阐明哪些生物和非生物因素导致了这些变化.我们的研究主要通过高通量测序技术分析土壤微生物的群落组成,并且采用FAPROTAX工具和FUNGuild工具分别预测细菌群落和真菌群落的功能.研究发现:草原退化显著降低了土壤细菌的多样性,但对真菌多样性影响不大.地下生物量、土壤有机碳和总氮与细菌的多样性变化呈显著正相关关系.草原退化显著增加了绿弯菌门的相对丰度(由2.48％提高到8.40％),降低了厚壁菌门的相对丰度(由3.62％降低到1.08％).其次,草原退化也显著增加了球囊菌门的相对丰度(从0.17％提高到1.53％),降低了担子菌门的相对丰度(从19.30％降低到4.83％).致病菌的相对丰度在草原退化过程中显著下降.此外,草原退化对土壤细菌群落的功能有显著的影响,尤其是与土壤碳氮循环相关的土壤细菌群落.我们的结果表明,土壤细菌群落对草原退化的响应比真菌群落更敏感.“,”Aims Grassland degradation represents a major challenge in the maintenance of grassland productivity.This process has dramatic impacts on energy flows and soil nutrient dynamics,thus directly or indirectly influencing soil microbes.Here,we aim to (i) examine changes in soil microbial composition,diversity and functionality in response to different levels of grassland degradation (i.e.non-degraded,moderately and severely degraded)in a temperate grassland in Inner Mongolia,and (ii) elucidate biotic and abiotic factors that are responsible for these changes.Methods The composition structureofsoil microbial community was determined by high-throughput sequencing.The functionality of bacterial communities was examined using the tool of FAPROTAX,and functional guilds of fungal communities were quantified using the FUNGuild pipeline.Important Findings Grassland degradation significantly decreased soil bacterial diversity but it did not affect fungal diversity.Belowground biomass,soil organic carbon and total nitrogen were positively related to changes in diversity of bacterial community.Grassland degradation significantly increased the relative abundance of Chloroflexi (from 2.48％ to 8.40％) and decreased Firmicutes (from 3.62％ to 1.08％) of bacterial community.Degradation also significantly increased the relative abundance of Glomeromycota (from 0.17％ to 1.53％) and decreased Basidiomycota (from 19.30％ to 4.83％) of fungal community.The relative abundance of pathogenic fungi (Didymella and Fusarium) was decreased significantly by degradation.In addition,degradation had a significant impact on putative functionality of soil bacteria related to soil carbon and nitrogen cycling.Our results suggest that soil bacterial community is more sensitive than fungal community in response to degradation in the temperate grassland.