摘　要：土壤细菌群落在草地生态系统土壤碳、氮养分代谢和循环过程中发挥着关键作用。本研究以关帝山林区3种典型退化草地群落类型为研究对象，选用高通量测序技术测定其土壤细菌群落组成及生物多样性，采用QIIME软件、R语言和ANOVA方差分析对数据进行统计和分析。结果表明：不同退化程度草地群落类型土层间土壤细菌群落组成及α多样性差异性显著；重度退化的苔草草地（CS）表层土壤细菌α多样性最高，利用和降解土壤有机质能力的芽单胞菌门（Gemmatimonadetes）和节杆菌属（Arthrobacter）的丰度值也最高；草地土壤中反硝化细菌是重要的优势菌群，其丰度含量随草地退化程度增加而显著增高；土壤细菌群落可通过降解土壤有机质和土壤反硝化作用，导致草地土壤有机质含量降低和土壤氮素流失，进而加速草地的退化。本研究结论为阐明关帝山林区草地退化主要成因和开展相关生态恢复与保护工作提供了重要的科学依据。
关键词：关帝山林区；退化草地；细菌群落组成；生物多样性；优势菌群

Abstract: Soil bacterial communities play a critical role in the metabolism and cycling of soil carbon and nitrogen in grassland ecosystem. Here, we selected three typical degraded grassland community types in Guandi Mountain forest region and determined soil bacterial community composition and biodiversity using high-throughput sequencing technology. Data were analyzed with using QIIME, R software and ANOVA analysis. The results showed that soil bacterial community composition and alpha diversity were significantly different among different degraded grassland community types and soil layers. Heavy degraded Carex stenophylloides grassland (CS) top-soil had higher in soil bacterial alpha diversity and abundance of Gemmatimonadetes phylum and Arthrobacter genus that can decompose soil organic matter. Soil denitrifiers as important dominant taxa in grassland soil and its abundance increased with the aggravation of soil degradation. Soil bacterial community can reduce soil organic matter content and prompt soil nitrogen loss by decomposed soil organic matter and denitrification process, and to accelerate grassland degradation. This study can provide an important scientific basis for elucidating the main reason of grassland degradation and implementing the corresponding ecological restoration and protection works in the Guandi Mountain forest region.
Key words: Guandi Mountain forest region; degraded grassland; bacterial community composition; biodiversity; dominant flora