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