[Bacterial Community Structure and Functional Characteristics of Soil in Tussock Marsh Wetland with Different Degradation Levels].

To explore the characteristics and influencing factors of soil bacterial communities in degraded marsh wetlands, we divided the tussock marsh wetland in northeast China into three degradation degrees： non-degraded （ND）, mildly degraded （LD）, and heavily degraded （HD）. High-throughput sequencing technology and PICRUSt bacterial function prediction tools were used. We analyzed the soil environmental characteristics and soil microbial community structure characteristics of degraded wetlands and explored the influencing factors of microbial changes in degraded wetlands. The results showed that： ① The soil pH value was generally neutral to alkaline in general. With increasing degrees of degradation, the contents of soil organic carbon, total nitrogen, total carbon, and zinc decreased significantly （0.05）, while the content of total potassium increased significantly （0.05）. ② The dominant bacterial groups included Proteobacteria, Acidobacteriota, and Gemmatimonadota in the degraded wetlands. ③ The Alpha diversity of soil bacterial communities increased significantly with the increases in wetland degradation degree （0.05）, and there was a significant difference between degraded （LD and HD） and non-degraded （ND） wetlands in bacterial community composition.④ From the perspective of bacterial community functions, the primary metabolic functions, such as metabolism, genetic information processing, cellular processes, and environmental information processing, were significantly weakened with the increasing degree of degradation （0.05）. The main secondary functions such as amino acid metabolism, carbohydrate metabolism, biodegradation, and metabolism of exogenous substances were significantly weakened （0.05）. ⑤ Pearson correlation analysis showed that the change in soil bacterial Alpha diversity was significantly correlated with the contents of soil total nitrogen, total carbon, and organic carbon and the physical characteristics （diameter, height, and number） of hummocks （0.05）. RDA results showed that pH value was a key factor affecting soil bacterial community structure in the degraded wetland （0.05）. The functional differences of bacterial communities were mainly affected by the contents of soil total iron and zinc （0.05）. In conclusion, soil physical and chemical properties, bacterial community diversity and structure, and bacterial community function changed regularly with the degree of degradation. Soil pH； contents of total nitrogen, total carbon, and organic carbon； and physical characteristics of tussock were the key factors affecting the microbial community in the degraded wetland, which can provide the scientific basis for understanding the degradation and restoration processes of marsh ecosystems.