Variations in the diversity of the soil microbial community and structure under various categories of degraded wetland in Sanjiang Plain, northeastern China

Abstract Understanding the changes in microbial community composition in wetlands affected by different types of degradation can help enrich theoretical knowledge about wetland degradation. However, studies of the relative role of microorganisms under different types of degradation of wetlands are rare in wetland ecology. Because of agricultural development, a large volume of groundwater has been extracted from the Sanjiang Plain over the last few decades, which has caused wetland degradation. To provide information for the development and protection of this wetland ecosystem, investigations into the processes of wetland degradation are important. The aim of the present work was to assess the impacts of wetland degradation on soil microbial communities under four different types of wetlands degradation in the Sanjiang Plain: swamp meadow (SW), meadow wetland (MW), paddy farmland (PF), and cropland (CL). Both 16S and ITS rRNA gene amplicon sequencing were used to evaluate the diversity and composition of bacteria and fungi. A total of 638,758 effective 16S rRNA and 916,211 valid internal transcribed spacer rRNA gene sequences were obtained, which were classified into 11 fungal and 40 bacterial phyla. The dominant fungal and bacterial phyla were Ascomycota and Proteobacteria, respectively. In addition, wetland degradation increased the relative abundances of Chloroflexi and Gemmatimonadetes, but the relative abundances of Proteobacteria and Verrucomicrobia significantly decreased. The bacterial Shannon index of SW was lower than those of the other investigated sites. Fungal diversity showed no significant differences for different types of degraded wetlands. In addition to wetland degradation, different reactions of the dominant microbial phyla and their diversity were clearly coorelated with total phosphorus (TP), total potassium (TK), available potassium (AK), and soil organic matter (SOM), which formed essential criteria that influenced the soil microbial communities. Wetland degradation resulted in the decrease of soil nutrient and the decline of the abundance of dominant phylum in soil bacterial and fungal communities. These changes can be used as an early warning signal for the degrading wetland of the Sanjiang Plain.