[Comparison of Soil Bacterial Community Structure Between Paddy Fields and Dry Land in the Huixian Karst Wetland, China]

In order to explore the effect of land-use change on soil bacteria in wetland systems, the topsoil (0-20 cm) of a natural wetland (NW), paddy field (PF), and dry land (DL) were collected in the Huixian karst wetland. The α-diversity, species composition, and abundance of soil bacterial communities were analyzed using high-throughput sequencing. The effect of environmental factors on bacterial community structure was also examined. The results showed that the soil bacteria in the Huixian karst wetland can be divided into 49 phyla and 145 classes. The Shannon index of bacteria in the PF was significantly higher, and the Simpson index of bacteria in the NW is significantly lower, than in the other two land-use types. The dominant phyla (operational taxonomic units, OTUs>1%) in the NW were Proteobacteria (52.15%), Actinobacteria (15.16%), and Acidobacteria (8.80%); the dominant phyla in the PF were Proteobacteria (45.79%), Acidobacteria (17.20%), and Chloroflexi (11.75%); the dominant phyla in the DL were Proteus (51.42%), Acidobacteria (15.51%), and Chloroflexi (7.43%). The dominant classes (OTUs>1%) in the NW were α-Proteobacteria (17.98%), β-Proteobacteria (13.72%), and Actinobacteria (13.13%); the dominant classes in the PF were Acidobacteria (14.35%), β-Proteobacteria (13.37%), and δ-Proteobacteria (12.02%); the dominant classes in the DL were α-Proteobacteria (19.44%), Formobacteria (13.30%), and Acidobacteria (13.03%). Among the dominant OTUs (>0.3%), the dominant genera of in the NW were Sphingomonas (OTU2, 59), Micromonospora (OTU5, 24 and 50487), Gemmatimonas (OTU1), and Tenotrophomonas (OTU8); the dominant genera in the PF were Lysobacter (OTU4 and 115) and Aquabacterium (OTU33); the dominant genera in the DL were Sphingomonas (OTU85, 157 and 2916), Rhodanobacter (OTU19 and 52), and Penlobacterium (OTU60). A heatmap showed that there were significant differences in soil bacterial community structure among the three land-use types. Redundancy analysis showed that pH, soil organic carbon (SOC), total nitrogen (TN), alkali-hydrolyzable nitrogen (AN), exchangeable Mg²⁺, exchangeable Ca²⁺, soluble organic carbon (DOC), and available phosphorus (AP) were the main factors that affected the bacterial community structure in the Huixian karst wetland. These results indicate that changes in land-use types have significantly shaped the structure of soil bacterial communities in this area.