Abstract: Microorganisms play a crucial role in biogeochemical cycling and energy flow in freshwater lake wetland ecosystems, and are important component for the maintenance of wetland ecosystem function. In this study, we analyzed soil bacterial and archaeal composition in the top-five largest freshwater lake wetlands in China, by 16S rRNA gene sequencing. The distance decay relationship, redundancy analysis, Mantel test, variance partitioning analysis and co-occurrence analysis were used to investigate the variations of bacterial and archaeal community assembly and their co-occurrence. The results showed that under the co-driven geographical and climatic factors (site longitude and latitude, altitude, and mean annual precipitation) and soil physical and chemical factors (pH, total organic carbon, ammonium, and nitrate), the bacterial and archaeal communities of the five freshwater lake wetlands showed significant biogeographic distribution pattern. The dominant common species and the taxa structuring a modular co-occurrence network were those with the function of methanogenesis, methane oxidation, sulfate reduction, and nitrification, which are interdependent or competitive in the wetlands. Despite the biogeographic differences, soil microbial communities from the five largest freshwater lake wetlands harbored a tightly associated holistic network in their ecosystem functions.

Key words: freshwater lake wetland, biogeographic distribution, distance-decay relationship, co-occurrence network.