Abstract: To elucidate the impacts of cadmium pollution on soil microorganisms, soil samples were collected from lightly and moderately cadmium polluted farmlands in Zhuzhou of Hunan Province. This study analyzed the variations of bacteria, fungi and archaea communities, assessed the effects of soil physicochemical properties on soil microbial community structure, and explored the variation of soil microbial networks by network analysis. The results showed  cadmium pollution significantly altered the alpha diversity indices of bacteria and archaea, but did not significantly affect the alpha diversity indices of fungi. There were significant differences in microbial community structure between lightly and moderately cadmium polluted farmlands. Soil pH, total cadmium (Cd_T), available cadmium (Cd_A), available phosphorus (AP), and microbial biomass carbon (MBC) significantly affected bacteria and archaea, while fungi were mainly affected by pH, Cd_T, Cd_A, nitrate nitrogen (NO₃^-), and ammonium nitrogen (NH₄⁺). Co-occurrence network analysis revealed that moderate cadmium pollution reduced the number of connections, average node degree, and graph density in the microbial co-occurrence network, indicating that increased cadmium pollution affects interactions between microbes and reduces the complexity of microbial networks.

Key words: cadmium, rice field, high-throughput sequencing, microbial community structure, co-occurrence network analysis