Bacterial network complexity drives carbon, nitrogen and phosphorus metabolism potential under short-term soil water content changes in wetlands

Abstract

Wetland soil microbial communities play pivotal roles in biogeochemical cycling; however, how their network complexity mediates carbon (C), nitrogen (N), and phosphorus (P) metabolism in response to soil water content (SWC) changes remains unclear. In this study, soil samples from the Zhalong, Momoge and Xianghai wetlands in Songnen Plain of China were incubated under natural (CK), drought (10 % SWC), and high SWC (50 % SWC) conditions, followed by metagenomic sequencing to evaluate the impact of SWC changes on bacterial community structure and function. The results showed that soil bacterial diversity and network complexity decreased under drought but recovered under high SWC, with Proteobacteria and Actinobacteria displaying divergent responses. C fixation pathways (rTCA and DC-HB cycles) were significantly enriched under 50 % SWC, which correlated strongly with enhanced bacterial interactions. The abundance of denitrification genes (norBC, nosZ) decreased under drought but increased under high SWC. P metabolism (purine metabolism and two-component systems) showed strong SWC dependence, with key genes (PstS, phnDC) increased in abundance under 50 % SWC. Notably, bacterial network complexity tightly coupled with metabolic pathways, indicating SWC driven community restructuring regulates wetland soil C, N and P cycling. These findings underscore the critical importance of hydrological management in maintaining bacterial-mediated nutrient cycling functions of wetland ecosystem under climate change.