Flooding dominates soil microbial carbon and phosphorus limitations in Poyang Lake wetland, China

Soil microbial metabolic limitations influence the equilibrium between microbial metabolic requirements and the accessibility of soil substrates and nutrients. Although extensive research has examined the effects of hydrological regime changes on soil microbial activity and community structures, our understanding of their effects on soil microbial metabolic limitations remains inadequate. In this study, we quantified and evaluated soil microbial metabolic limitations along a flooding duration (FD) gradient over a three-year period in the Poyang Lake wetland, China, using vector analysis of extracellular enzyme stoichiometry. Our results revealed that the lengths and angles of the vector analyses ranged from 1.32 to 1.58 and 56.82° to 65.19°, respectively, across all samples, indicating that soil microbial metabolism was primarily limited by C and P. Both the vector length and angle showed negative correlations with FD, suggesting that microbial C and P limitations significantly decreased with increasing FD. Flooding regime primarily affected microbial C and P limitations through direct effects, as well as indirect effects resulting from plant features (e.g., plant community diversity, biomass, and nutrient properties) and soil nutrient ratios. Among hydrological, vegetational, and edaphic variables, flooding was the dominant driver of microbial C and P limitations. Overall, our research highlights the importance of hydrological regimes in regulating soil microbial metabolic limitations and provides valuable perspectives for understanding and predicting soil C and nutrient cycling in floodplain wetlands.