Simulated Warming Alters Soil Nutrient Dynamics Through Microbial Community Shifts During Wetland Plant Litter Decomposition

Plant litter decomposition drives soil biogeochemical cycling, yet how warming alters interactions among litter quality, microbial communities, and soil C, N, and P transformations remains unclear. We conducted a 90-day soil microcosm incubation at 15, 25, and 35 °C using single and mixed litter of Calamagrostis angustifolia and Carex lasiocarpa from the Xingkai Lake wetland to assess warming effects on decomposition, microbial communities, and C, N, and P dynamics. Warming significantly accelerated decomposition, with the highest decomposition constant observed for mixed litter at 35 °C. Mixed litter showed greater temperature sensitivity at 25–35 °C, whereas decomposition rates were weakly correlated with initial litter C/N, C/P, and N/P ratios. Warming and decomposition time reshaped microbial communities, with bacterial diversity increasing over time and fungal diversity declining at 35 °C. Despite accelerated mass loss, C, N, and P dynamics remained asynchronous, with net C release in some treatments, net N accumulation, and litter-dependent P responses. Three-way ANOVA, RDA, and partial least squares structural equation modeling were used to examine associations among environmental factors, microbial attributes, litter decomposition, and soil C, N, and P status. Overall, warming modifies relationships among litter quality, microbial communities, and C, N, and P transformations, providing insights into freshwater wetland responses to climate warming.