<b>Variation in Soil Microbial Nutrient Limitation and Carbon Use Efficiency and Their Driving Mechanisms in Riparian Wetlands</b>

Ecoenzymatic vector angles in the riparian wetlands were consistently greater than 45°, indicating that soil microorganisms generally experienced strong potential P limitation, whereas vector length and CUE varied significantly among plant communities. Random forest and piecewiseSEM analyses showed that vector length, the microbial biomass carbon‑to‑nitrogen ratio, the soil organic carbon‑to‑total nitrogen ratio, dissolved organic carbon, bulk density, and vector angle were key predictors of CUE.

CUE was jointly regulated by soil nutrients, microbial biomass, and extracellular enzyme activity patterns. Extracellular enzymes exerted a strong direct effect on CUE, whereas soil nutrients exerted a strong indirect effect through microbial biomass and extracellular enzymatic processes. This study advances our understanding of the mechanisms regulating microbial metabolism in riparian wetlands under hydrological fluctuations and provides an important theoretical basis for accurately evaluating the soil carbon sequestration potential of wetlands.</p>