Relationship Between Tree Species Diversity and Soil Ecological Biochemistry Characteristics in Urban Wetland: A Case Study of International Important Wetland in Hangzhou, China

Tree species diversity in forest ecosystems is crucial for maintaining ecosystem stability and functionality. However, its underlying mechanisms linking to subsurface ecological processes—such as soil nutrient cycling—remain unclear, particularly in urban wetland ecosystems. This study, conducted at Xixi Wetland, an internationally important wetland, also a typical subtropical urban wetland in Hangzhou, Zhejiang Province, China, analyzed the relationship between tree species diversity and soil ecometabolic ratios based on species diversity surveys. Results indicate that mulberry and paper mulberry dominate Xixi Wetland, with diversity indices comparable to other subtropical forests in China. Tree species diversity and soil physicochemical properties showed significant positive correlations with total soil nitrogen and organic carbon, but no significant effect on total phosphorus. Together, tree species diversity and soil physicochemical properties explained 65.88% of the variance in soil ecological–chemical ratios. Tree species diversity significantly influenced soil nitrogen cycling in Xixi Wetland but had limited effects on phosphorus cycling. Enhanced tree species richness not only promotes organic carbon accumulation in coarse aggregates, providing a scientific basis for wetland carbon sink management, but also maintains nutrient cycling stability by strengthening soil resilience to biotic disturbances. This holds significant practical value for ecological design in urban wetland parks. This study provides scientific support for managing subtropical wetland ecosystems.