Tree species and urban green space types jointly drive rhizosphere SOC fractionation and stability via microbial-enzymatic pathways

Soil organic carbon (SOC) dynamics in urban ecosystems are critically influenced by vegetation-microbe interactions, yet how tree functional types and green space management jointly regulate rhizosphere SOC fractionation and stability remains poorly understood. Here, we investigated the divergent effects of two native tree species,Populus tomentosa (deciduous broadleaf) and Pinus tabuliformis (evergreen conifer),across four urban green space types (urban parks, residential areas, roadside shelterbelts, and suburban forests) on rhizosphere SOC stabilization pathways. By integrating extracellular enzyme stoichiometry, microbial community assembly, and SOC fraction analyses, we identified carbon (C) and phosphorus (P) availability as the key limiting factors for microbial metabolism in both species.