Human disturbance reshapes microbial controls on SOC stability in coastal blue-green spaces

Coastal blue-green spaces are critical ecological units for carbon sequestration. Under global warming, the effects of human disturbance intensity (HDI) on soil organic carbon (SOC) stability across diverse spatial structures-blue spaces (BS), green spaces (GS), and aquatic-terrestrial ecotones (ATE)-remain poorly understood. This study investigated typical HDI and aquatic-terrestrial gradients. Random Forest (RF) and Partial Least Squares Path Modeling (PLS-PM) were integrated to analyze the coupling of SOC, iron oxides, and microbial processes. The results showed that:(1) HDI significantly weakens ecosystem resistance to warming. High-disturbance areas exhibit elevated SOC content (8 g kg^-1 higher than low-disturbance areas in ATE) due to exogenous inputs, but show increased thermal sensitivity. The path coefficient of temperature on environmental factors reached 0.79. (2) ATE demonstrated superior buffering capacity against dual stressors (path coefficient = 0.22), compared to the climate-sensitive BS and disturbance-sensitive GS. This resistance was supported by a peak in microbial carbon use efficiency (CUE) under moderate disturbance and by a coupled regulation of iron, nitrogen, and microbial diversity that buffered thermal stress. Overall, this study elucidates how HDI and spatial heterogeneity jointly regulate microbial temperature sensitivity and carbon stability. These findings provide novel ecological evidence for coastal carbon cycle responses and support the optimization of urban blue-green space management for carbon sink enhancement.