[Spatial Distribution Characteristic Sand Influencing Factors of Soil Carbon and Nitrogen in Typical Subtropical...

To investigate the spatial variability of surface soil carbon and nitrogen content and determine the primary factors influencing their distribution in mountainous and hilly regions， Qingliangfeng National Nature Reserve was selected as the research area. Multiple analytical methods were employed， including semi-variance models， Kriging spatial interpolation， correlation analysis in SPSS， and structural equation modeling （SEM）. The results demonstrated that： ① The surface ω（SOC） in the study area ranged from 29.99 to 75.66 g·kg^-1，ω（TN） from 0.67 to 3.07 g·kg^-1， and the carbon-to-nitrogen ratio （C/N） from 16.34 to 64.10， all exhibiting moderate variability. ② Global Moran's I index revealed that SOC distribution exhibited highly significant spatial autocorrelation （P<0.01）， whereas TN and C/N ratio showed significant spatial autocorrelation （P<0.05）. Spatial distribution maps indicated that SOC and TN contents gradually decreased from high- to low-altitude zones， while the C/N ratio displayed an opposite trend. ③ Integrated correlation analysis， random forest analysis， and SEM indicated that soil carbon and nitrogen contents were primarily influenced by elevation， slope gradient， soil nutrients， and vegetation type. Specifically， SOC and TN were substantially positively correlated with elevation and vegetation type （P<0.01） but considerably negatively correlated with slope gradient （P<0.01）. Soil nutrients also exerted a significant negative effect （P<0.05）. In conclusion， increasing elevation induced vegetation zone succession to slow microbial decomposition of litter and reduced soil phosphorus and potassium contents. Simultaneously， vegetation demand for soil carbon and nitrogen was decreased in the low-temperature environments， which promoted the accumulation of SOC and TN. The results were able to offer a theoretical framework for reserves to optimize the sustainability of their ecological structure and functions.