Contrasting Abiotic and Biotic Controls on Spatial Patterns of Soil <scp>C:N:P</scp> Stoichiometry in a Subtropical Karst Forest

ABSTRACT Mechanistic insights into the drivers of soil carbon (C), nitrogen (N), and phosphorus (P) stoichiometry are essential for optimizing forest management strategies. This study investigated the influence of biotic factors (including plant diversity and structural attributes) and abiotic factors (including site and topography) on the spatial variability of soil C, N, and P concentrations and their stoichiometric ratios, utilizing field data from a 25‐ha subtropical karst mixed evergreen–deciduous broadleaf forest plot. The results indicated mean soil C, N, and P concentrations of 61.33 ± 0.83, 7.03 ± 0.12, and 1.60 ± 0.03 g kg −1 , respectively, demonstrating moderate spatial variability with coefficients of variation (CV) ranging from 33.87% to 47.50%. The average stoichiometric ratios were 9.40 ± 0.14 for C:N, 53.70 ± 1.82 for C:P, and 6.15 ± 0.22 for N:P, exhibiting more pronounced spatial heterogeneity with CVs between 35.79% and 88.18%. Random forest analysis identified soil depth as the primary driver of soil C, N, and P contents, while elevation emerged as the most significant driver of C:P and N:P ratios. Multiple linear regression and generalized additive models confirmed that rock outcrop ratio and woody plant height diversity positively influenced soil C, whereas soil depth had a negative effect. Variance partitioning analysis revealed that site factors explained 6.8% and 9.9% of the spatial variation in soil C and N, respectively, while topographic factors explained 12.2% of the variation in soil P, as well as 8.3% and 5.4% of the variation in C:P and N:P ratios, respectively. Collectively, our findings reveal strong spatial heterogeneity in soil nutrients and stoichiometry, shaped by interactions among topographic, site, and vegetation factors. This study provides critical insights for forest conservation and restoration strategies in subtropical karst ecosystems.