Soil carbon, nitrogen, and phosphorus stoichiometry in subtropical forests of Zhejiang, China

Soil carbon (C), nitrogen (N), and phosphorus (P) stoichiometry in regional forests has garnered significant attention, yet reported distribution patterns and variation often show discrepancies and even contradictions. This study investigated soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) stoichiometry in the forests in Zhejiang Province, China, a region that defies conventional latitudinal vegetation zonation, using a systematic grid-based sampling approach across 122 plots. Mean topsoil SOC, TN, TP contents were 40.70, 2.68, and 0.36 g kg−1 respectively, with C:N, C:P, N:P ratios of 15.24, 145.90, and 9.26, indicating sufficient C and N supply but relative phosphorus deficiency. Both SOC content and C:N ratio exhibited non-linear trends with latitude, initially decreasing and then increasing beyond a turning point at 29°N due to systematic grid-based soil sampling in Jinqu Basin with warmer conditions, which is different to global and China’s forests. TP content increased and C:P ratio decreased monotonically with latitude, which supports the soil substrate age hypothesis. Concurrently, SOC and TN contents, as well as C:P and N:P ratios, increased with elevation. These patterns were primarily driven by soil properties, with climate and forest types acting as "dual triggers". Specifically, soil C and N stoichiometry was strongly influenced by climate, while soil P was more associated with forest types, revealing a "dominance-divergence" dual regulatory mechanism. These findings help us to rectify biases in global or large-scale models with overlooking regional heterogeneity and the divergent regulatory roles of climate and vegetation on soil stoichiometry.