Effects of Forest Types on Soil Particulate Organic Carbon Contents and Distribution Along a Subtropical Climate Transect in China

The influence of various types of forests on the storage of C in forest soil is significantly more concerned in recent decades, as these ecosystems are crucial for mitigation of the effects of global climate change. Nevertheless, uncertainties remain surrounding the impact of different forest types on the stability and distribution of SOC. The influence of forest types on the content and distribution characteristics in CPOC, FPOC, MAOC fractions. Importantly, we found that the forest types significantly affect the content of SOC (p = 0.020), POC (p < 0.001), and MAOC (p < 0.001), there was a significant forest type × region interaction effect (SOC: p = 0.019, POC: p = 0.025, and MAOC: p = 0.003). The random forest analysis showed that FPOC and MAOC were the main factors affecting SOC which indicated FPOC and MAOC have higher relative importance to SOC. The subtropical forests POC and MAOC storage and distribution are driven by separate environmental factors. POC storage in subtropical forests is mainly controlled by exogenous C inputs and soil transformation processes, while subtropical forests’ MAOC storage is primarily controlled by constraints on C inputs and C stabilization mechanisms. Different environmental factors result in forest types with faster decomposition rates having more C stored in the total soil C pool in the MAOC. Altogether, this research emphasizes the importance of different forest types to SOC pools and provides valuable information for the distribution and stability of SOC fractions in different forest types.