[Characteristics of Soil Organic Carbon and Mineralization with Different Stands in Jinyun Mountain]

Soil organic carbon (SOC) is the largest organic carbon stock on land, and slight changes in SOC can significantly affect the atmospheric CO₂ concentration, among which forest soil carbon reservoir accounts for approximately 70% of the global soil carbon stock. Therefore, the implementation of efficient management for SOC stock in the forest ecosystem has become a popular research subject. The mineralized characteristics of SOC in different soil layers (0-20, 20-40,40-60, and 60-100 cm) were analyzed in five typical stands of Jinyun Mountain:broadleaf forest, coniferous forest, coniferous and broadleaf mixed forest, bamboo forest, and 15a abandoned grassland (control soils) in the study area. The results showed that forest type, cultivation duration, and soil depth had significant effects on the SOC mineralization rate. The mineralization rate of SOC in different forest stands decreased with the deepening soil layer, among which the mineralization rate at the 0-20 cm soil layer[11.97-25.12 mg·(kg·d)^-1] was significantly higher than that of other soil layers (P<0.05), and there were no significant differences between the mineralization rates of other soil layers[4.79-6.51 mg·(kg·d)^-1]. The accumulated mineralization of SOC in the five forests decreased with the deepening soil layer. The accumulated mineralization of SOC in the bamboo forest and broadleaf forest in the 0-20 cm soil layer was the highest at 177.66 mg·kg^-1 and 120.38 mg·kg^-1, respectively. With the deepening soil layer in the 60-100 cm soil layer, the accumulated SOC mineralization in the coniferous forest reached the highest (46.96 mg·kg^-1). The SOC mineralization process in the different stands of Jinyun Mountain can be well fitted by the double reservoir first-level kinetic equation. The content of easily decomposable SOC in different forest stands decreased with the deepening soil layer. Coniferous forest soil exhibited a stronger mineralization ability and higher utilization degree of refractory organic carbon stock, while bamboo forest and broadleaf forest soils had higher microbial activity, which could effectively promote the carbon cycle and improve the soil carbon fixation ability.