Soil Organic Carbon Stability and Its Controlling Factors in Typical Permafrost Wetlands in the Great Hing’an Mountains, Northeast China

The stability of soil organic carbon (SOC) in high-latitude permafrost regions plays a critical role in the global carbon balance. However, a systematic understanding of SOC pool fractions and their response to warming across different wetland types in the Great Hing’an Mountains remains lacking. In this study, soil samples were collected from forested, shrub, and herbaceous wetlands at depths of 0–60 cm and incubated at 5, 10 and 15 °C. A three-pool first-order kinetic model was employed to analyze SOC mineralization characteristics, carbon pool fractions, and influencing factors. The results showed that SOC mineralization rates exhibited a pattern of rapid increase followed by a peak and gradual decline over time, decreased with soil depth, and increased with temperature. The mineralization potential followed the order of shrub wetlands > herbaceous wetlands > forest wetlands. The temperature sensitivity (Q 10 ) was lowest in the deep soil layer of shrub wetlands (1.2), whereas a deeper soil layer of forest wetlands exhibited the highest Q 10 value (3.5). Across the three wetland types, SOC was dominated by the inert carbon pool (61–72%), with forest wetlands showing the highest proportion of inert carbon (72%). The active carbon pool in shrub wetlands was most sensitive to warming, while herbaceous wetlands had the largest inert carbon stock. Soil pH was significantly negatively correlated with the inert carbon pool, whereas soil moisture content showed a significantly positive correlation. Path analysis further revealed that SOC had the largest total effect on inert carbon accumulation, whereas available nitrogen and pH showed the strongest direct associations with Q 10 . Wetland type was indirectly associated with inert carbon stocks through its influence on soil moisture, pH, SOC, and available nitrogen. These results highlight that both direct and indirect pathways jointly influence SOC stability in permafrost wetlands. Overall, Wetland type and soil physicochemical properties jointly regulate SOC stability and its response to warming. These results suggest that although forest wetlands possess stronger carbon stability, their stable carbon pools may become increasingly vulnerable under climate warming.