Protection mechanisms and influencing factors of soil organic carbon pools in the Larix gmelinii forests

•The unprotected SOC pool is the largest in the Larix gmelinii forests soils.•Physical-chemical and chemical protected SOC pools tended to be saturated.•Unprotected and physical protected SOC pools are still not saturated.•Soil depth presented stronger effects on the SOC pools than forest age and type.•Soil physicochemical properties were crucial for SOC sequestration of each pool. The stability and dynamics of soil organic carbon (SOC) pools in forest soils are crucial for assessing and predicting the effectiveness of forest carbon sequestration. Various factors such as soil depth, nutrients availability, crustal elements, pH, and stand characteristics (tree type, tree age) influence the stability of SOC pools. To better understand SOC stability of cold temperate forest soil, soil samples were collected from 0–10 cm, 10–20 cm, 20–40 cm, and 40–60 cm depths in a Larix gmelinii forest. Then, the distribution characteristics of SOC pools under different protection mechanisms and their influencing factors were examined. Our results showed that the unprotected SOC pool was the highest, while the physical–chemical protected SOC pool was the lowest. Total organic carbon (TOC) had a linear positive relationship with unprotected and physical-protected SOC pools, and a logarithmic positive relationship with physical–chemical protected and chemical-protected SOC pools. Soil depth was the predominant factor affecting the SOC pools of each protection mechanism. The physical–chemical protected SOC pool significantly differed from forest types and forest ages, and the chemical-protected SOC pool was associated with the synergistic effects of forest age and type. Furthermore, soil moisture and acidity, and the crustal elements may play prominent role in the variation of SOC pools in the Larix gmelinii forests. Our findings suggested that the silt- and clay-associated SOC pools in the Larix gmelinii forest soils had approached or achieved saturation, while more organic C was fixed in the relatively active unprotected SOC pool. This unprotected pool was more sensitive to ecosystem change, indicating its importance in assessing forest carbon sequestration. Our study provided insights into the active and dynamic SOC pools in forest soils and their responses to different environmental factors. These findings can be utilized to accurately assess the carbon sink potential of cold temperate forest soils and inform the management of forest ecosystems.