Stability Mechanism and Influencing Factors of Soil Organic Carbon

Purpose To provide theoretical support for the research and practice of soil carbon sequestration under the background of global climate change.

Methods The stability mechanisms (such as molecular structural resistance, aggregate physical protection, mineral chemical protection, and soil microbial carbon pump) of soil organic carbon (SOC) and its influencing factors (such as soil physicochemical properties, land use pattern, atmospheric CO₂ concentration, and burning) were reviewed.

Results Lignin and black carbon have complex molecular structure and strong anti-decomposition ability, but they can be degraded when the environment is suitable; the packaging of SOC by aggregates and the restriction on microorganisms reduce the decomposition probability of SOC, and the mineral-bound organic carbon formed by mineral adsorption can be stable in soil for thousands of years; arbuscular mycorrhizal fungi transport a large amount of plant-derived carbon to the soil, and the proportion of stable carbon transformed by microorganisms is up to 62% in SOC. The three mechanisms work together to improve the stability of SOC. SOC-related factors affect SOC input and output by changing vegetation composition and productivity, microbial community structure and activity, and suitable environment can promote SOC accumulation. However, the complexity of the ecosystem makes the response of SOC to the same factor in different sites may be different. For example, the effect of high CO₂ concentration on SOC is shown as promotion, inhibition, or no significant effect in different studies.

Conclusion The stability mechanism in soil prolongs the turnover time of SOC, and it is beneficial to the accumulation of SOC. Therefore, when exploring the impact of various factors on SOC, it is not possible to generalize, and a comprehensive analysis should be conducted in combination with the type of ecosystem.