A review of the factors influencing soil organic carbon stability

Increasing soil carbon sequestration is an effective measure to deal with global climate change. As an important carbon sink, soil organic carbon (SOC) is a critical medium for carbon sequestration. In recent decades, the molecular structure of SOC has been identified as the most important element in predicting SOC cycle. However, new studies have proven that the recalcitrance of the molecular structure of organic carbon limits the determination of SOC stability in the soil. Also the interaction between SOC and the surrounding environment significantly limits the possibility of degradation of SOC. Soil micro-organisms influence SOC cycle not only through decomposing, but also through microbial products which are the primarily components of SOC. Abiotic factors including inorganic soil particles, inorganic soil environment and nutrient conditions directly or indirectly control SOC dynamics. Among these factors, adsorption to soil minerals and occlusion within soil aggregates have been determined to strong support the long-term stability of SOC. The role of minerals in SOC adsorption and stability depends on the mineralogy and chemical property of SOC. Soil aggregates not only physically protect SOC from mi-crobial and enzymatic attack, but also promote the adsorption of SOC to minerals. On the contrary, organic mineral complex can also combine with other inorganic or organic materials to form aggregates so that SOC adsorbed to minerals can be further occluded by aggregation. Therefore, SOC adsorption to minerals and occlusion within aggregates complement each other. Moreover, inorganic environment (e.g., temperature and moisture) also acts on SOC dynamics. Put together, we suggest that the persistence of SOC was mainly due to complex interactions between SOC and the surrounding environment, including micro-organism, reactive mineral surfaces, soil aggregates, temperature, water and nutrient. Meanwhile the biochemical property of SOC also depends on environment conditions. However, whether the inherent quality of SOC or its surrounding environment is an ecosystem property; and each property affects and interacts with each other. Therefore, the persistence of SOC is a specific property of ecosystem that integrates each property.