Soil organic carbon stability under natural and anthropogenic-induced perturbations

Soil organic carbon (SOC) plays key roles in determining soil properties, plant nutrients, and land-atmosphere carbon exchange, yet is affected by various natural and anthropogenic perturbations such as wildfire, climate change, land use change and pollution. Herein, we review perturbation types and SOC response mechanisms, as well as new technologies to measure SOC stability, highlighting the resistance and resilience of SOC. Although there is great controversy on the nature and structure of SOC, it has been recognized that the SOC stability not only depends on physiochemical characteristics of SOC, but also on soil microenvironment, soil microbial community composition, and types of perturbations. Based on ecosystem stability theories, the change of SOC stability under perturbation can be keeping stable states, changing to an alternative stable states or system collapse. For future studies, we suggest that understanding responses of soil biogeochemical processes to multiple perturbations, well-designed experiments to quantify threshold and uncertainty of SOC, and integration of novel biological approaches besides physicochemical characterizations into SOC stability are needed. This review helps to better understand the process of SOC stabilization and reduce the uncertainties in assessments of global carbon stocks, not only for mitigating the effects of climate change through negative feedbacks but also for maintaining soil functions such as soil fertility, water quality, and resistance to erosion.