Mechanisms Behind the Soil Organic Carbon Response to Temperature Elevations

Soil organic carbon (SOC) represents the most dynamic component of the soil carbon pool and is pivotal in the global carbon cycle. Global temperature rise and increasing drought severity are now indisputable realities, making soil organic carbon cycling under climate warming a critical research priority. This review elucidates the mechanism of the SOC response to temperature increase in terms of both extrinsic and intrinsic factors. The extrinsic factors are temperature elevation methods, rainfall, and land use. Different methods of temperature increase have their own unique advantages and disadvantages. Indoor warming methods exclude other factors, making temperature the only variable, but tend to ignore carbon inputs. In situ field warming and soil displacement methods help researchers explore the response of the complete ecosystem carbon cycle to temperature increase but cannot exclude the interference of factors such as rainfall. Elevated rainfall mitigates the adverse effects of elevated temperatures on organic carbon sequestration. In addition, the response of SOC to temperature elevations vary among different land use types. The temperature sensitivity of SOC is higher in peatland (high organic matter) alpine meadows (colder regions). The intrinsic factors that affect the response of SOC to elevated temperatures are SOC components, microorganisms, SOC temperature sensitivity, and SOC stability. The SOC decomposition rate is influenced by variations in the ratios of decomposable (easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC), and microbial biomass carbon (MBC)) and stabilizing (inert organic carbon (IOC), alkyl carbon, and aromatic carbon) SOC to total organic carbon (TOC). Furthermore, temperature elevations also affect the soil microenvironment, resulting in microbial community reorganization such as changes in bacterial and fungal ratios and abundance. At the same time, soil aggregates, clay minerals, and iron and aluminum oxides protect the SOC, making it difficult to be utilized by microbial decomposition. The systematic clarification of the mechanism behind the SOC response to higher temperatures is crucial for accurately predicting and modeling global carbon cycles and effectively responding to the loss of SOC pools due to global temperature elevations.