Mechanism underlying temperature sensitivity of soil organic carbon decomposition: A review

Temperature sensitivity (Q₁₀) of soil organic carbon (SOC) decomposition is an important index to estimate the dynamics of soil C budget. However, the spatial variation of Q₁₀ and its influencing factors remain largely uncertain. In this study, we reviewed the effects of climate environment, spatial geographic pattern, soil physicochemical property, vegetation type, microbial community composition and function, and global climate change on Q₁₀ to summarize the general rule of each factor influencing Q₁₀ and compare the relative contribution of each factor to Q₁₀ in different ecosystems. The results showed that Q₁₀ decreases with the increases of temperature and precipitation, but increases with the rise of latitude and altitude. The Q₁₀ value is higher in grassland than that in forest, and also in coniferous forest and deciduous forest than that in evergreen broad-leaved forest. Carbon quality is negatively correlated with Q₁₀, but the C quality hypothesis is not always valid with exogenous substrate input. For example, the increment of substrate availability may significantly increase Q₁₀ in low-quality soils. Q₁₀ decreases with the enhanced proportion of r-strategy microorganisms (Proteobacteria and Ascomycetes), but increases with the enhanced proportion of K-strategy microorganisms (Acidobacteria and Basidiomycetes). Q₁₀ increases with elevated CO₂ concentration, but declines with atmospheric nitrogen deposition. In natural ecosystems, Q₁₀ is mainly regulated by temperature and C quality. Temperature is the main factor regulating Q₁₀ in the topsoil while C quality is the main factor in deep soil. Our review provided a theoretical support to improve the coupled climate-C cycle model and achieved the C neutral strategy under global warming.