Spatial heterogeneity of temperature sensitivity of soil respiration: A global analysis of field observations

The temperature sensitivity of soil respiration (Q(10)) plays a key role in benchmarking the intensity of terrestrial soil carbon-climate feedbacks. However, there is large spatial heterogeneity of Q(10) that remains unexplained at the global scale. Here, we collected 480 estimates of Q(10) values from field studies to explore the spatial heterogeneity of Q(10) values and their controls at both global and regional scales. We used structural equation modeling to explore the direct and indirect factors and their relative importance predicting Q(10) values at the global scale, and in different ecosystem types (i.e. forests and grasslands) and climatic zones (i.e. tropical, subtropical, temperate, and boreal). We found that mean annual temperature (MAT) was the most important factor in predicting field Q(10) at the global scale, rather than mean annual precipitation (MAP) or soil properties (e.g. soil organic carbon (SOC) content). However, different dominant factors controlled Q(10) in different ecosystems and climatic zones. Across forests, MAT was the dominant factor except in the tropics, where Q(10) was mainly regulated by clay and SOC content. For grasslands, MAP, pH, and SOC were the most important factors in predicting Q(10). These findings indicate that global field Q(10) is mainly controlled by MAT, and this is inconsistent with most previous incubation experiments showing that soil properties are more important than climatic factors in predicting Q(10) values. Moreover, recognizing different dominant factors of Q(10) in different ecosystems and climatic zones improves our understanding of soil carbon-climate feedbacks in a warming climate.