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

Abstract

The temperature sensitivity of soil respiration (Q10) plays a key role in benchmarking the intensity of terrestrial soil carbon-climate feedbacks. However, there is large spatial heterogeneity of Q10 that remains unexplained at the global scale. Here, we collected 480 estimates of Q10 values from field studies to explore the spatial heterogeneity of Q10 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 Q10 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 Q10 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 Q10 in different ecosystems and climatic zones. Across forests, MAT was the dominant factor except in the tropics, where Q10 was mainly regulated by clay and SOC content. For grasslands, MAP, pH, and SOC were the most important factors in predicting Q10. These findings indicate that global field Q10 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 Q10 values. Moreover, recognizing different dominant factors of Q10 in different ecosystems and climatic zones improves our understanding of soil carbon-climate feedbacks in a warming climate.