Reconciling carbon quality with availability predicts temperature sensitivity of global soil carbon mineralization

Soil organic carbon (SOC) mineralization is a key component of the global carbon cycle. Its temperature sensitivity Q10 (which is defined as the factor of change in mineralization with a 10 degrees C temperature increase) is crucial for understanding the carbon cycle- climate change feedback but remains uncertain. Here, we demonstrate the universal control of carbon quality- availability tradeoffs on Q10. When carbon availability is not limited, Q10 is controlled by carbon quality; otherwise, substrate availability controls Q10. A model driven by such quality - availability tradeoffs explains 97% of the spatiotemporal variability of Q10 in incubations of soils across the globe and predicts a global Q10 of 2.1 +/- 0.4 (mean +/- one SD) with higher Q10 in northern high- latitude regions. We further reveal that global Q10 is predominantly governed by the mineralization of high- quality carbon. The work provides a foundation for predicting SOC dynamics under climate and land use changes which may alter soil carbon quality and availability.