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 Q (which is defined as the factor of change in mineralization with a 10 °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 Q. When carbon availability is not limited, Q is controlled by carbon quality; otherwise, substrate availability controls Q. A model driven by such quality-availability tradeoffs explains 97% of the spatiotemporal variability of Q in incubations of soils across the globe and predicts a global Q of 2.1 ± 0.4 (mean ± one SD) with higher Q in northern high-latitude regions. We further reveal that global Q 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.