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 °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.