Temperature-Dependent Iron–Peroxidase Interactions Control Soil Carbon Stabilization across Climatic Gradients

Stabilization of microbial extracellular enzymes by iron minerals is a critical control on soil organic carbon (SOC) dynamics, yet the response of these interactions to climate warming remains poorly understood. Here, we investigated mineral–enzyme feedbacks along a 4000 km climatic transect (2–24 °C) and identified that peroxidase activity is sensitive to the temperature and highly nonlinear, with a distinct thermal threshold at ∼20 °C. In cooler forests, abundant short-range ordered (SRO) iron minerals enhance enzyme activity via complexation, facilitating lignin degradation and the accumulation of iron-bound carbon. In contrast, warmer climates with diminished SRO content exhibit reduced enzyme sorption and SOC stabilization, likely driven by insufficient bioavailable carbon. Synchrotron-based microinfrared analyses (n = 2783 spectra) reveal over a 30% decline in the mineral retention of organic residues under warming, attributed to a weakened mineral–organic affinity. Notably, microbial necromass demonstrated a greater affinity for SRO minerals than plant residues. These findings highlight a temperature-sensitive mineral–enzyme feedback mechanism, which may help predict SOC stability and terrestrial carbon climate feedbacks in a warming world.