Extracellular catalysis is a key rate-limiting step in soil organic matter decomposition, which underpins soil carbon-climate feedbacks. Conventionally, extracellular catalysis is primarily attributed to biotic enzymes. However, the contribution of abiotic processes to extracellular catalysis remains largely unquantified in terrestrial ecosystems, leading to inaccuracy in our understanding of soil carbon degradation potentials and responses to global changes. Here using a large-scale investigation across diverse ecosystems, assisted with validation experiments and laboratory simulations with commonly occurring soil minerals, we demonstrate that abiotic catalysis, primarily driven by iron- and manganese-containing minerals, contributes on average 43% (7-99%) and 54% (15-92%) of total oxidative and hydrolytic activities in soils, respectively. Moreover, unlike enzyme-driven catalysis that varies with environmental changes, abiotic catalysis maintains a constant activity under varying temperature, pH, microbial activity, and moisture conditions. Based on the large-scale soil survey results, we further reveal that abiotic catalysis plays particularly important roles in biologically unfavorable environments such as deep soils and wetlands where reactive minerals accumulate. Overall, our findings refine the current enzyme-centric paradigm and reveal the previously underappreciated role of abiotic catalysis in regulating soil carbon decomposition and climate feedbacks across terrestrial ecosystems.
Zhao et al. (Sat,) studied this question.