Soil organic matter persistence emerges from recursive microbial necromass and mineral feedbacks

Soil organic matter (SOM) constitutes the largest terrestrial carbon pool, yet its dynamics remain poorly predicted by current Earth system models that partition SOM into mineral- and aggregate-mediated pathways based on litter chemistry, largely overlooking microbial contributions to long-term persistence. We show that while fine litter contributes to both pathways, SOM persistence emerges from a recursive microbial necromass–mineral cycle. Litter-derived microbial necromass initiates organo-mineral aggregation, shifting microbial metabolism from substrate-selective bacterial assimilation to fungal-mediated, non-selective SOM catabolism. This reprogramming sustains the cycle, generating recursive microbial–structural–stoichiometric feedbacks that progressively convert particulate organic matter into a stable yet dynamically recycling mineral-associated pool. When disrupted—often due to stoichiometric imbalance—these feedbacks intensify microbial competition and accelerate carbon loss, particularly in long-cultivated soils with degraded resilience. Our framework establishes iterative microbial life–death cycles within plant-derived microsites as the central engine of SOM dynamics, resolving long-standing SOM paradoxes and providing a mechanistic, process-explicit foundation for understanding the soil–microbe ecosystem as self-organizing, thereby improving carbon–climate projections and guiding resilience-focused soil stewardship.