Land Use Change Decouples Soil Elements in Agricultural Fields, Northeast China

ABSTRACT Land‐use change, especially conversion to cropland, disrupts elemental coupling and destabilizes soil organic carbon. Using paired soil samples from forest soil, grassland soil, and agricultural soil in Northeast China, we examined how cultivation redistributes mineral‐associated organic carbon and particulate organic carbon and alters multielement interactions. This conversion depleted both mineral‐associated organic carbon and particulate organic carbon, enriched elements including Ca, Cu, Cr Co, Li, Na, Ni, and Pb, and enhanced Mn accumulation through redox cycling. Network analysis revealed that cultivation weakened elemental coupling and decreased the multielement coupling index, despite an increase in network connectivity. Notably, keystone associations in natural soils (e.g., Cu–Zn, Fe–Zn) were supplanted by Mn‐dominated pairs (e.g., Mn–Fe, Mn–Co), signaling a shift from organo–mineral stabilization to redox‐driven processes. These changes impair soil organic carbon storage, disrupt biogeochemical cycling, and diminish soil resilience and nutrient sustainability, thereby threatening long‐term stability of the terrestrial carbon pool.