Earthworms drive type-dependent mitigation of microplastic-induced SOC mineralization potential in semi-arid agroecosystems: microcosm evidence

Microplastic (MP) pollution potentially enhances soil organic carbon (SOC) mineralization, while earthworms function as critical regulators facilitating SOC sequestration in agroecosystems. However, the mechanistic pathways by which earthworms mediate MP-induced stimulation of SOC mineralization remain poorly elucidated. Here, a 120-day full-factorial microcosm experiment was established to disentangle the effects of MPs (no MPs vs. biodegradable MPs vs. non-biodegradable MPs) and earthworms (presence vs. absence) on SOC mineralization potential in semi-arid agroecosystems of the Loess Plateau. We found that both MP types significantly enhanced SOC mineralization potential by over 30%, whereas earthworms suppressed it by ∼35%. Regardless of MP types, earthworms counteracted over 40% of MP-induced SOC mineralization potential. Notably, the magnitude and underlying pathways of earthworm-mediated mitigation strongly depended on MP types. When exposed to biodegradable MPs, earthworms suppressed the activities of extracellular enzymes ( e.g. , β-glucosidase and N -acetyl-β-glucosaminidase) via alleviating soil nutrient limitations. Under non-biodegradable MPs, earthworms stabilized SOC stocks by promoting soil aggregation. Collectively, these findings reveal a novel type-dependent mechanism whereby earthworms buffer microplastic-induced soil carbon destabilization in semi-arid agroecosystems. This work advances our mechanistic insights into soil fauna-mediated carbon cycling and provides promising nature-based strategies for stabilizing SOC sequestration amid ongoing global change.