Rice Cultivation Duration Drives Soil Organic Carbon Stabilization in Saline-Alkaline Paddy Soils via Mineral-Associated Organic Carbon Accumulation and Biological Pathways.

Continuous paddy reclamation is a promising strategy for restoring sodic lands, yet the exact mechanisms driving soil organic carbon (SOC) stabilization remain insufficiently quantified. Here, we investigated SOC dynamics across a 12-year rice cultivation chronosequence (0, 2, 5, 10, and 12 years) at 0-20 cm and 20-40 cm depths in western Jilin Province, China. Successive rice cultivation progressively alleviated saline-alkaline stress, with electrical conductivity (EC) decreasing by 70.11% in topsoil after 12 years, establishing a stabilized soil environment by years 10-12. Concurrently, topsoil SOC and total nitrogen (TN) increased by 63.09% and 26.02%, respectively. This physicochemical amelioration triggered a directional carbon transformation: while particulate organic carbon (POC) accumulated in early stages, mineral-associated organic carbon (MAOC) dominated medium-term storage, expanding by 147.12% in topsoil and elevating its share of SOC. Fourier transform infrared (FTIR) spectroscopy confirmed a shift toward molecular structural persistence, marked by increased aromaticity and hydrophobicity. Partial least squares path modeling (PLS-PM) demonstrated that cultivation duration directly drove soil stability (β = 0.94, p < 0.001), operating through a hierarchical cascade where management-induced stress reduction enhanced soil enzyme activity and microbial processing, thereby accelerating the conversion of labile plant inputs into mineral-protected MAOC. Overall, this study quantifies the pivotal role of paddy management in driving organo-mineral protection and chemical persistence, providing a mechanistic framework for carbon sequestration in degraded agroecosystems.