Distribution patterns of SOC fractions and mineralization on sloping erosion-prone farmland in the black soil region

Soil organic carbon (SOC), primarily accumulated in the surface layers of sloping farmland, experiences disrupted distribution due to soil erosion, affecting its lateral transport and vertical sequestration. To gain a deeper understanding of the interaction between soil erosion and the carbon cycle, this study assessed the effects of two tillage practices, as slope-ridge tillage (SRT) and cross-ridge tillage (CRT), in controlling soil erosion on long gentle sloping farmland in the Northeast black soil region in China, while evaluating spatial variations in erosion rates, SOC content, and SOC fractions using the Caesium-137 ( 137 Cs) technique combined with wavelet analysis. The findings revealed lower 137 Cs inventories for both SRT (732.96 Bq·m −2 ) and CRT (1000.98 Bq·m −2 ) compared to the reference value (2468.77 Bq·m −2 ), confirming the occurrence of soil erosion. CRT showed a significantly lower erosion rate (3056.65 t km 2 ·a −1 ) than SRT (4409.04 t km 2 ·a −1 ), indicating greater effectiveness in erosion control. Wavelet analysis further uncovered periodic erosion-deposition patterns under both tillage practices, which corresponded to variations in SOC content and its fractions. A significant negative correlation was observed between SOC content and cumulative mineralization, with soil erosion rate emerging as a critical driver of these relationships. Correlation analysis confirmed that SOC fractions play a crucial role in driving SOC mineralization and are intricately linked with SOC dynamics. Random forest analysis identified soil erosion rate, SOC, and dissolved organic carbon (DOC) content as key factors influencing SOC mineralization under SRT. The findings suggest that CRT is more effective in reducing soil erosion by modifying microtopography, thereby minimizing the migration of mineral-associated organic carbon (MAOC) and enhancing SOC retention. This research provides critical insights for developing sustainable land management practices in the region, mitigating the adverse impacts of erosion on the carbon cycle.