Effects of Land Reclamation on the Stability of Soil Organic Carbon Pool in Floodplains

ABSTRACT Land reclamation significantly alters floodplain structure and function, affecting soil organic carbon (SOC) dynamics, which are crucial for soil fertility and carbon sequestration. However, few studies have examined SOC variation following floodplain reclamation. This study investigated the effects of land reclamation on SOC pool and stability in the floodplain along the lower Yellow River, utilizing soil samples from four land types (exposed beaches [EB], farmlands [FL], planted forests [PF], and wetlands [WL]) across three seasons (spring, summer, and autumn). Reclamation significantly increased SOC, labile organic carbon (LOC), non‐labile organic carbon (NOC), and the carbon management index (CMI) in topsoil (0–20 cm) compared to EB ( p < 0.05). However, SOC, LOC, NOC, and CMI were significantly reduced in deeper layers (below 20 cm), particularly in FL and PF. Seasonal variations in LOC and CMI were also affected by reclamation, especially in FL. While reclamation did not alter SOC stability over time, it enhanced stability in deeper SOC pools and reduced seasonal fluctuations in the stability of the SOC pool, particularly in FL. Correlation analysis, random forest modeling, and partial least squares structural equation modeling (PLS‐SEM) indicated that soil water content mediated the impact of reclamation on the stability of the SOC pool, while soil enzyme activity, nitrogen composition, and LOC determined seasonal changes. These results provide detailed information for the management measures in floodplain ecosystems.