Integrated Management Facilitates Soil Carbon Storage in Non-Timber Product Plantations in the Three Gorges Reservoir Area

The Three Gorges Reservoir Area (TGRA) in China has extensive non-timber product plantations (NTPP), in which integrated management based on intensive fertilization and weeding were required to maintain and improve yields for a long time. Uncertainties still existed regarding the compound effects of environment and the long-term integrated management on soil organic carbon content (SOC) in NTPP. Data from 341 sampling plots covering six primary NTPP types were collected to investigate the influence of environment and management on topsoil (0–10 cm) SOC of NTPP using a coupled algorithm based on machine learning and structural equation modeling. Results showed significant differences and spatial variabilities in SOC content among different types of NTPP. Integrated management accounted for approximately 53% of the accumulation of topsoil organic carbon, surpassing the total contribution of topography, climate, vegetation, and soil properties in NTPP of TGRA. SOC content increased with available nitrogen for NTPP at all altitudes in TGRA. The study highlighted the potential of enhancing SOC storage through adaptive integrated management in NTPP of vast areas. Improving soil organic carbon stock in large area of non-timber production plantations would benefit the realization of carbon neutralization in next decades.