Eco-zoning management based on thresholds of NPP driving factors

The spatiotemporal differentiation of net primary productivity (NPP) is non-linearly regulated by multiple factors, with the identification of driving factor thresholds and ecological zoning remaining a key challenge in ecosystem research. This study examined the spatiotemporal evolution of NPP using the Sen+MK test and the Hurst index. It then identified thresholds and interactions among NPP driving factors through an XGBoost–SHAP–Restricted Cubic Splines (RCS) model. Finally, it developed ecological zoning based on the identified thresholds. The main conclusions are as follows: (1) Over the past 21 years, NPP in the study area exhibited a fluctuating upward trend with significant spatial heterogeneity (higher in the west, lower in the east), and a potential decline is projected for the future. (2) Driving factors were ranked by importance, and their critical thresholds identified: precipitation (1103.77 mm) > soil organic matter content (4%, 8.31%) > vegetation index (0.44) > elevation (129.99 m) > temperature (13.71 °C) > distance to roads (1.11 km) > distance to water bodies (1.65 km, 8.91 km) > slope (7.24°) > distance to residential areas (4.1 km) > nighttime light intensity (1.55 NW/cm 2 /sr). Significant non-linear effects and interactions among the driving factors were identified. (3) Ecological zoning was implemented based on the identified critical thresholds. The results indicate that most areas of Yichang City were classified as key protection zones and key prevention zones, primarily influenced by natural factors; while a small portion was designated as key treatment zones, primarily influenced by anthropogenic factors. This zoning provides a clear scientific basis for implementing differentiated ecosystem management strategies.