[Vegetation cover changes and their responses to natural and anthropogenic factors in the Luanhe River Basin]

Dynamically assessing vegetation cover changes and their responses to ecological factors in the Luanhe River Basin is crucial for ensuring regional ecological security and promoting the sustainable development of the Beijing-Tianjin-Hebei urban agglomeration. In this study, the Luanhe River Basin was divided into two ecological zones (Inner Mongolia Plateau Ecoregion and North China Mountain Ecoregion). Using Theil-Sen median trend analysis, the Mann-Kendall test, and the optimal parameters-based geographical detector model, we systematically analyzed the spatiotemporal characteristics of vegetation change from 2000 to 2019 and quantified the effects of natural and anthropogenic factors. The results showed that the normalized difference vegetation index (NDVI) exhibited an overall increasing trend with fluctuations from 2000 to 2019, with a mean value of 0.72 and a growth rate of 0.0051·a^-1. The NDVI growth rate in the upstream plateau ecological zone was higher but less stable, whereas vegetation in the midstream and downstream mountain ecological zone exhibited greater stability. Annual precipitation, annual sunshine duration, and land-use type conversion were identified as key drivers of NDVI variation, with explanatory power (q-values) of 0.22, 0.18, and 0.17, respectively. Among them, the interaction between annual precipitation and soil type was the most significant (q=0.32). Land use changes significantly contri-buted to vegetation improvement, with an average NDVI increase of 0.16 in ecological restoration project areas. By revealing the synergistic mechanism of natural and anthropogenic factors on vegetation cover changes, our results provide scientific support for ecological conservation and land management policies in the Luanhe River Basin.