Terrain-mediated vegetation dynamics and their drivers in the Qihe River Basin: A gradient-based assessment of recovery and future persistence

In small and medium-sized basins, vegetation dynamics critically influence watershed sustainability through their effects on water retention, soil stability, and biodiversity but face unique challenges from complex terrain and human–nature interactions. This study investigates how natural and anthropogenic factors interact with the terrain to drive spatiotemporal vegetation changes in the Qihe River Basin. Using Sen's slope estimator and the Mann–Kendall test, we analyzed the long-term trend of the NDVI in the Qihe River Basin across different topographic gradients. The NDVI of vegetation on the second tier increased at a rate of 0.0088, which was higher than the third-tier NDVI rate of 0.0067. The spatial distribution and changes in the NDVI were examined with ArcGIS. The major driving factors of the NDVI were quantitatively assessed using a geographical detector model. After 2004, the explanatory power q values of land use factors in the Qihe River Basin ranked first at 0.334, 0.503, and 0.399, which were higher than those of natural factors such as potential evapotranspiration, temperature, precipitation, and elevation, providing insights for future watershed management. Finally, the spatial trend of the NDVI in the Qihe River Basin was projected on the basis of the Hurst exponent (H). The average H value of 96% of the Qihe River Basin was 0.36, indicating that the NDVI in the Qihe River Basin will show a weak persistent development trend in the future. The main findings from the analysis of the NDVI variations across the gradients in the Qihe River Basin are summarized as follows: (1) significant regional disparities existed in vegetation coverage, with western high-elevation regions exhibiting notably higher coverage than eastern lowlands did; (2) after 2004, overall vegetation coverage increased, reflecting the efficacy of ecological restoration initiatives; and (3) the driving factors of vegetation change exhibited terrain-dependent variability, with terrain, land use, and slope being primary in mountainous regions, while potential evapotranspiration and elevation dominated in plain areas. Natural factors, particularly evapotranspiration, temperature, and precipitation, are the primary drivers, with 80% of vegetation showing positive trends, indicating robust ecosystem health. This study provides valuable insights for adaptive terrain management and ecological restoration.