Spatiotemporal variation of vegetation cover and habitat quality in the central loess hilly region of Gansu Province: A case study of Dingxi City

The central loess hilly region of Gansu Province—a typical ecologically fragile zone—is located in the central part of the Loess Plateau. The terrain is fragmented, soil erosion is severe, and vegetation restoration has always been a major challenge for ecological protection. This study focuses on the spatiotemporal evolution of vegetation and the ecological environment, considering Dingxi City in Gansu Province as a case study. Based on land use and normalized difference vegetation index (NDVI) data from 2000 to 2020, Sen+Mann-Kendall trend analysis and the InVEST model were employed to investigate the dynamic evolution of vegetation cover and the ecological environment in the area. The results indicate that the annual maximum NDVI values of Dingxi City exhibit a spatial distribution pattern of “high in the southwest and low in the northeast,” with a fluctuation increase at a rate of 0.0078 each year. A total of 98.26% of the area showed an improvement trend, among which 89.02% exhibited a marked improvement trend. The mean habitat quality increased from 0.3329 in 2000 to 0.3376 in 2020, but over 91.74% of the area remains in the “poor” category. High-quality areas (NDVI>0.6) are concentrated in the southwestern forest areas, covering approximately 7.81% of the total area, whereas low-quality areas are mainly distributed in the northeastern agricultural and grassland areas with intensive human activities. This study reveals the evolution patterns of NDVI and habitat quality in Dingxi City, providing quantitative evidence for ecological protection, land use planning, and policy formulation in the central loess hilly region of Gansu Province.