Temporal and Spatial Evolution of Habitat Quality and Its Topographic Gradient Effect in Xinzhou City Based on InVEST Model from 1985 to 2020

The ecological response of habitat quality to land use change and topographical factors has become a prominent subject of research in ecology. In view of the unclear response status of habitat quality in Xinzhou City, Shanxi Province, the InVEST model was used to assess its habitat quality from 1985 to 2020, and the terrain factor was used to study its terrain gradient effect. The results show that the land use change in Xinzhou City during the period of 1985 to 2020 mainly involved the mutual conversion of cultivated land and grassland, as well as the conversion of forest land and cultivated land to construction land. The average habitat quality index in Xinzhou City exhibited a slight decline followed by a significant upward trend, with the lowest being 0.739 1 in 1990 and the highest being 0.787 4 in 2020. The area occupied by higher-quality habitats with the habitat quality index ≥0.8 gradually increased, mainly distributed in mountainous and loess gully areas. The area of lower-quality habitats with the habitat quality index ranges from 0.2 to 0.4 gradually decreased, mainly distributed in basin areas. The low level habitats with the habitat quality index below 0.2 also gradually increased. The change in habitat quality from 1985 to 2020 demonstrated clear spatial differentiation: significant gains in 8 counties in the west, notable losses in Xinfu District and Dingxiang County in the southeast. Meanwhile, there is a significant topographic gradient effect, and the habitat quality in basin areas with low terrain gradients has degraded in certain extent. The improvement in habitat quality is greatest in the loess gully area with medium terrain gradient. The habitat quality is highest in mountainous areas with high terrain gradients. The research results can provide decision-making references for improving regional ecological quality and optimizing ecological land use.