Topographic gradient differentiation of land use in mountainous cities: a multi-temporal analysis of Nan’an District, Chongqing

Revealing the topographic gradient differentiation of land use in mountainous cities is essential for optimizing land-use allocation in complex terrain regions. Taking a typical mountainous urban area Nan’an District of Chongqing as a case study, this paper examines the topographic gradient characteristics and evolutionary patterns of its land-use structure using a Topographic Position Index and a topographic distribution index(DI), based on multi-temporal Sentinel-2 imagery and DEM data. The results indicate that: (1)Land use in Nan’an District is dominated by construction land and forest land; construction land is concentrated in low topographic gradient areas, whereas forest land predominates in medium and high gradient zones. (2)Topographic gradient differentiation of land use has progressively intensified: in low-gradient areas, construction land has expanded while cultivated land has shrunk, and in medium- and high-gradient areas, forest land has maintained a stable dominance. (3)The distribution advantages and structural characteristics of land use exhibit marked spatio-temporal variation across different topographic gradient levels. (4)The correlation between topography and land-use distribution is significant and persistent,which confirms that topography is a core constraining factor shaping and driving land-use patterns and their evolution in mountainous cities.