Analysis of the Evolution and Driving Mechanisms of Terrain Niches of Rural Settlements in the Mountain–Plain Transition Zone of Hebei Province

In mountain–plain transition zones, steep environmental gradients impose real limits on the persistence of rural settlements. They determine not only where settlements can locate, but how they function daily. Taking Hebei Province as a case, we built a “terrain niche” framework to trace how these settlements have shifted over space and time and to uncover the factors driving those shifts. Using land-use and geospatial data for 2005, 2010, 2015 and 2020, this study built a three-part analysis: niche characterization, occupation, and adaptation. Furthermore, the terrain position index, distribution index, landscape metrics, kernel density estimation and the Geodetector model were applied. Results show a clear and growing preference for low terrain. Over 71% of new settlement area clustered in the most favorable niche and its distribution index rose from 1.54 to 1.68. Landscape patterns changed along the gradient: plains became more aggregated and regular, but mountainous areas grew more fragmented and complex. Then a “core polarization–peripheral decline” spatial pattern, with plains settlements expanding and mountain settlements retreating, was found. Slope and rural population were the dominant driving factors overall, but interactions among factors were stronger. Combinations like slope ∩ rural population and road network density ∩ Xiong’an policy showed strong nonlinear enhancement.