Diagnosing urban ecological vulnerability in multi-mountainous city from a 3D landscape perspective

In fragile karst mountain cities, the conflict between intense development activities and ecosystem integrity poses significant challenges to sustainable design. Although urban expansion is often studied through two-dimensional landscape patterns, the critical role of three-dimensional spatial structures remains poorly understood, limiting effective ecological engineering interventions. This study focuses on Guiyang's built-up area from 2010 to 2023, establishing a foundation for ecosystem restoration planning by diagnosing ecological vulnerability mechanisms. By integrating the PSR model with spatial analysis techniques (geodetector, bivariate spatial autocorrelation analysis, and GTWR), we quantified the spatiotemporal dynamics of ecological vulnerability and elucidated the influence mechanisms of both two-dimensional and three-dimensional landscape patterns. The findings provide actionable insights for ecological engineering practice: (1) From 2010 to 2023, Guiyang's built-up area exhibited a distinct landscape pattern characterized by intensive, orderly development in the core zone and fragmented expansion in peripheral areas. Overall ecological vulnerability intensified, manifesting as a spatiotemporal pattern of expansion from the center to the periphery. (2) Three-dimensional building indicators—BN, BCR, FAR, and BRI—exhibit stronger explanatory power for ecological vulnerability, indicating that vertical urban expansion is the dominant driver of ecological fragility; (3) Natural topography exhibits a double-edged sword effect: contiguous vegetation in complex terrain can serve as natural buffers, while specific topographies in southern and peripheral areas require targeted engineering measures to prevent exacerbating anthropogenic pressures. (4) While two-dimensional landscape patterns are not direct pressure sources, high concentrations of developed land significantly amplify vulnerability. Landscape composition uniformity shows a significant negative correlation with ecological vulnerability, with high-vulnerability zones consistently occurring in overlapping areas of high building density and spatial concentration. The mechanism revealed in this study—“three-dimensional building drivers—two-dimensional pattern regulation—natural topography constraints”—provides a scientific framework for future ecological engineering practices. This framework aims to mitigate ecological vulnerability in karst mountain cities and promote sustainable ecosystem design.