Ecological security assessment and ecological pattern optimization for Lhasa city (Tibet) based on the minimum cumulative resistance model

The alpine regions of Tibet are biogeographically unique and highly biodiverse. As the political, economic, and cultural center of Tibet, the city of Lhasa's population growth and economic development have further weakened the region's already fragile ecological environment. Coordinating relationships between stable economic development, sustained population growth, rational resource use, and environmental protection has become an urgent issue. This paper establishes an ecological resistance surface based on the ecological resistance factor index to evaluate Lhasa's ecological security level. The obtained results show that the city's ecological security level is good, with high security level in the north, northwest, and northeast, and low-level in the south and the middle of city. High-level ecological security areas accounted for 34.5% of the city's total area, and low-level areas accounted for 9.0%. The overall Moran's I index of the city's ecological security was 0.518. According to a LISA clustering chart, Lhasa's ecological security grades are mainly high-high (HH) and low-low (LL). These two grades showed an apparent flaky spatial clustering in the city. We elected eight large-scale nature reserves in the city as ecological sources, constructed a resistance surface of the ecological accumulation of ecological sources, used the MCR (minimum cumulative resistance) model and gravity model to extract potential ecological corridors, and finally identified potentially important ecological corridors. A total of 51 ecological nodes and 80 potential ecological corridors were extracted, with a total length of about 3449.7 km. The length of the primary and secondary corridors accounted for 32.32% of the total length. Combining the development of Lhasa's ecological economy with tourism and cultural industry planning, a layout of ecological network model with one ring and three belts is proposed. An ecological space development strategy of agglomeration within the ring and axial drive should be implemented. This study provides a decision-making reference for the spatial layout of the ecological industry in Lhasa.