Construction and optimization of ecological networks in karst regions based on multi-scale nesting: A case study in Guangxi Hechi, China

Under the background of rapid urban expansion, constructing ecological networks (ENs) is an effective way to alleviate the contradiction between ecological protection and economic development and to ensure regional ecological security. However, most existing EN models are constructed from a single-scale perspective and lack nested integration between multiple scales. Therefore, taking Hechi, a typical karst mountainous city in southwest China, as the study area, the least-cost path and circuit theory were used to construct and superimpose the EN at two scales, Hechi municipal and main urban area, identify ecological sources, corridors, pinch points and barriers that affect nested integration of scales, and propose specific optimization strategies for the EN structure. The results show that the overlapping ecological sources at the two scales cover an area of 485.38 km2 and the corridors overlap in length by 45.77 km, and that the overlapping regions are crucial to the stability of the multi-scale EN articulation and need to be protected in a focused manner. Identify 25 and 10 pinch points between the municipal and main urban area, overlapping 6; 18 and 7 barriers, overlapping 4; the overlapping ecological pinch points and barriers are areas with a high possibility of species migration and strong obstruction of movement, which should be protected and repaired as a priority. In addition, this study proposes specific management measures for the EN in Hechi from a ‘polygon-line-point’ perspective. In conclusion, this study makes up for the shortcomings of constructing ENs in karst areas at a single scale. Our research can also provide a reference for decision-making on ecological security protection, integrated land management and ecological restoration in karst mountainous regions.