Optimization of ecological node layout and stability analysis of ecological network in desert oasis : a typical case study of ecological fragile zone located at Deng Kou County(Inner Mongolia)

Optimization of coverage control strategy for spatial ecological nodes and the correct evaluation of the stability of spatial ecological network structure are the basis for understanding and optimizing the ecological network structure. The excellent ecological network structure, especially in arid and semi-arid regions in northwest China, is the basis of sustainable development of regional ecological environment. Based on this, Deng Kou County, the typical ecological vulnerable zone, was chosen as the study area. Minimum cumulative resistance model improved by emergy theory was used to extract the ecological network, and a new spatial layout strategy based on Tyson blind zone was constructed to optimize the spatial layout of ecological nodes. In the aspect of ecological network stability, the connectivity robustness and recovery robustness index were used to analyze structural robustness of un-optimized and optimized ecological network. The results showed that the spatial distribution of ecological source nodes at level 3, 4, and 5 with higher emergy value formed the desertification protection pattern. 1058 ecological nodes and 47,466 ecological corridors were extracted at the county level, which formed the ecological network in Deng Kou County. After optimization, the coverage area of ecological nodes reached 1870.03 km(2), and the area of Tyson blind spot was reduced to 1179.27 km(2). Compared with the un-optimized ecological nodes, the spatial distribution of the optimized ecological nodes was more homogeneous, the coverage index (CR) of the optimized ecological nodes reached 87.79%, and the distribution uniformity (U) of optimized ecological nodes was reduced to 0.3978. Based on the above, the robustness of the un-optimized and optimized ecological network structure was analyzed. The initial connectivity robustness of the un-optimized ecological network was 0.73, but the optimized ecological network was 1. The optimized network was more stable than the un-optimized network. For these two kinds of networks, the malicious attack was more destructive than the random attack. The node recovery robustness and edge recovery robustness under random attack were superior to those of the malicious attack. In summary, the spatial layout optimization of the ecological nodes improved the stability of the ecological network in Deng Kou County. This analysis provided insights that will support planning to adjust the ecological spatial structure and future sustainable development of ecological environment.