Abstract: Constructing ecological security patterns and optimizing ecological spatial structure are important ways to guarantee regional ecological security and ecosystem stability, with positive significance for alleviating the contradiction between ecological protection and economic development. Taking the eastern part of the sand prevention belt in Northern China as study area, we identified ecological sources through the ecological assessment method of ecological vulnerability and importance of ecological service function, extracted ecological corridors and ecological nodes with the circuit theory, constructed a two-phase ecological security pattern in 2000 and 2015, and put forward the optimization measures. The results showed that: (1) From 2000 to 2015, the area of highly vulnerable areas decreased, whereas that of non-vulnerable areas increased. The overall habitat quality improved, the water conservation significantly increased, and the actual wind erosion intensity weakened. Those results indicate that regional ecological environment tended to improve and the sand control had achieved remarkable results. (2) The areas of ecological sources, ecological corridors, and nodes increased from 3837.3 km², 38, and 4 in 2000 to 11619.5 km², 96, and 28 in 2015, respectively. Such a result indicated that the network system of ecological security pattern in the study area tended to be complex and perfect in the past 15 years, and the ability to guarantee ecological security had been improved. Accordingly, we should increase the number and scope of ecological sources, strengthen the construction and protection of artificial green areas to set buffer zones, avoid cutting off ecological corridors by human activities, and strengthen the protection and optimization of ecological functions of the original nodes, to guarantee the integrity of the ecological corridor network. This study provides a reference for promoting a synergistic and mutually beneficial relationship between regional socio-economy and ecological environment and achieving sustainable development.

Key words: ecological vulnerability, ecological service function, ecological source, ecological corridor, optimization measure.