Accelerated urbanization and population growth have resulted in the loss of ecological land and biodiversity, accompanied by the degradation of ecosystem services. Identifying and improving existing ecological security patterns are of great significance for maintaining the sustainable development of cities. In this study, Jinan, the capital of China's Shandong Province, was used as a case study area. Based on three ecosystem services, namely, soil conservation, water conservation and carbon fixation, ecological sources were determined. Furthermore, a resistance surface was constructed based on biodiversity. On these bases, the circuit theory concept of random walks was applied to simulate ecosystem processes in a heterogeneous landscape and identify ecological corridors, pinch points and barriers. A total of 25 ecological sources, 48 ecological corridors and 19 pinch points were identified, and restoration areas were delimited to three levels. These elements together constituted the ecological security patterns. Specifically, the ecological sources were mainly distributed in southern Jinan and were covered mostly with forest land. The ecological corridors were located mainly in the eastern and southwestern plains below the southern mountainous areas and were covered mostly with cropland. Furthermore, the eastern corridors were much longer than the southwestern corridors. Pinch points were distributed mostly along rivers or around large-scale construction land. Barriers were distributed mainly in Zhangqiu District and northern Licheng District. Based on these findings, hierarchical restoration areas were delimited. Differentiated development contradictions in restoration areas were discussed, and corresponding ecological protection measures were proposed. An ecological security optimization pattern of "one center, two wings, and two belts" was finally proposed to provide planning strategies for decision-makers.
Keywords: Circuit theory; Ecological restoration areas; Ecological security; Ecological security patterns; Ecological services; Jinan, China.