Research on the synergy of urban system operation-Based on the perspective of urban metabolism.

Cities have been posing threats to local environment due to intensive human activities. Disordered urban metabolism can lead to unhealthy urban system operation. Studying urban metabolism can identify the characteristics and structure of urban system operations, thereby promoting sustainable development. We construct an ecological network to model the energy/material flows among the sectors of urban system in Beijing, Shanghai, Tianjin, and Chongqing, which are the most representative cities of China. Ecological network analysis was introduced to survey the system's characteristic of structure and function. Results show that Shanghai's urban metabolic system has the highest synergism with a value of 5.04, followed by Beijing, Chongqing, and Tianjin. Different cities vary considerably in terms of the relationships among the sectors. In Beijing and Chongqing, there is mutualistic relationship between environment and primary industry. Transportation forms a mutualistic relationship with tertiary industry and other sectors Only in Chongqing. The good relationships between primary industry and construction are merely seen in Beijing and Shanghai. However, some relationships are similar in the four cities, for instance, all the relationships between primary industry and advanced industry, and between construction and advanced industry are competition; All the relationships between environment and transportation are mutualism. We further explored the network stability and found that the studied urban systems are all located in a stable status relatively. Our research could reveal the synergy of urban operation, and provide a theoretical basis for optimizing urban metabolic processes by regulating the flows and guidance for sustainable urban development.