Hierarchical structure analysis of urban carbon metabolism: A case study of Beijing, China.

• The hierarchical structure could give information to a low-carbon city. • Energy-related carbon emission of economic activities dominated the system. • Integrated flows indicated the importance of primary consumers and producers. • Beijing's spatial gradients transformed from single-center to multi-center. • Beijing's ecological hierarchy indicated a better organized metabolic structure. An integral analysis of urban carbon metabolism can support efforts to build a more sustainable city: the spatial gradients provide insights into how to guide future land use and cover change, while ecological network hierarchy provide insights into the self-mutualistic interactions of the city's carbon metabolic structure. In this study, we combined a spatially explicit network with carbon budget of energy consumption and land use and cover change in Beijing, China. From 1990 to 2010, energy related carbon emissions accounted for roughly 90% of the city's total. The network's integrated flux decreased at an average rate of 7.5%. The output flux primarily decreased when moving outward from the center through the periphery of southeastern plains and towards the northwestern mountains. In contrast, the input flux increased moving from the periphery to both the center and mountains. The ecological hierarchy was irregular based on both the driving and pull weights for the components of the model, with excessively small producer and decomposer layers and excessively large consumer layers. The changing structure of Beijing's carbon metabolism over time indicated a tendency to a better organized city. Understanding the evolution of these hierarchies during urban development provides a more solid empirical basis for improving use of the urban space and reducing carbon emission. [ABSTRACT FROM AUTHOR]