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• 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]

An integrated analysis of urban carbon metabolism from both input and output perspectives can present new insights to support carbon mitigation. In this study, we combined a previously developed spatially explicit network model with an analysis of carbon sequestration and emission by different land use or cover types, and illustrate its use by examining carbon flows in Beijing, China, from 1990 to 2015. The goals were to characterize the temporal changes of the integrated (total direct + indirect) flow structure by applying ecological network analysis and to identify the structure of the urban metabolism by analyzing temporal and spatial changes of the integrated flows. The results showed that the similarity between input and output trophic structures and their spatial pattern indicate increasingly carbon-balanced urbanization by Beijing. The balanced input and output flows for the transportation and industrial land and cultivated land played key roles in forming a central area of aggregated carbon flows between the city's peripheral plains, which also resulted in similar trophic structures for inputs and outputs. Understanding the evolution of the integrated flows during urban development provides a more solid empirical basis for regulating land-use change, improving land consolidation, and reducing carbon flows. Image 1 [ABSTRACT FROM AUTHOR]