Urban expansion in China and its spatial-temporal differences over the past four decades

The urban expansion process in China from the 1970s to 2013 was retrieved based on remote sensing and GIS technology. With the latest zoning method used as reference, annual expansion area per city, urban expansion type, and fractal dimension index were employed to analyze the Chinese urban expansion characteristics and its spatial difference from the aspects of urban expansion process, influence of urban expansion on land use, and urban spatial morphological evolutions. Results indicate that 1) under the powerful guidance of policies, urban expansion in China went through six different stages, and cities in the eastern region entered the rapid expansion period the earliest, followed by cities in the central, northeastern and western regions; 2) cultivated lands and rural settlements and industrial traffic lands were the important land sources for urban expansion in China; the influence of urban expansion on land use in the eastern region was the strongest, followed by the central, northeastern and western regions; 3) urban spatial morphology tended to be complex and was directly related to the adopted spatial expansion mode. Infilling expansion became the main urban expansion mode in the western region first, then in the central and northeastern regions, and finally in the eastern region. This study establishes the foundation for an in-depth recognition of urban expansion in China and optimization of future urban planning.