Spatial pattern of urban change in two Chinese megaregions: Contrasting responses to national policy and economic mode.

Spatial pattern of urban change reflects the urbanization process. Previously, studies on the change of city more focused on the large cities and neglected the urban megaregion growth processes that may include changes in smaller cities. In this study, we investigated the spatial pattern of urban change in the megaregion development process. In addition, we discussed the megaregion responses to the national policy and economic growth mode. We chose the Beijing-Tianjin-Hebei (BTH) and Yangtze River Delta (YRD) urban megaregions as our study areas and comparatively quantified the urban expansion and change based on developed land at both the regional and city scales during 1984-2010. We found: 1) both the BTH and YRD experienced rapid urbanization, the magnitudes, rates, and spatial patterns of urban expansion, however, were very different between the two megaregions. In BTH, the magnitudes and rates of urban expansion were greater in larger cities than in medium- and small-sized cities through the entire period of 1984-2010. In contrast, the magnitudes and rates of urban expansion in YRD were greater in some medium- and small-sized cities than in larger cities from 1984 to 2000, and became similar from 2000 to 2010. 2) The BTH consistently followed a double-nucleated expansion pattern, while the spatial pattern of the YRD changed from single nucleated pattern to multi- nucleated pattern. A further analysis showed that while national policies on urbanization have to some extent guided the urbanization development in the two megaregions, economic growth modes seemed to play a more important role in affecting the urban growth patterns.