Spatiotemporal dynamics of urban expansion in 13 cities across the Jing-Jin-Ji Urban Agglomeration from 1978 to 2015

摘要

The newly implemented national policy "To build a world-class agglomeration of cities with the capital as the core" made the Jing-Jin-Ji Urban Agglomeration attract attention from both the scientific community and society. Here we quantified and compared the magnitude, rates, forms, and dynamics of urban expansion for 13 cities across the Jing-Jin-Ji Urban Agglomeration, and examined the relationship of urban patch structure and hierarchical structure of urban growth over the past four decades. We found that the rates and composition of urban expansion forms (i.e., infilling, edge-expansion and leapfrogging) varied considerably across cities and over time, due to national and regional policies, physical features and the urban administrative hierarchy. The overall annual urban expansion rate for the 13 cities was 5.5 +/- 2.0% (mean standard deviation) between 1978 and 2015. Leapfrogging was the dominant urban expansion form in early period, edge-expansion took the leading role since 1990, and the contribution of infilling was generally less than 40%. Our results revealed that although three major cities (i.e., Tianjin, Beijing and Shijiazhuang) of the Jing-Jin-Ji Urban Agglomeration contributed 36.6% of the urban land area increase of this region, larger cities might not be better positioned for urban expansion. The urban expansion rates of cities were inversely related to city size in general from 1978 to 2015 with exception only from 2005 to 2010. Patch analysis showed that relationship between patch number and patch size derived previously at the national level can be applied to the Jing-Jin-Ji Urban Agglomeration despite the discrepancies in temporal scale and urban administrative hierarchy. This invariant self-organization of urban land patches during the urbanization process might provide insightful information guiding the design, planning, and management of sustainable cities in the capital urban agglomeration of China.