Comparing the Spatiotemporal Dynamics of Urbanization in Moderately Developed Chinese Cities over the Past Three Decades: Case of Nanjing and Xi’an

Urbanization has substantially altered the landscape throughout the world, and most previous studies have concentrated in areas with fast urbanization. Urbanization with moderate rates has received relatively less attention. Here, the urban patterns and dynamics in two moderately developed Chinese cities (i.e., Nanjing and Xi’an) are analyzed and compared using multitemporal Landsat Multispectral Scanner (MSS), Thematic Mapper (TM), and Enhanced Thematic Mapper Plus ($\mathrm{ETM}+$) images of circa 1980, 1985, 1990, 1995, 2000, 2005, and 2010 integrated with landscape metrics and urban growth type analysis. Results showed that both cities experienced a rapid expansion of urban land from 1980 to 2010, with a 7.2 and 8.5 times increase for Nanjing and Xi’an, respectively. The urbanization process of both cities can be divided into two stages (the diffusion phase and the transition period from diffusion to coalescence) that were roughly consistent with the phase oscillation theory of urban development. The first phase was during 1980–1995 for Nanjing and 1980–1990 for Xi’an, characterized by scattered development of new urban areas, an increase of the number of patches (NP), a decrease of mean patch size (MPS) and mean Euclidean nearest-neighbor distance (ENN_MN) for urban land, and high proportion of outlying urban growth type, resulting in increasing landscape fragmentation. The second phase was from 1995 to 2010 for Nanjing and from 1990 to 2010 for Xi’an when the newly developed urban areas became aggregated and compact, NP increased slowly, MPS increased, ENN_MN generally remained stable, and edge-expansion became the dominant urban growth type. The detailed quantitative analysis on the general trends of urbanization and urban growth patterns in Nanjing and Xi’an provide insights for future efforts on a comprehensive understanding of urbanization in China.