Comparison of landscape patterns between metropolises and small-sized cities: a gradient analysis with changing grain size in Shanghai and Zhangjiagang, China

Quantifying the urban landscape pattern and its change is fundamental for monitoring and assessing the ecological and socio-economic consequences of urbanization. Using Indian Remote Sensing Panchromatic (IRS-PAN) imagery of 2002 and combining gradient analysis with landscape metrics, we compared the landscape patterns between metropolises and small-sized cities with increasing grain size. Landscape metrics were computed along a 51 x 9 km transect cutting across Shanghai and a 16 x 2 km transect cutting across Zhangjiagang with a moving window. The results showed that fragmentation indices (patch density (PD), total edge (TE), landscape division (LD)) in land use transects of the two cities had many similarities, indicating the common characteristics of urbanization in different-sized cities. There were, however, some striking dissimilarities between the two cities, which did not support the hypothesis that PD increases exponentially along a landscape modification gradient. These differences may have three explanations: the proportion of urban roads area, the width of urban roads and land use change in suburban and rural areas. The proportion of urban road area and the width of urban roads, which should be considered in future research, are two main factors that have been identified to influence the landscape pattern analysis. In younger and smaller cities, spatial competition between local interest groups and imperfect land managerial systems result in an increase in fragmentation in the suburbs, and policymakers should pay more attention to future city planning and management. A bridge linking the urbanization landscape pattern and the process of urban fragmentation will be a key to urban landscape studies and planning.