Integrating 2-D built-up and 3-D technomass reveals the continuity and hybridity of urban-rural gradient

Abstract

An urban-rural gradient is an effective tool for analyzing urbanization patterns and their impacts on social-ecological systems. However, the prevailing single indicators rarely combine vertical (3-D) spatial structures to depict complex urbanization patterns along the urban-rural gradient from multiple scales. We developed an approach that integrates a two-step clustering analysis based on a grid-township spatial hierarchy. We first integrated built-up (2-D) and technomass (3-D) clustering at the grid scale, which was further aggregated into the township scale. We then quantified and compared the urbanization pattern and its spatial distribution along the urban-rural gradient in Beijing, as an example. We found that at the grid scale, adding the vertical information, technomass, can substantially improve the mapping of spatial heterogeneity of urbanization in urban core areas compared with using 2-D built-up information alone. At the township scale, the aggregation clearly shows three urbanization patterns: urbanity, rurality, and hybrid, and their four types of spatial distribution. Considering the traditionally used landscape indicators such as percent cover of forest, and arable land helped identify the hybrid urbanization patterns in suburbs. Therefore, urbanization along the urban-rural gradient can be characterized as continuous and hybrid. Such findings can enhance our understanding on the spatial pattern of urbanization along an urban-rural gradient, and provide insights for urban planning and resource management insights.