Ecological Indicators (Jan 2025)
Evolution paths of urban forms influenced by landforms: Asynchrony but convergence
Abstract
Current dynamic indices often overlook the global physical gravitation and the interactions between new and old urban patches, leading to errors in assessing their agglomeration effects. Furthermore, the heterogeneity of urban patches, exacerbated by complex terrain, contributes to these inaccuracies. So we introduce the mean location centrality index and the mean location centrality aggregation index to address these issues. This study focuses on county-level units in Sichuan, characterized by diverse geomorphic types and stages of urbanization due to their location in the Hengduan Mountains. It elucidates the characteristics and evolutionary paths of urban forms based on different developmental bases, aiding in the analysis of urban expansion mechanisms. From 1990 to 2020, we quantitatively describe urban form characteristics using the two new indices alongside the landscape pattern index. Principal component analysis and hierarchical clustering are then employed to classify urban form types, revealing evolution patterns and trends across various landforms. The findings are as follows: (1) Urban forms in Sichuan are categorized into five types. Over time, nearly 81 % of clustered infill and compact adjoining cities are found in plains and hills, with the most compact forms in plains. As terrain gradient increase, urban patches become separated and fragmented, making compact forms hard to establish. About 83 % of dispersed sprawl cities, complex sprawl cities, and fragmented and dispersed cities are in mountains and plateaus. This reflects significant asynchrony in urban form evolutions across different landforms. (2) In 2020, urban form similarity between different landforms ranged from −0.35 to 0.38, indicating a low level. Over the past 30 years, Sichuan’s overall similarity index rose from 0.07 to 0.18, revealing a trend towards convergent urban form evolution. This study offers a nuanced understanding of the global dynamic features of urban expansion from a bottom-up perspective and reveals the gradient effect of landform on urban form evolution. It contributes to urban form research and provides a theoretical foundation for devising context-specific urban development policies for current and future scenarios.
