Analysis of community structure in the Yangtze River Delta region: a case study of urban external services

Urban agglomeration is an important spatial carrier of social and economic activities in global competition and the international labor division. Accordingly,China’ s urban agglomeration is transforming from a traditional hierarchical structure to a complex and nested structure. To reveal the multi-level community structure in the Yangtze River Delta region,we first constructed three types of networks from different external service flows( producer,consumer,and public),and then conducted a Social Network Analysis to examine network structures and relationships among them. The research findings are threefold. First,service networks were constituted of different hierarchical structures. The node distribution in producer and consumer service networks was characterized by a long tail and high degree of differentiated outflow. Second,different types of service networks exhibited both vertical and horizontal differentiation. In vertical structure,the percentage of flow and spatial pattern at each level varied. In horizontal structure,an early form of external service specialization emerged among some cities,which have expanded beyond their geographical boundaries and showed a pattern of crossregion agglomeration. Third,there was a strong correlation between networks of producer and consumer services. Both types of networks showed consistency among medium-and low-grade nodes,indicating a mutual growth pattern. The structure of the public service network was different from the other two networks,which has enriched and strengthened the functions of urban communities. The results of this study can facilitate the understanding of the multi-dimensional structure of the urban community,and have useful implications for regional and urban planning and organization.