基于复杂网络的长三角城市对外服务群落结构研究

城市群已成为国家参与全球竞争与国际分工的重要空间载体,其空间组织形式正从个体城市集聚、等级性的中心地结构向多中心、嵌套式的群落结构演变。为刻画长三角地区城市在不同要素层面下形成的多层次群落结构及其状态,借助复杂网络分析工具,从城市群落的节点特征、垂直和水平结构、不同群落结构间的相互关联三方面实证分析长三角地区3类(生产性、生活性、公共性)对外服务流的网络结构特征。研究显示:1)长三角城市节点服务功能分化,节点层级性分异显著,生产和生活性服务网络的节点规模呈"长尾"分布,公共性服务网络的节点规模相对均衡;2)垂直结构上,3类对外服务网络的网络密度、网络效率、流量占比和空间分布各不相同;水平结构上,初步形成对外服务网络的专业化分工格局,部分城市突破区域界线,呈跨地域集聚组团的态势。3)较强的结构关联性存在于生产性和生活性对外服务网络之间,两者在中低度值的城市节点上具有一致性,呈联动发展格局;公共性对外服务网络与前两者的节点度值分异较大,促进了整体群落服务功能结构的丰富和完善。基于复杂网络的群落研究可以从多维结构的分析中寻求城市群落的分工协作和共生,为当前多核心、网络化的城市空间组织与规划提供科学参考。

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 cross-region 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.