Temporal-Spatial Evolution Characteristics and Dynamic Mechanisms of Regional Cooperation Network in the Yangtze River Delta

The evolution and dynamics of regional cooperation are hot topics of concern for economic geographers. Regional cooperation has gradually evolved into a network structure based on "multi-dimensional connection," covering many fields such as economy, innovation, transportation, and ecology. However, most of the current research focuses on a specific cooperation field, mainly based on regional intergovernmental agreements, analyzing the structure and characteristics of regional cooperation networks from the perspective of institutional connections. This lacks a comprehensive measurement index system for regional cooperation levels using multidimensional connection data, and the dynamic factors and mechanisms of regional cooperation networks are unknown. Therefore, based on the relational perspective, this study constructs a comprehensive measurement index system of the regional cooperation level from the aspects of economy, innovation, transportation, and ecology and discusses the evolution characteristics and dynamic mechanisms of regional cooperation networks in the Yangtze River Delta at different stages using social networks and QAP analysis methods. The main findings are as follows. First, the regional cooperation network in the Yangtze River Delta is relatively close in general and has undergone a remarkable evolution process from loose to tight, from single center to multi-center, and from inefficient to efficient. The average path length of the regional cooperation network in the Yangtze River Delta has been declining, indicating that the regional cooperation network in the Yangtze River Delta presents the characteristics of "small world." Secondly, the main body of the Yangtze River Delta regional cooperation network shows obvious "multi-center, flat" characteristics, forming a spatial structure supported by the "golden triangle" of Nanjing-Shanghai-Hangzhou and gradually spreading to neighboring cities. Core cities such as Shanghai, Nanjing, and Suzhou played important roles in different stages. During the initial stage of collaboration, Shanghai served as the central hub, with Suzhou and Nanjing acting as key nodes. During the phase of rapid intensification, the network evolved into a dual-core system centered on Shanghai and Nanjing. During the high-quality development phase, a multi-center interactive pattern emerged, involving Shanghai, Suzhou, Nanjing, and Hangzhou. Additionally, geographical and institutional proximity significantly influence regional cooperation in the Yangtze River Delta.The changes in the economic development level based on cognitive proximity and cooperation reflect the dynamic adjustment of the economic and industrial structure in the region, which has stage differences. During the early stages of regional cooperation, cognitive proximity significantly promoted regional cooperation. Subsequently, the role of cognitive proximity decreased, and with the deepening of cooperation during a period of high-quality integration, cognitive proximity played a significant role. In addition, government support played a significant role in promoting regional cooperation during the early stages but its importance declined as cooperation deepened. Compared with existing research, this study comprehensively constructs a measurement system of regional cooperation in the Yangtze River Delta from four dimensions: economy, innovation, transportation, and ecology, which is an expansion of the single measurement system of existing research and more comprehensively reflects the characteristics of regional cooperation in the region. Through this study, we hope to overcome the limitations of studying one-dimensional cooperation and further enrich and improve the relevant theoretical system of regional cooperation. Through this study, we hope to overcome the limitations of studying one-dimensional cooperation and further enrich and improve the relevant theoretical system of regional cooperation.