Characteristics and performance of urban-rural integration networks in cross-border areas of metropolitan region from the perspective of flow-form coupling: A case study of the Changsha-Zhuzhou-Xiangtan green heart area

The urban-rural integration in cross-border areas of metropolitan regions faces challenges stemming from mismatched endowment allocations and constrained cross-border factor flows. The flow space is playing an increasingly dominant role in resource allocation and spatial organization. Drawing upon the perspective of flow-form coupling, this study constructs an assessment framework to evaluate the performance of urban-rural integration networks, encompassing three core modules: identification of urban and rural endowments, construction of functional-spatial connection networks, and spatial pattern performance assessment. An empirical analysis is conducted in the Changsha-Zhuzhou-Xiangtan green heart area (CZTGHA). The findings reveal the following: (1) The precise functional complementarity and free exchange of elements constitute the two most critical relational mechanisms driving urban-rural integration in cross-border regions of metropolitan areas, giving rise to a flow-form dual structure encompassing both functional linkages and spatial configurations. The coordinated evolution and deep coupling of these mechanisms fundamentally shape the spatial performance of urban-rural integration. (2) Urban endowments exhibit a pronounced multi-polar and networked development trend, whereas rural endowments have experienced significant decline in peri-urban zones and along regional development corridors, with a tendency toward homogenized development paths. (3) Urban-rural spatial linkages in the study area are characterized by imbalance, and cross-border functional interactions between urban and rural areas face administrative boundary constraints, presenting a core-periphery pattern. (4) The performance of urban-rural integration in the CZTGHA is markedly higher than that observed in peripheral rural units. In 2024, 64% of spatial units in the study area were constrained by weak spatial linkages, while 52% suffered from inadequate functional connections. Flow-form mismatch constitutes a fundamental cause underlying the low urban-rural integration performance in these marginal areas. This research contributes theoretically to enriching the understanding of the inherent laws governing urban-rural integration, as well as provides epistemological and methodological references for the territorial spatial governance of metropolitan areas.