Abstract:

Based on big data for rail passenger transportation, this paper explores the spatial linkages among three major urban agglomerations of the Yangtze River Economic Belt, Including the Yangtze River Delta,the Middle Reaches of the Yangtze River City Agglomeration and the Chengdu-Chongqing City Agglomeration, as well as their spatial structural heterogeneity, from the intra- and extra-group perspectives. The results show that: ① The three major city agglomerations have stronger in-group links than out-group. There are predominantly intra-provincial links in both the Yangtze River Delta and the Middle Reaches of the Yangtze River City Agglomeration. The Chengdu-Chongqing city agglomeration has stronger inter-provincial links than intra-provincial links. However, the intensity of inter-provincial links within the three city agglomerations is much higher than that outside the agglomerations, implying that under the effect of the mechanism of internal agglomeration, cities within the city agglomerations are more likely to break through the provincial boundaries to create links and realize the integrated development of the region. ② The intensity of intra-cluster and extra-cluster linkages of large city clusters reaches its highest at inter-city distances of 0-100 km and 0-300 km, respectively. And the intensity of in-group and out-group links between cities in the Yangtze River Delta and the Middle Reaches of the Yangtze River city agglomerations follow the law of distance decay, but in the Chengdu-Chongqing city agglomeration, only the out-group linkage conforms to this law. ③ Megacities dominate the in-group and out-group links of the three major urban agglomerations. In the in-group and out-group links, the urban connection intensity of the three major urban agglomerations at the same level is proportional to the city size, while the cross-level urban connection intensity is inversely proportional to the series difference. ④ The spatial structures of the Yangtze River Delta and the Middle Reaches of the Yangtze River City Agglomeration are polycentric, though the extra-cluster linkages have a reinforcing effect on the polycentric structure of the former. The Chengdu-Chongqing City Agglomeration has a "single-core" form in the view of intra-group linkage, and a "double-core" structure in the view of extra-group linkage and total linkage, indicating that the extra-group linkage is pushing the Chengdu-Chongqing City Agglomeration to change from a "single-center" to a "double-center" structure.

Key words: urban agglomeration, spatial correlation, spatial structure, railway passenger traffic flow, the Yangtze River Economic Belt

摘要：

城市空间联系是城市群形态发育的基础。基于铁路客运大数据，从群内、群外视角探究长江经济带长三角、长江中游和成渝三大城市群的空间联系及其空间结构异质性，主要结论如下：①三大城市群的群内联系均强于群外联系，长三角、长江中游城市群的内外联系均以省内联系为主，但由于重庆直辖市对周边四川省所辖城市的强吸作用，使得成渝城市群群内联系中的跨省联系强于省内联系；但三大城市群的群内跨省联系强度远高于群外的跨省联系，意味着在内聚机制作用下，城市群内的城市更容易突破省界阻隔发生联系，实现区域一体化发展。②三大城市群的群内、群外联系强度分别在城市间距离0~100 km、0~300 km时达到最高，而且长三角、长江中游城市群的城市间内外联系强度均遵循距离衰减律，但成渝城市群只有群外联系符合这一规律。③超大特大城市均主导着三大城市群的内外联系，相同等级城市间联系强度均与城市规模呈正比，形成“强强联合”效应，而跨级城市间联系强度与级数差呈反向变化。④在群内、群外及总联系视域下，长三角和长江中游城市群的空间结构均呈多中心结构，不过，群外联系对前者的多中心结构具有强化作用，对后者却表现出一定的削弱作用；而成渝城市群在群内联系视域下呈“单核”形态，群外联系和总联系视域下均为“双核”结构，说明群外联系具有推动成渝城市群由“单中心”向“双中心”结构转变的功能。

关键词: 城市群, 空间联系, 空间结构, 铁路客运流, 长江经济带