基于顶点城市的三角洲双核型空间结构形成演化研究

THE FORMATION AND EVOLUTION OF DUAL-NUCLEI STRUCTURE IN DELTA——BASED ON THE APEX CITY

三角洲顶点城市是基于城市区位和三角洲自然环境演变特征而提出的经济地理概念,此类城市的存在具有一定的广泛性。在多个三角洲,此类城市与门户港城之间由多种运输方式连接,形成了三角洲顶点城市-门户城市这样一种新型的双核型空间结构空间组合类型,并且,该双核结构沿线经济要素密集,是三角洲区域经济发展的首要轴线。基于对我国多个三角洲的实证分析,提出了此类双核型空间结构的广泛存在性,认为其形成伴随着海岸线变迁等三角洲自然环境要素的演化,并且,在这一双核型空间结构形成演化进程中,部分三角洲顶点城市经历了区域功能和地位的转化,现代开放经济条件下,作为三角洲门户的港口城市往往在短时间内超越了顶点城市。在此基础上,本文探索了三角洲双核型空间结构的形成机理,对其形成演化的进程进行了归纳总结。

The conception of the apex city of delta belongs to the field of economic geography, which is put forward based on the city location and the natural environment evolution of delta. It is discovered that this kind of city universally exists in many deltas. In these deltas, the apex city and the port city are connected by many types of transportation patterns, thus the dual-nuclei structure composed by these two kinds of cities is formed. In this paper, the author points out fast that the apex city- port city dual-nuclei structure is a new spatial structure. Also, this kind of spatial structure is the principal regional economic axes of the delta and the economic elements are centralized along the transportation line between the two dominating cites. And the author illustrates that the apex city-port city dual-nuclei structure is a common phenomena through contrastive case analysis on many deltas. Also, the author in this paper, puts forward that the formation of this spatial structure is companied with the evolution of natural environment in delta, for instance, the evolution of coastline. Based on the analysis above and the known spatial centralization patterns, the author divides the formation process of the apex city - port city dual-nuclei structure into two types the endogenetic and the ectogenic. The development of domestic delta is driven by endogenetic force. The dual-nuclei structure composed by apex city and the port city has been developing along with the evolution of physical environment of delta, which could be dassified into five phases during this process： the germination period of cities in apex region, the competition period of apex city, the fast development period of cities in delta, the formation period of the port city and dual-nuclei structure, the maturation period of the dual-nuclei structure, and so on. At last, the author believes that in the process mentioned above, the gateway of the delta was changed from the apex region to the coastal region, and the importance of the apex city declined gradually, compared with the port city. While in the dual-nuclei structure driven by ectogenic force, the apex city did not experience the deelining and function changing process, but it was impacted by the port city originally. Therefore, there are large differences between the apex city and the port city in this type of dual-nuclei structure, such as the city＇s size and the importance.