以城市体系与水系的分形结构相似性为实例,探讨人文地理系统与自然地理系统的对称性及其破缺特征。首先建立城市人口—河流长度、城区面积—流域面积、 (某一级别的 )城市数目— (某一等级的 )河流数目等测度对应关系 ;然后证明基于中心地理论的Beckmann城镇等级—规模模型与 Horton水系构成第一、第二定律数理同构,关于城市人口—城区面积的异速生长关系模型与关于主河道长度—流域面积的几何测度关系模型以及 Horton水系构成的第二、第三定律数理同构 ;进而提出 :城市体系与水系分形结构的相似性实质上是自然—人文地理系统的对称性,只是这种对称关系存在一定程度的破缺,地理系统的演化目标之一似乎是要重建大自然的对称律。
It is demonstrated in the paper that the cascade structure of river networks is analogous to that of urban systems or systems of central places, i.e.,the two kind of systems have the same fractal recurrence. Where mathematical models are concerned, the first and second ones of Horton’s laws of drainage composition is same to Beckmann’s models of city hierarchies which are based on central place theory; Hack’s law, which can be derived from the second and third Horton’s models, is same to allometric relationships between area and population of urban systems, the latter is connected with Beckmann’s models and thereby with central place theory. A conclusion can be drawed as follows: urban systems as well as central places are symmetrical with river networks, as is generalized, we have a conclusion that human geographical systems are symmetrical with physical geographical systems, with the symmetry breaking to some extent in some aspects.
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