Characteristics And Evolution Of Settlement Size Structure In Suzhou, Wuxi, And Changzhou Area Of East China

Urbanization is an important aspect of global land use/cover change and it has an enormous influence of the composition, structure and function of ecosystems. Studying the pattern of urban system to reveal the law of urbanization process is the main way to study urbanization in landscape scale. Spatial Information Technology, such as RS and GIS, can monitor the urban spatial expansion efficiently. Urbanization process mainly manifests as the transformation of the other land use types to settlement. City settlement size structure presents as the composition and structure of settlement patches of different size in the settlement system, and it reflects urban spatial structure. In general, we can use hierarchical size structure and rank-size rule to describe settlement size structure. Cities in different area or in different developing process generally have some certain difference. Settlement size structure can be divided into two types, which are equilibrium distribution and non-equilibrium distribution, and primate city distribution is one kind of the non-equilibrium distribution. Studying the settlement size structure and its evolution rule will help to understand the urbanization process and the dynamic of urban landscape pattern, and will help to further understand the rule of urbanization.Suzhou, Wuxi and Changzhou area is located in the Yangtze River Delta, where both economy and culture develop fast. Suzhou, Wuxi and Changzhou area is one of the regions that have a high level of urbanization and the most intensive distribution of towns, and is one of the regions that have the most dramatic process of urbanization in our country. The fast urbanization process induces a great change in the urban landscape pattern. Studying the dynamic of settlement during urbanization process in Suzhou, Wuxi and Changzhou area has some reference value to the study of urbanization in our country.To reveal the regularity of the differentiated growth rate of settlement and settlement size structure and its evolution in the rapid urbanization process in both regional and county scales, we extracted the spatial distribution of the settlements in Suzhou, Wuxi and Changzhou area (3 prefecture-level units and 9 county-level units), by using the Landsat TM/ETM+images acquired in 1987,1993,1999,2005 and 2011. We analyzed the rank-size structure of both the whole area and each administrative unit. The patterns and dynamics of size structure of the settlement were studied by classifying the settlement patches into 8 size classes (<5,5-20,20-80,80-320, 320-1280,1280-5120,5120-20480, and ≥20480 hm2). The results showed that:1) The settlements expanded by 5 times in total size during 1987-2011. Temporal patterns of settlement growth varied among the administrative units, showing different growth rhythms. GDP of each administrative unit grows fast in an exponential form. The settlement sprawl intensity index has a different rhythm with the GDP relatively growth rate.2) Both the whole area and each administrative unit fitted Zipf’s law well. The number of the patches whose size is larger than 10ha increases during 1987 to 2005 in the whole area, and declines from 2005 to 2011. Zipf dimension of the whole area and each administrative increases continuously, and size difference among different settlements became bigger.3) The highest size class was promoted by 1-2 level(s); the proportion of the lowest size class reduced significantly; and that of the highest size class increased continuously. Additionally, the second-highest size class presented very small proportions (even 0) in three prefecture-level units and some county-level units.4) The equilibrium degree of the prefecture-level units was low and it decreased continuously, showed an equilibrium distribution; but the equilibrium degree of the most county-level units was relatively high and it had a rising trend, showed a non-equilibrium distribution.In general, size difference among different settlements became bigger in Suzhou, Wuxi and Changzhou area. The equilibrium degree of the prefecture-level cities was low, but that of the county-level cities was relatively high. By comparing the location condition and the landscape resource pattern in both equilibrium distribution units and non-equilibrium distribution units, we found that the resource distribution pattern could be an important factor influencing the size structure of the settlement and its evolution.