Analysis on regional structure and spatial characteristics of oasis urban agglomerations ZHANG Yu-fang YANG De-gang Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences

Outline Study background and meaning Material and methodology Objectives Results and analysis Conclusions and suggestion

Study background and meaning Optimization of geographic spatial structure is a main content of studying urban sustainable development. The study just focus on the inside structure of single city or urban agglomerations in developed region. The urban agglomerations on the northern slope of the Tianshan Mountains is a central area of Xinjiang and plays a decisive role in social and economic development of the region. The economic development is fast and promising. Understanding of the spatial structure of oasis urban agglomerations is very necessary and meaningful for promoting the development of this area.

Study background and meaning Eight cities: Urumqi, Miquan, Fukang, Changji, Shihezi, Kuytun, Karamay, Usu

Material The data of the urban work force and population from Urban Statistical Yearbook of China from 1991~2001 Statistical yearbook of Xinjiang from 1991, 2001, 2006 Commuting distance between cities Digital elevation map and Landsat ETM images(2000) of the northern slope of the Tianshan Mountains Material and methodology

Methodology Fractal theory A branch of nonlinear science and an important means for science research. An effective methodology on studying the urban systems of the city geography. To reveal the geographic spatial structures. Zipf dimension Space relation fractal dimension The method to classify city function Using data of the urban work force structure, statistical analysis, combining J. W. Maxwell and H. J. Nelson's the city classification methods, the authors reveal the urban functional structural characte - ristics from 1990 to Material and methodology

Objectives To analyze the development route of oasis urban agglomerations from 1990 to 2005 including the temporal-spatial feature of size the structure urban functional changes the macroscopic distribution and microstructure interaction characteristics To discuss the optimization method of geographic spatial structure

Results and analysis The temporal-spatial feature of size The urban primacy index is higher than normal level (Fig1a), and the concentration effect of main city plays dominant role. But it decreasing gradually, the distribution of population is less concentrated through the period (Fig1b). The city hierarchical structure has changed. Fig1. The changes of urban primacy index (a) and population distribution curve (b) unit: ten thousand of urban agglomerations at the northern slope of the Tianshan Mountains

Results and analysis The temporal-spatial feature of size Based on the fractal theory, the fractal dimension of the scale structure was calculated with Zipf rule in study region. (1) When D< 1, the distribution of population is uneven and the system is underdeveloped When D> 1 ， more medium-sized cities in the urban scale distribution, population distribution is more balanced and the system of urban agglomeration is developed [4] [13] [18] 。

Results and analysis The temporal-spatial feature of size It was found this region’s urban systems have the fractal properties. With the rapid development of economy, the urbanization process accelerated from 1990 ～ 2000, the uneven distribution of population was enhanced ； When Shihezi city became a new economic core, the effect of polarization population was decreased from 2000 to Fig2. The ln-ln plot of the urban system-size distribution in the Urban Agglomerations at the northern slope of the Tianshan Mountains

Results and analysis The urban functional structure changes Using data of the urban work force structure, statistical analysis, combining J. W. Maxwell and H. J. Nelson's the city classification methods, the authors reveal the urban functional structural characteristics from 1990 to Table1 ． The categorization of national industries classification DepartmentIndusryDepartmentIndusry Construction TransportationTransport, Storage and Post Business Wholesale and Retail Trades Administration Public Management and Social Organizations Hotels and Catering Services Water Conservancy, Environment and Public Facility Management Industial Mining Service Services to households and Other Services Production and Distribution of Electricity,Gas and Water Scientific Research, Technology Service and Geological Prospecting ManufacturingInformation Transmission,Computer Servcie and Software Education, sciecen,culture and health EducationReal Estate Health, Social Security and Social Welfare Financial Intermediation Culture, Sports and Entertainment Leasing and Business Services

Results and analysis Table2. The industrial location entropy of urban agglomerations at the northern slope of the Tianshan Mountains in 1990 and 2005 City Construction Transportation Business Administration IndustialServiceEducation and science Urumqi Shihezi Kuytun Miquan Fukang Karamay Usu The structure urban functional changes

Table3. The functional structure changes of urban agglomerations at the northern slope of the Tianshan Mountains in 1990 and 2005 City Dominant functionLeading function UrumqiIndustrial Transportation ConstructionServices ShiheziIndustrial Construction KaramayIndustrial FukangIndustrial Administration Education and science ChangjiIndustrial Construction Administration Services MiquanIndustrialConstruction Industrial Construction Services Construction KuytunIndustrialBusiness Industrial Transportation ConstructionBusiness UsuIndustrial Transportation Business

Results and analysis The urban functional structure changes Using data of the urban work force structure, statistical analysis, combining J. W. Maxwell and H. J. Nelson's the city classification methods, the authors reveal the urban functional structural characteristics from 1990 to The urban economic structure is similar that the leading sector is industry and sectors with superiority are transportation and business industry. But the dominate function became diversified.

Results and analysis The macroscopic distribution characteristics The city always along with oasis, road and railway(Fig3a) 。 （ 1 ） Be near the watershed of the mountain systems and lies on the upstream of piedmont alluvial-pluvial fan which is rich in water resource, plantation and good at soil texture. Where is oasis and where is city. （ 2 ） The water resource and rivers distribution impact on the urban expansion direction and the shape of the oasis city significantly. The urban expansion direction is along the river basin. The shape of the city is long strip which the length is more than broad 。

Results and analysis The macroscopic distribution characteristics No matter in ancient times or in the contemporary era, the traffic impact deeply and significantly on the congregation, interaction and distribution of the oasis city. Based on the methods of Hausdorff fractal dimension and space relation fractal dimension, the paper adopt calculation models on the fractal dimension and the arriving degree of road network. (2) r is radial distance, When D→1 ， Many elements of the city system are concentrated on single geographical elements such as river, railway ; When D→2 ， the distribution of city is even [4] 。 When r’ is communication distance, :arriving degree of network, when it close to 1 ， the capacity of urban transportation is better ， and the correlation of elements between cities is stronger.

Results and analysis The macroscopic distribution characteristics （ 3 ） The traffic artery become another element impacting the distribution of oasis cities. In the study area, the city density is relatively high, the communication is very well and approximately straight line form 。 Fig3 The ln-ln plot on the spatial distribution of 8 main cities at the northern slope of the Tianshan Mountains

Results and analysis The macroscopic distribution characteristics Fig4. City group distribution (a) and spatial structure (b) of urban agglomerations at the northern slope of theTianshan Mountains

Results and analysis The microstructure interaction characteristics Spatial structure of regional economy characteristic ： Fig4. City group distribution (a) and spatial structure (b) of urban agglomerations at the northern slope of the Tianshan Mountains The whole shape : “Dumbbell” Two main economic cores: Urumqi metropolitan Areas Economic zone of Kuytun, Usu and Dushanzi Another is growing: Economic region of oasis urban groups including Shihezi city ， Shawan county and Manasi county

Conclusions and suggestion （ 1 ） The rank-scale distribution and spatial interaction has fractal character. （ 2 ） The feature of hierarchical structure is loosing, primate city distribution, and the uneven population distribution. But from , the population centre changed from single to multi-center. （ 3 ） However the functional division in urban agglomerations is not very distinctness. The urban economic structure is similar that the leading sector is industrial. The urban functional structure is developing and perfecting and the dominate function became diversified.

Conclusions and suggestion （ 4 ） The spatial distribution is linear ， and the mostly cities lie on a geographic element as rivers, railway and national artery ； The connectivity degree is relatively strong. The display of spatial organizational structure is belt, integration of partial and whole, concentration of megalopolis and economic zone. （ 5 ） According to the conditions of resources and situation of development, the developmental strategy should be as follows: To give priority to develop new sub-central cities such as Usu, Fukang, To accelerate the national city-Urumqi, entirely play roles of radiation of central cities. To pay more attention to develop the diversification of urban function

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