| During recent years, with the rapid growth of population and constant improvement of social and economic development, the urbanization process is quickly accelerated. Great changes have taken place in city land use pattern at the same time. Expansion of construction land and decrease of agricultural land area have become the most important feature of land use change. Linyi City, a typical city in Shandong Province, is in the stage of increasing demand for construction land. How to promote coordinated and sustainable development of population, resource and environment has become an urgent problem. Study on the temporal and spatial characteristic of urban expansion and its driving mechanism, is of great realistic significance to the control of huge and irrational expansion of construction land, the protection of farm land and ease the pressure on the demand for land during urban construction, which is ultimately helpful to achieve the fundamental goal of sustainable development of economy, society and ecology.Taking Linyi city as the case study, including Lanshan District, Luozhuang District and Hedong District,1990,2000,2010 Landsat TM images captured based on RS, GIS software platform were used as the original data. Combined with supervised classification and visual interpretation, the classification of land use data of 1990,2000,2010 is acquired. Firstly, transfer matrix of land use, dynamic degree of land use land use, the landscape pattern index were used to analyse the general characteristics of spatial pattern of land use change during the past 20 years. Then the temporal and spatial characteristics of land use changes from 1990 to 2010 were analyzed from different points of view, using methods like different parameters of urban expans, spatial gradient model, space focus migration model, extension form, and expansion types and so on. On that basis, social and economic data of the study area wered collected to qualitatively and quantitatively analyse the driving force mechanism of urban expansion form the natural and social aspects. In the end, the CA-Markov model was used to simulate the land use spatial pattern and predict the future 10 years land cover data. The main conclusions of this research were:(1) During the past 20 years (1990-2010), the land use structure of Linyi City has changed significantly. On one hand, the built-up land area has increased by 29488.7 ha while the cultivated land has decreased by 25113.19 ha, on the other hand, the forest land and unused land decreased at different levels. Becides, the grassland area showed fluctuation, increased firstly and then decreased. The water area decreased slightly. In combination with landscape index, the urban landscape of Linyi Cinty is moving steadily closer to fragmentation. The farmland fragmentation is becoming more serious and the patch size of construction land is becoming bigger.(2) There is an obvious temporal and spatial differentiation of Linyi City. The annual growth rate of built-up land area in 2000-2010 was far higher than that in 1990-2000, meanwhile, the expansion dynamic degree and intensity were significantly increased. From the propagation direction, during the period of 1990 to 2000, the construction land extended from the city center to the direction of southwest and northwest. During 2000-2010, in addition to the previous trend of expansion, expansion rate and intensity were increased obviously in the Southeast direction. According to the spatial gradient model, The maximum peak of urban construction land expansion capacity appeared in the range of 5-7.5km far away from the city center. The city construction land is expanding from the city center to the direction of southwest and northwest.(3) From the growth morphology of city construction land, Compactness index decreased slightly. It is concluded that the city is relatively compact, but it has the trend to be loose over time because of the distribution of built-up land during city expansion. On the other hand, the fractal dimension increased first and then decreased, the stability coefficient first decreased evidently, then a slight rebound in the last ten years, which showed that the city is becoming more regular and more stable on the whole. The calculation of landscape expansion index indicated that the construction land in Linyi City is given priority to large amount of small-scale adjacency expansion mode.(4) In consideration of social and economic statistic data of Linyi from 1990 to 2010, the driving factors of urban expansion can be divided into the following five aspects:natural environmental factors, economic factors, demographic factors, policy factors. Rapid economic development is the most direct and main power of urban expansion, also the government policy of Linyi City plays an important guiding role in the direction of city spatial expansion.(5) The CA-Markov Model was used to simulate and predicte the city spatial expansion of Linyi. Results showed that by 2020, according to current state of development, the area of construction land would continue to rapidly increase and its proportion would be as high as 38.75%. The area of cultivated land, forest land and unused land would reduce at different levels and the cultivated land decreased most significantly. Compared with the master plan of Linyi City, it was found that the increasing speed of construction land would be so high that its area would be much larger than its planning area while the area of cultivated land would be much smaller than its planning area. In view of the contradiction, the speed of urban development should be appropriately slow down and it is time to strengthen the intensive utilization of land and improve the efficiency of land use.The purpose of this paper is to explore and simulate the land use changes in the past and future. We hope the research conclusions could provide scientific basis for the urban growth management, planning, as well as social and economic sustainable development in the future in Linyi City. |
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