The Research Of Expansion Mode In The Urban Fringe Of Harbin Based On The Construction Land And The Landscape Patterns

The urban space expansion is the core problem of urban geography and land science studies.Researching the space extraction method, space characteristic, expansion mode and driving factors of the urban fringe, can help us to directly understand the evolution process of the formation and development about the urban spatial structure, and effectively control the spreading of urban space.At first, using Landsat TM data in 1991, 2000, 2010 and 2015, We obtained four periods of the vector data about the construction land of Harbin City. Then, we tried to construct two kinds of space extraction model of urban fringe. The first one was “sliding cutting” model, which is more simple and feasible, from the construction proportion change perspective. We used this model to extract the boundaries of the core-area, the inner-fringe and the outer-fringe, by setting extraction threshold. And then we explored the spatial changes of the urban fringe. At the same time, we built the other model from the landscape pattern perspective, which was according to the trend of the fragmentation trend of landscape patches of the construction land. And on this basis, we bordered the outer edge of the urban fringe, taking advantage of “BASS diffusing”, named shortly as the BASS model in the following content. Further we discussed and analyzed the change process of the landscape shape and the size of the urban fringe, from the overall level and plaque level.Proceeding to the next step, we advanced the theory assumption of the expansion mode of the urban fringe, in line with the results of the extraction by two models and the fragmentation trend of urban fringe landscape, and then we did the empirical analysis. Finally, we generalized the main driving factors of the development on the urban fringe of Harbin city, from three aspects were policy supporting, traffic pulling and social economy.The results showed:(1) Instance analysis made clear that the extraction models of urban fringe structured from two perspectives not only had strong feasibility, but also reflected the city expanding circle’s characteristics, which were centrality and directivity. The result abstracted by one of the model,“sliding cutting”, built from the perspective of construction land proportion change, which was not only in conformity with the traffic network of Harbin city, but also clearly reflected the space developing direction of the urban fringe, had strong practicality. And the other one, constructed from the view of landscape pattern, is consistent with the inner circle of the three circle-layers in the urban system of Harbin “twelfth five-year” planning. The result not only certifiedquantitatively that the three circle-layers in the urban system of the development strategy, which proposed in Harbin planning, was feasible, but also specifically quantified the range of the inner circle in Harbin. This had cracking guiding significance, to clear and define the external boundary of the spatial expansion in Harbin.(2) The research of the urban fringe in Harbin, from the perspective of the construction land proportion change and the landscape pattern, showed that the development of the urban fringe was closely related to the periodic fluctuation for the social economic growth. In the stage of slow urbanization(1991-2000) in Harbin, the urban fringe was in stable condition, whose spatial location and the shape and size of the construction land patches were little change. However, in the stage of rapid urbanization(2000-2015), the urban fringe, whose the space position moved southwest, and whose area increased rapidly, was gradually coincided basically with the inner circle of the urban system in Harbin. At the same time, the construction land patch area was also increasing, the patch shape was becoming more and more irregular.(3) The space characteristics of urban fringe, based on the construction land proportion change, showed that the center of Harbin city, in the past 25 years, totally, moved to southwest direction. Especially, it moved more quickly, in the stage of rapid urbanization(2000-2015). The shape of the core area in Harbin, from 1991 to 2015, was from "heart-shape" gradually to regular shape. And during the same period the extent of the core-area was within the second ring road,extending step by step to between the second and third ring road. The extent of the inner-fringe also extended from within on Harbin belt highway(the fourth ring road) to the outside of Harbin belt highway. At the same time, the outer-fringe had apparently over the boundary of the study area.While, in terms of the expansion speed, the stage of slow urbanization(1991-2000) was greater than the stage of rapid urbanization(2000-2015), compared the expansion speed of the core-area.But the stage of rapid urbanization was greater than the stage of slow urbanization, compared the expansion speed of the inner-fringe and the outer-fringe. Wholly, the expansion speed of the inner-fringe was the fastest, the outer-fringe took the second place, and the core-area was the slowest.(4) The landscape characteristics analysis of the urban fringe, based on the view of landscape pattern, showed that: in the stage of slow urbanization(1991-2000), the urban fringe was relatively stable, while in the stage of rapid urbanization(2000-2015), both the space position of the urban fringe moved southwest, and the area increased quickly; In the overall level, the stage of rapid urbanization was more quickly than the stage of slow urbanization, compared the expansion of the construction land. And the construction of the whole domain was the chief motive force. The advantage of the concentrated built-up area of city in the whole domain was relatively stable, and in the urban fringe was gradually declining; On the patch level, the area of the construction land patch mainly was concentrated in 0.01-1km2, which was more than fore-fifth of the total number of patches. However, the area of the construction land, in 0.01-1km2, in the domain and the urban fringe, was less than one-fifth of the total area of the construction land patches; On the whole,construction land patches were scattered layout in Harbin city. In the stage of slow urbanization,the main of the expansion was the small patch. In the stage of rapid urbanization, the concentrated built-up area and other construction land were expanding at the same time. In addition, with the increasing of the patches, shapes of the patches were more and more irregular.(5) According to the extraction results of urban fringe by the sliding cutting model and BASS model, as well as the fragmentation degree of the landscape of the construction land in the urban fringe, the expansion modes of the urban fringe in this article were divided into four modes, which were “stable”, “extensional”, “jumping” and “mixing”. Although in the stage of slow urbanization(1991-2000) the urban fringe was relatively stable, there was still a trend, “stable” expansion mode gradually alternative to “jumping” and “mixing” expansion mode, and “jumping” expansion mode transforming to “mixing” expansion mode. And the boundary of four kinds of expansion mode were increasingly obscure. Nevertheless, in the stage of rapid urbanization(2000-2015), the fragmentation trend of construction land in the urban fringe increased, as a result of the different development strategy in different regions taken by government, and the different development strategy of the traffic infrastructure in the locational conditions. At the same time, because of above reasons, the development pattern was gradually presenting clearly from multiple modes coexisting. Thus on the whole, it gradually formed “jumping in the north, extension in the south,improvement in the east and expansion in the west”. Which means that “extensional” and“jumping” expansion mode was coexisting in the east and northeast, that the main of expansion mode in the southeast and the south was “extensional” and supplement was “jumping”, that the development was discrete mainly as “jumping” expansion mode in the northwest and the west.(6) Since 2000, under the jointly effect of the factors, which were policy supporting, traffic driving and social economic factors, the function pattern of the urban fringe was basically formed,which was “industry in the south, farming in the north, the commerce and the administration in the west and the east”. In other words, the industry, the commerce, the finance and the tourism were relatively concentrated in the south and southwest. The east and the northeast had strong agricultural characteristics, owing to gathering the agricultural industry parks, and existed the administration, the residence and the commerce in the meantime. The science and education, the administration, the commerce and the leisure were gathering in the west. Those factors,collectively and possibly, promoted the expansion process of the urban fringe in Harbin city, and drove the formation of urban spatial distribution pattern at present stage.