| Land utilization is the most direct reflection of human being's activities on the earth,and land cover change is the result of the long-term use of land utilization.Two of them have had a profound and direct influence on human's life and activities.Thus,it is significant to monitor the cover change of land utilization in real time,through which can learn its characteristics,regulars and process,make a reasonable adjustment for the way of land utilization,protect potential land resources and promote coordinated development between human social economy and ecological environment.This paper,based on remote sensing images in 1988,2002,2010 and 2014,taking Yubei District and Longquanyi District as the research area,performs image correction,image registration,image cutting,and image enhancement by remote sensing interpretation.Land use/cover in the research area is divided into six categories,including arable land,woodland,grassland,water,construction land and unused land according to the actual interpretable ability of the image and the land use/cover feature in research area.Land use/cover type's maps of the four periods in research area have been obtained by the combination of supervised classification and unsupervised classification,based on which we extracted data of the land use/cover changes in research area of the four periods.With using models including the change ranges,transition matrices,dynamic index,use intensity and comprehensive index of the land use,the land use/cover changes and spatial-temporal changes from 1988 to 2014 in research area were compared analyzed.Combining with the interpretation analysis results,by extracting information of urban built-up area in research area using NDBI method,we also compare and analyze the expansion features of build-up areas during 27 years from the aspects of the expansion speed,expansion intensity,compactness,fractal dimension and elasticity coefficient of urban built-up area.Finally,according to the actual situation of the research area,the evaluation index system of the urban build-up area expansion rationality was established to evaluate the rationality of the expansion of the built-up area.And the results are as follows.(1)Land use/cover change in the research area is obvious:Judged by the numbers,in Yubei District,the arable areas have decreased by 12114.37 hectares,the proportion has dropped from 42.13% to 33.82%,the woodland area has totally increased by 9064.57 hectares,the proportion has risen from 29.45% to 35.68%,and the construction land has had an increase of 3906.61 hectares in total for the 27 years,the proportion has risen from 20.32% to 23%.Meanwhile,in Longquanyi District,during 27 years,the arable areas have decreased by 8508.26 hectares,and the proportion has fallen from 42.08% to 26.76%,the woodland area has totally increased by 3302.78 hectares,the proportion has increased from 33.78% to 39.72%,and the construction land has increased by 5528.9 hectares,the proportion has arisen from 16.39% to 26.34%.To the point of using structure,the information entropy of land use structure in Two areas shows shows a tendency to rise first and then decrease in Four stages,the information entropy gradually increased from 1988 to 2010,indicating that with the increased of human activities on land use,the rapid advance of urbanization,the land use system is more and more disorder;the information entropy gradually decreased from 2010 to 2014,shows that in recent years,with the gradual improvement of the degree of land use planning rationality,urban development and planning is more scientific and reasonable,the land use system is gradually stable.From the perspective of land use degree,the four periods' results of the research area are above 270 and the differences are small,which indicates that on the whole the land use degree in the research area is high.(2)The significant expansion has happened to urban built-up area in research area:Judged by the expansion quantity,urban built-up area in Yubei District has increased by 17755.55 hm2 totally,with an expansion speed of 657.61hm2/a per year on average.The urban built-up area in Longquanyi District has increased by 10085.47hm2,with an expansion speed of 373.541hm2/a per year on average.The expansion intensity index of Yubei District and Longquanyi District were 4.51 and 6.72 respectively,which being in a high-speed expansion.Taking the expansion pattern as a standpoint,the compactness index of urban built-up area in research area has showed upward trend firstly,then downward,which manifested the changing process of urban built-up areas in the research area from a scattered state to a concentrated state and then to the relatively scattered state.Fractal dimension of Yubei District has offered a trend of rising first and then declining,indicating that urban built-up area is in a transition from external expansion to internal and edge filling.Fractal dimension of Longquanyi District has continued to rise,which shows urban built-up area is based more on external expansion on account of its terrain in plain region.Over the entire research period,expansion elastic coefficient of Yubei District is 1.21,the expansion of urban built-up area are in line with population growth,but it is still higher than reasonable value.Meanwhile,expansion elastic coefficient of Longquanyi District is 1.1,of which urban built-up area's expansion is in coordination with population growth.(3)The evaluation index system of the urban build-up area expansion rationality has been increasing:Establishing the evaluation index system of the urban build-up area rationality,which including economic,social,environmental and ecological benefits of four aspects,under the guidance of comprehensive,targeted and feasible principles.19 indicators were selected to build the system.It is turned out to be economic benefits of Yubei District has increased year after year,from 0.0408 in 1988 to 0.3971 in 2014.Social benefits increased from 0.0296 to 0.2645,environmental benefits increased from 0.0131 to 0.131 and the spatial structure benefits decreased from 0.1142 to 0.0755.The rationality of urban built-up area expansion increased from 0.1977 to 0.8680,the index increased by 3.4 times.Expansion of urban built-up areas is in line with the needs of land,which enhances the expansion and rationality.Economic benefit expansion of Longquanyi Distict built-up area increased obviously,from 0.0774 to 0.4002 in 2014.Social benefits rose slightly and increased from 0.0564 to 0.1772.Environmental benefits increased from 0.0117 to 0.1172.The spatial structure of benefit has showed upward trend firstly,then downward,which increased from 0.1142 to 0.1325,and then decreased to 0.0747.The expansion of reasonable degree increased from 0.2252 to 0.7693,the index increased by 2.4 times.The expansion growth rate of urban built-up area in four periods was reasonably well balanced.(4)The expansion pattern comparison of urban built-up area in research area:The expansion of urban built-up area in research area shows different modes due to the differences in geographic environment,social economy,traffic development,industrial structure and so on.With an undulating geography and a weak ecological environment,the YuBei District possesses fewer potential land resources,All of these efforts made by Yu Bei District government generate a JiangBei Airport Station-centered and airport-logistics-based industrial such as international commercial industry,modern logistics industry,hotel exhibition industry,ecological livable industry and fashion tourism through using the advantages of waterway transport to attract essential productive factors such as fund,technology,labor and information,forming the model of ?Airport development model?.The advantage of this model is that leading industry apparently,industry is positionded clearly,has a strong directivity,and the way of intensive land economical utilization can alleviate the contradiction between economic growth and a limited supply of land resources.Located in transitional zone from plain to hilly land,the available construction land resources in Longquanyi District is very rich,with the flat and opened terrain conditions,land resources is abundant,in the process of urban development,selectivity of industry development is bigger,gathering projects of automobile and key parts and engineering machinery,building industrial structure,which taking traditional automobile industry,new-energy automobile industry and new material industry as the leading factor while putting electronic components,machinery,pharmaceutical manufacturing and food processing as supplement,forming the model of ?Balanced development model?.The advantage of this model is that comprehensive,diversified industrial pattern,not only can promote the development of industry cluster,extend the industrial chain,but also enlarge the advantage of industrial cluster,by optimizing the environment of industrial development,Construct the first-class economic development zone.By developmenting of automobile manufacture,key parts and components production,tourism,convention and exhibition industry and the real estate industry,etc,we can promote the coordination of comprehensive development of the three industries,promot the optimization of economic structure in the studied area,speed up the development of modern industry. |
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