Study On Kashgar Urban Expansion And Cropland Changes Based On RS And GIS

In recent years, the rapid development in social economy，a phenomenal increase inpopulation, rapid expansion in the land use of urban construction, large-scale farmlandcultivation, and the great change in urban land use pattern have resulted in an ever increasingcontradiction between urban expansion and decrease in arable land. Urban expansion isconsidered as one of the most obvious spatial characteristics of urbanization. The study area ofthis paper is Kashgar-a city located in the south part of Xinjiang, China. The arid climate,hydrological environment and the rapid development of Kashgar have further deteriorated theproblem of arable land decrease and water resource shortage. These problems have seriouslyaffected the evolution of the living environment and the sustainable development of the localarea and the entire region of Xinjiang.By conducting a field investigation in the local area, studying the current situation of thelocal urban land use and collecting relevant historical materials, which have gained a ratherrich amount of data and graphic documents, and thus provided my paper with a good data base.Due to the influence of natural factors, human social economy and policy, urban land use andthe land coverage are constantly changing, and thus have become the important influentialfactors of area urban expansion and arable land change. This paper has chosen Kashgar city asa case study, Land sat MSS/TM/ETM+satellite remote sensing images as data source, andused decision tree classification method for extracting information regarding construction land,arable land, water body, woodland and unused land. By introducing indexes such as urbanexpansion intensity, extension rate, bar centric coordinates, compactness, elasticity coefficient,the change rate of arable land area, dynamic degree, and using analytical methods assuperposition and transition matrix, this paper has studied the space-time law of the Kashgarcity’s expansion, configurationally characteristics, and arable land characteristics. In addition,it has also studied hot issues such as current urban expansion and arable land change-area scaleurban expansion and arable land change. Finally, it has predicted the relationship betweenurban expansion and the variation of ecological factors in Kashgar in2030by using ecologicalconstraint model. The results show that:(1)The city construction land area has increased substantially in the past thirty-eight years.The divided six time periods from1972to2010possess urban area as8.18,8.31,25.78,32.88,42.41,51.33km2respectively. From1972to2010, the land use type transition area size arerespectively arable land>unused land>woodland> water body; Transition matrix results showthat the extended area of the construction land use was mainly resulted from arable landtransforming into construction land from1972to2010. (2) The changing trend of the extension rate and the extension strength transforming intoconstruction land use are basically the same. Extension strength demonstrated minimum valuebetween1972and1977, and maximum value between1977and1990. From2000to2010, theextension rate was steadily in the rise. From1972to2010, other than a slight expansion fromsouth to north, the city mostly had planar expansion towards west and east.(3) The configurationally characteristics of the city: compact degree from1972to2010was in a steady fall. Compactness reduces the only0.02between1972and1977, little change,And began to fell rapidly in1977-2010, compact reduce to0.34in2010.From1977to2010,the city construction land space axially outward rapid expansion phase, therefore, apredominantly peripheral contour compactness decreases; Rapidly rising fractal dimensionbetween1977and2005, the city space form this time irregular degree increase, urban spaceincreasingly complex. Fractal dimension between2005and2010not change, suggesting thatthis period of time city into the relatively stable stage of development.(4) From1977to1990and from2000to2005, the elasticity coefficient value was ratherhigh; urban expansion in this time period is relatively strong, city to accelerate the extension,the urban growth and uncoordinated phenomenon between the population growths.1972-1977,1990-2000,2000-2010and elastic coefficient value is low, the urban expansion is relativelyweak, effectively improve the not harmonious relationship between urban expansion andpopulation growth.(5) From1972to2010, the arable land in Kashgar has experienced a change fromdecrease to increase. The arable land size per capita has decreased gradually. The volatilitychanges of the added value leads to instability in the annual changing rate of the cultivated land.From1972to2010, most of the cultivated land turned into the construction land and gardens,but because of the cultivated land protection policies presented by the country and rises inprices, the merchants’ and farmers’ investment in the land reclamation resulted in the gradualgrowth in the cultivated land. During the whole research, the center of the cultivated landshifted in the direction of NE, NW and W.(6) From ecological constraints model we know that Kashgar city’s urban expansion hasgreatly influenced the ecological factors, especially the change of main ecological factors ofthe cultivated land. In theory, the bottom line of the urban expansion area under the ecologicalrestriction from2010to2030is calculated. This will have a certain application value for theurban plan of Kashgar city.