Land Cover Changes And Their Driving Forces Over The Last 40 Years In Jingtai Study Area, Gansu Province

Land cover changes from 1973 to 2014 and their driving forces were analyzed in this dissertation utilizing object based image analysis (OBIA) method for six scenes of Landsat MSS, TM, and OLI images. Rule sets for classification were constructed through the integration of decision tree into OBIA.This dissertation demonstrated that:(1) object-based image analysis in diverse combinations of segmentation parameter is easy to carry out by constructing an image-object hierarchical network of land cover extraction process. (2) the first step of land cover mapping was a bifurcation process to identifiy two general categories, namely vegetation and non vegetation. Then, the detailed classification of vegetation, specifically for sandy land, forest land, irrigated land, desert steppe and non vegetation. The latter was classified further into rural residential land, urban residential land, ponds, and so on. Selecting training samples to calculate the stay to classify objects into various types of separability size, distance, on samples were compared, easier to optimization of sample extraction results. At the same time, the combination of land cover information extraction based on image object spectral, spatial geometry and phase characteristics, can better improve the automation and intelligent level of information extraction. (3) the use of cart decision tree constructed more versatility and stability of classification rule set, according to characteristics of land cover in the study area are and get better classification results. (4) analysis of land cover in the study area is type area of annual variation rate, changes in different periods and the extent of land cover types of changes in the area, the land cover change trends are discussed. Area of cultivated land in Jingtai County in the year 1973-1988-1994 are increased in 1973-1988 years due to water enough, mainly for the increase of irrigated land, which by the desert grassland converted into irrigated ha 1910.73. In 1988-1994 years, mainly for the increase of sandy land. Desert steppe area is significantly reduced, and the corresponding is sandy land area increased and the desert grassland conversion into sands ha 538.3. Cultivated area in 1994-2001 also increased, mainly sandy land, woodland area increased significantly, which by desert steppe into sands 318.4 hectares, irrigated into sands 633.2 hectares, woodland conversion into 41.26 hectares orchard. At the same time, the urban residential land conversion from rural residential land conversion increased by 68.32 hectares. Arable land has no obvious increase in 2001-2006-2014 in the area, the forest area in 2006 woodland converted into 51.32 hectares orchard, the deadline of 2014 woodland conversion into orchard 63.58 hectares continued to increase. (5) According to the change of land cover in the study area, the driving force caused by the change occurred in the study area.. Is mainly due to"Jingtai Pumping Irrigation Project" for the development and construction of the representative of the water conservancy project can significantly improve the conditions of water resources supply, October 1969 the first phase of the project started construction, irrigation area of 202.8 million hectares. Two phase of the project started construction in July 1984, irrigation area of 34700 hectares. Jingtai County began early maturing potato, beer barley, maize seed, special corn, mountain green small grains, strong gluten wheat advantage in the production of planting industry, vigorously develop the outskirts of a city, in irrigation areas along the Yellow River fine vegetables. At the same time, the extension of the Caowotan, Shawo, diffuse water beach, red water of four towns of Chinese wolfberry industry zone, promote Zhongquan Xiang Mu planting dates. Jingdian second phase extension to Minqin water transfer project, started in 1995 and March 2001 began to Minqin water, irrigation area of 1.01 million hectares. Is from 2001 to 2006, the area of cultivated land to 6.93 million hectares, forest area reached 11.5 million hectares, on this basis and ponds. That start Jingdian project in March 2001 obtained abundant water resources along the highway 308 line to Minqin water diversion along the irrigable land, forest land, forest coverage rate reached 92.6%. At the same time, started the construction of high quality pear demonstration park, to promote the construction of three "fifty thousand acres" fruit base. The desert grassland has obviously decreased. By the end of 2014, agricultural taking the base construction and the characteristic agriculture is developing in the direction of, forming a base of 6 million mu of potato,3 million mu of the base of malting barley,6 million mu of fruit bases and desert potato, as early as pear, melon, then apricot, large plate of seeds and other characteristics of products, the cumulative production of 7751 million kilograms of grain,29.12 million kilograms of oil and other economic crops, Jingtai county is no longer drought control, full development of agriculture, get rid of the farmland barren state. On the other hand, social factors promote the economic development of the research area, thus promoting the land cover change of the study area.