Title: Dynamic Changes In Land Use / Land Cover In Tongchuan, Shaanxi Province

Based on the TM remote sensing images in Tongchuan in the years of 1987, 1992 and 2002, dynamic changes of land use / land cover were analyzed. Combination with remote sensing technology and geographic information system, the essay extracted the land use type information using the method of supervised classification, and analyzed the quantity and spatial structure characteristics of land use in Tongchuan through a series of analysis, including land use / land cover transition matrix analysis, pattern analysis, landscape pattern analysis and land use change driving forces analysis. By indicating the driving factors of regional land use changes, the article aims to give corresponding evidences and suggestions to Tongchuan City on development plan, environmental protection and ecological building.Main land use types in Tongchuan were forest land, cropland, shrub forest and residential land, which can be seen from land use classification map. Forest land mainly focused on the northwest part of Ziwuling mountain; cropland located in the south, east and northern flat tableland areas; shrub forest located in the gully transition between forest land and cultivated land/grassland, residential land mainly distributed along the Paint River.Types of land use changed significantly in Tongchuan from 1987 to 2002: the reduction area of arable land accounts for 13.81% of the total area; shrubs and forest land increased 8.88% and 2.33% of the total area; arable land, shrub land and forest land became the main change types of land use.Orchards, residential areas, farmland, forest land, shrub land became the main types of land-use conversion in the 15 years, of which farmland reduced by 542.45 km2, and mainly converted to forest land, shrub forest and residential land. Forest area and shrub forest area increased by 91.44 km2 and 349.05 km2 respectively. Tongchuan's vegetation cover (including forest, shrub, and grass) ratio increased from 54.52% in 1987 to 64.46% in 2002, an increase of nearly 10%, which indicated Grain for Green Project in this area made a good achievement. Besides, the residential area in Tongchuan almost doubled, which were mainly transformed from farmland, indicating the serious occupation of farmland resulted from the urban expansion.The land use / land cover mapping analysis showed that a larger area of farmland in the central west of the meridian Ridge mountains turned into bush land, cultivated land changed into forest land in forest and cultivated land over some hilly area, and that a large amount of arable land in Wangyi District, Yintai district and the southern Yaozhou changed to orchards; a small amount of land in the southern part of the city changed to residential areas, and that a larger area of the southwestern part turned into the bush forest land, the probable cause of which was that the district suffered from deforestation in the former period and reforestation in the latter period.The patches of land use types were 37694, 54584 and 59406 in the year of 1987, 1992 and 2002 respectively by landscape pattern analysis of land use/land cover. There was a rapid increase in the number of patches, fragmentation degree of land-use patches increased. plaque area and mean plaque area index showed the average land landscape matrix was farmland in 1987 and 1992, and forest land in 2002. The connectivity index of forest land, agricultural land and shrub forest were high, indicating that the connectivity of these three types of landscape were good, and formulated the dominant landscape types. Fractal dimension of land use in Tongchuan was high in general, mainly due to the influenced impacts of human planning by the complex topography, and the stability of farmland was low. In the landscape level, the overall landscape connectivity and dominant plaque decreased, and the index of Shannon diversity and evenness increased, and Tongchuan's landscape types tended to be complex, stable and diverse.Tongchuan's land use / land cover change was mainly affected by natural factors and human factors. In terms of natural factors, Tongchuan's distribution structure of land use types largely depended on its special geographical location and complex topography and landscape; as for human factors, population and economic were two major factors of land use change, in addition, policy was the main driving factors of short-term change of land use types. For example, the policy of returning farmland to forest made a significant reduction of cultivated land area and increase of vegetation coverage.