The Study On Land Use/Land Cover Change In Agriculture And Pasturage Interlaced Zone Of Northern Shaanxi

Study on the land use/land cover change by using the remote sensing images is the key field and basic method of global change research. We chose the Hengshan County which in the agriculture and pasturage interlaced zone of northern shaanxi as a study area, and then used the hierarchical classification method to extract land use/land cover information from TM images of the Hengshan County, obtained the thematic maps of 1986 and 2003. Through analyzed the law of land use/land cover change, the main results we obtained as follows:(1) Based on the spectral characteristics of different land cover type by TM image, chose different characteristic parameter to extract the information layer by Layer. First extracting water area by TM5/TM3, and then divided the other region into vegetation region and non-vegetation region by NDVI. In non-vegetation region, extracted town land by NDBI and NDVI, then separated sandy land and waste grassland by TM5. We divided the vegetation region into three classes by NDVI: grassland, dry land and shrub forest, irrigated land and forest land, then separated dry land and shrub forest in class 2 by TM4, irrigated land and shrub forest in class 3 by the difference of TM5-TM4. The result of accuracy evaluation showed that the overall classification accuracy is 86.8%, the Kappa coefficient is 0.8506 and they satisfied the classification accuracy Standard.(2) The most important land use type of Hengshan County in 1986 were dry land and grassland, which accounted for 36.62% and 18.87% respectively in the whole county's land area, but in 2003 were shrub forest and grassland, accounting for 32.91% and 22.46% respectively.(3) The overall situation of land use/land cover change in Hengshan County from 1986 to 2003 was as follows: The area of irrigated land, forest land, shrub forest, grassland and waste grassland were increased, and the largest increase was shrub forest. The area of dry land, water area and sandy land were decreased, and the largest decrease was dry land. The annual gradient of land use type was 1.71%. The town land, shrub forest, irrigated land and forest land were increased by 14.12%, 6.99%, 4.14% and 1.80% respectively every year, and sandy land, dry land and water area were decreased by 3.85%, 2.56% and 2.49% respectively.(4) The main transformation characteristics of land use types in Hengshan County from 1986 to 2003 were: dry land transformed to woodland and grassland, the transformation area were 51237.09hm2 and 32802.57hm2 respectively, grassland transformed to shrub forest, the transformation area was 34209.13hm2, water area transformed to irrigated land, the transformation area was 1524.57hm2, sandy land transformed to shrub forest and grassland, the transformation area were 6548.64hm2 and 15455.34hm2 respectively. The interior of unutilized land changed strongly, the area of sandy land transformed to waste grassland was 16747.31hm2.