| As the primary means of remote sensing technology, Based on the TM images of the study area in 1986 and 2003, Using the methods of a combination of supervised and unsupervised, We acquired two land use / land cover classification thematic maps of 1986 and 2003 and the LUCC maps from 1986 to 2003 in WuQi County, then analyzed two thematic maps and LUCC law in 17 years, the driving force on land-use changes and the benefits brought by returning farmland to forest(grass) in WuQi County, summed up the experience and practices of returning farmland to forest(grass) of WuQi County, raised some suggestions on sustainable development of returning farmland to forest(grass).The results show:(1) A series of image processing including tensile enhanced and false color fusion improved image recognition environment, enhanced the possibility of recognition of of message, increased the reliability of human-computer interaction interpretation, accuracy rate of interpretation reached 85%. The study used seven-band remote sensing images consisting of six original TM-band and NDVI. The method of combination of supervised and unsupervised is applicable to the Loess Plateau area. Not only can it greatly increase the speed of interpretation, but also ensure the accuracy of the classification.(2) The most important land use type in WuQi County in 1986 farmland and grassland, which respectively accounted for 29.90% and 44.95% in the whole county's land area of; But in 2003 is woodland and grassland. accounting for 36.76% and 45.30% respectively. Through analysis on LUCC and the transfer matrix, we found that there are 17 various great changes happened on land use types and space landscape patterns between 17 years. The main demonstrations are sharp decrease of forest and marked increase of farmland, and the significantly improvement on the quality of turf.(3) The main driving forces on LUCC of WuQi County are natural factors and human factors. The general law of LUCC in WuQi County is that the farmers disafforest massively in order to expand increase the farmland area in the 1980s and early 1990s, but in the late 1990s the Central Party raised the returning farmland to forests, then the acreage of farmland significantly reduced and the acreage of woodland increased dramatically. In recent years, the ecological environment of WuQi County has been greatly improved and achieved obvious ecological benefits, mainly due to the substantial increase in woodland and the significant improvement on grassland quality. Seen on the remote sensing images of 2003, the ecological environment is obviously better than surrounding areas.(4) Using computers technology to extract land use/land cover information from TM data is efficient and scientific, and can reflect the land-use trends of LUCC. But in the region of Loess Plateau ,there are so many mountains and gullies and broken terrain, which affect the accuracy of the classification. We suggest that DEM, gradient maps and subsidiary GIS should be introduced to eliminate the shadow of the terrain and extract the slope land by means of sloping grades, so that it can meet the demand of returning farmland to forest. |
