毁林开荒过程是一种林地变为耕地的土地利用变化过程,可以通过遥感和GIS技术对这一过程进行监测。本文通过覆盖全国的TM影像数据,对20世纪90年代林地转为耕地的面积及其空间分布进行分析,从而对全国毁林开荒过程进行遥感监测。结果表明,该时期有17630km²的林地被开垦为耕地。不同面积等级的开垦过程在不同流域分布也不同:面积小于10hm²和介于10～100hm²的被开垦林地较广泛地分布于各大流域;而面积介于100～1000hm²的被开垦林地主要分布于松辽流域、黑龙江流域和东北东部流域、长江流域、珠江流域和云南省所在流域;大于1000hm²的被开垦林地则几乎全部分布于松辽流域、黑龙江流域和东北东部流域。坡度大于3°的毁林开荒地面积占总面积的295%;对土壤侵蚀背景的分析表明,土壤侵蚀强度以微度和轻度为主

Land reclamation at the expense of deforestation has causing serious environmental problems in China As a process of land use changes, the lost forest can be identified based on remote sensing technique The nationally covered Landsat TM images in 2000 and the 1980s are spatially corrected and manual classification is carried out The forest land converting to cropland from the 1980s to 2000 are investigated with GIS method The results show that altogether 17630 km² of forest land were converted to cropland during this period of time Among them, the area of densely covered forest is 10467 km² ,accounting for 59 4% of the total deforested area; the sparsely covered forest is 3142 km² ,accounting for 17 8%; the shrubby land area is 3560 km² , accounting for 20 2%; and the other types of forest area is 460 km² With the aid of 1∶100000 watershed map, the distribution of reclaimed deforested land in each main watershed is analyzed The results show that the reclamation mostly happens in Northeast China, being 71 1% of the total lost forest For the three main watersheds in Northeast China, the Songhuajiang Liaohe Watershed (the southern part of Northeast China) occupies 9107 7 km² , accounting for 52 4% of the total reclaimed deforestation area; the Heilongjiang Watershed (the northern part of Northeast China) and the watershed in eastern part of Northeast China occupy 1883 4 km² and 1351 3 km² of lost forest respectively The percentages of the lost forest in watersheds of Yangtse River, the northern part of North China and southeastern part of Northeast China are 3 1%, 3 4% and 3 6% respectively Watersheds of Huaihe and Zhujiang rivers, and the coastal area of Southeast China have more than 1% of reclaimed forest Other watersheds in China have less than 1% of reclaimed forest each With DEM data, the reclaimed forests with different slopes are dealt with in the paper The forest with a slope greater than 3° covers 5205 km² , taking up 29 5% of the total lost forest in China Overlapping analysis of the data of soil erosion intensity derived from remote sensing and the spatial distribution of deforestation in China is carried out The deforestation process led to the increase in the slope cropland area and sharp increase in the value of C factor in soil erosion model of RUSLE , both contributing to the aggravation of soil erosion in China