基于RS和GIS的退耕还林生态建设工程成效监测

Monitoring the effects of ecosystem restructuring project after returning farmland to forest based on RS and GIS

在GIS技术的支持下,利用SPOT VEGETATION数据从宏观上反映近年来植被覆盖所发生的变化;利用TM遥感影像解译土地利用状况、植被覆盖度,与DEM数据叠加分析计算坡耕地面积、土壤侵蚀强度,研究退耕还林前后的土地利用、植被覆盖度、坡耕地面积和土壤侵蚀强度的变化,较细致地揭示陕西省吴起县退耕还林生态建设工程的所取得的实效。结果表明,随着退耕还林工程的实施,吴起县域版图在遥感影像逐渐显现、越来越清晰,植被覆盖增加极为显著,高覆盖植被面积在逐年增加,低覆盖植被面积在逐年减少,植被恢复情况明显好于周围区域。与1997年相比,到2007年该县有75.15%耕地不再耕种,退出的耕地主要变为草地、林地和果园;林草覆盖率增加显著,由1997年的37.06%提高到2007年的80.60%;大于25°的坡耕地80%～90%实现了退耕;土壤侵蚀强度总体上降低,极强度、剧烈的高等级土壤侵蚀面积由1997年占国土总面积的42.52%下降到2007年的17.35%,但形势仍然严峻,需继续改善。

Based on GIS technique,vegetation coverage change was described in recent years by using SPOT VEGETATION,land use and vegetation coverage ratio were interpreted by using TM,furthermore,slope farmland and soil erosion intensity were analyzed by overlay method for understanding the effect of the project of returning farmland to forest or grassland（grain for green）.The territory profile of Wuqi County in northern Shaanxi Province was gradually clear-cut on SPOT VEGETATION images from 1999 to 2007.It is the green mark that the project makes.Vegetation was not only getting better and better in Wuqi county,but also getting better than the surroundings.Comparing with the status in 1997,75.15%of farmland was no longer cultivated,which was mainly returned to pasture,woodland or garden in 2007.The coverage ratio of woods and grass was greatly increased from 37.06%in 1997 to 80.60%in 2007.80%-90%of slope farmland with the gradient more than 25°was not cultivated.Soil erosion intensity was decreased as a whole,the areas of high and violent intensity soil erosion decreased from 42.52%in 1997 to 17.35%in 2007.However,its situation is still severe and it needs to be improved.further.