基于RS/GIS的中尺度地区退耕变化及其坡度分异研究

应用遥感和地理信息系统相结合的办法，提取了黄土高原中尺度地区（延安示范区）2000—2003年间各土地利用数字图，进行动态监测，并与坡度图结合，对其土地利用及退耕合理性进行分析。结果表明，3a前后，坡耕地、疏林地、造林地、草地类间发生了用地调整。坡耕地面积大幅度减少，减少幅度为35.9%；园地增加比重达28.1%；造林地面积增大到了3a前的2.03倍；研究区生态环境质量得到改善。研究区坡度分异表明，沟沿线上以8~15°、15~25°的缓坡和稍陡坡地居多，沟沿线下以>35°的陡沟坡和<3°的平地比例居多。2003年的各利用类型中，70.73%的基本农田面积<15°，63.61%的园地集中在<25°，78.18%的乔灌林地分布在>25°，草地则集中在>25°的陡坡地，比重达75.49%，在地形上的分异比较合理。但是2000年坡耕地仍有64%未退耕，32.75%的面积大于侵蚀临界角25°，形成水土流失隐患。依据地形自然分异判定其合理性，加强科学规划和科技支撑是未来退耕中必需要解决的首要关键问题。

Study of Land-use / Farming land Converting Change and their slope gradient differentiation on the middle scale research site using emote Sensing Data

Based on the RS and GIS methods, the authors extracted the land use / land cover information from aero photograph in November 2000, and got the 2003 data from field survey. We also got the slope degree data from measuring the topography map and combined with the land use /land cover data to dynamically monitor and analyze the status of land use and its suitability. The results showed that:(1) The land use changed greatly in the research site during 2000-2003. The slope farm land decreased by 35.9%, the orchard land increased by 28.1%, and the afforested land increased by 103%. The quality of ecology in the research site was improved largely. (2) In the research site, which stands for the typical loess hilly gully region, more than 50% of land was eroded. Over gully ridge distributed the most land from 8-15?and 15-25?. While the most land under gully ridge belong to <3? and >35?. (3) In 2003, the different land use types focused the different slope degree scope. 70.73％ of terrain land is less than 15?, 63.61% of orchard land less than 25?, 78.18% of forest and shrub land great than 25?, 75.49% of grass land is in the eroded gully region, where is greater than 25?. From the angle of soil and water conservation and natural suitability of land, the differentiation of land use/land cover is reasonable generally. (4) The research site still has slope farmland of 46.53km2 in 2003, which occupy 64% of 2000. 32.75% is great than 25?, the critical angle of erosion. Due to lacking the protection, erosion on this part of land happened very easily and increasingly, which is the big hidden trouble of soil and water loss.In the future, the key measure of converting the slope farm land and improving the ecology environment efficiently, is to justify the reasonability according to the slope degree differentiation, strengthen the land use planning, and get support from science and technolpogy.