以黄上高原泾河流域为例,首先利用遥感植被指数和气候干燥度指数之间的回归模型,模拟出了潜在植被指数,在此基础上通过遥感监督分类方法得出泾河流域现生植被分布格局和潜在植被的分布格局,并利用转换矩阵方法得出了植被退化的空间态势.结果表明:泾河流域最主要的潜在植被类型是针阔叶疏林(32.44%)、阔叶落叶林(31.28%)和中牛灌丛(23.71%).与现生植被相比较,有25.08%的阔叶落叶林潜在分布区被开垦为农作物,13.32%退化为针阔叶疏林,13.04%退化为中生灌丛,14.22%变化为旱生灌丛,仅有25.90%的面积保持了阔叶落叶林植被;针阔叶疏林分布区主要退化为农作物(26.01%)、旱生灌丛(20.99%)、草甸(17.12%);中生灌丛主要退化为草甸(30.29%)和温带草原(43.21%).植被的退化以流域中部、南部的黄土残塬沟壑区退化最为严重,其次为流域北部的黄土丘陵区,而流域东部的子午岭山区和流域西部的六盘山区植被退化相对较轻.

JingheRiverBasin is chosen as a case to study vegetation degradation in Loess Plateau in this paper. Firstly, remote sensing based vegetation index (VI) and climatic aridity index are used to estimate potential vegetation index by regressionmodel approach. The spatialdistributions ofcurrentvegetation and potentialvegetation in JingheRiverBasin are then obtained according to supervised classification of NDVI remote images and potential vegetation index. The status or severity of vegetation degradation is analyzed bymeans of the transferpossibility between vegetation types. The result shows that themain potential vegetation types of the Jinghe River Basin are broadleaved and coniferousmixed sparse forest(32.44% ), broadleaved deciduous forest(31.28% ) and shrub(23.71% ).It is found that25.08% and13.32% of the broad leaves forestpotential regionwere converted to cultivated land and broadleaved and coniferous mixed sparse fores,t while13.04% and14.22% changed to shrub and aridity shrub with only 25.09% potential region remained broad leaves fores.t Potentialregion of the broadleaved and coniferousmixed spare forestchanged to cropland(26.01% ), aridity shrub(20.99% ) and meadow (17.12% ) whereas potential region for shrub was dominant by meadow (30.29% ) and grassland (43.21% ).Vegetation degradation ismost serious in loess gully region, followed by loess hilly region in northern basinwhereas vegetation degradation inmountain region ofZiwuling in eastern basin and Liupanshan inwestern basin are relative sligh.t