中文摘要：

利用1998-2010年SPOT-VGT NDVI影像对陕北地区植被的时空变化进行分析.结果表明：研究期间,陕北地区归一化植被指数（NDVI）的季相变化明显,月均最高值出现在8月、最小值出现在1月,月均值的变化幅度在0.14～0.46,NDVI月均值为0.28,其年均值总体呈上升趋势;在空间上,植被改善地区集中于陕北中南部,生态环境退化区域集中在长城以北风沙区;气温和降水是影响植被变化的重要气候因子,其与NDVI变化的相关系数分别为0.72和0.58;植被改善明显的区域主要位于坡度15°～25°的地区,反映出国家退耕还林还草工程对陕北地区生态环境的恢复和改善起到了巨大作用.

英文摘要：

By using 1998-2010 SPOT-VGT NDVI images,this paper analyzed the spatiotemporal variation of vegetation in northern Shaanxi.In 1998-2010,the NDVI in northern Shaanxi had an obvious seasonal variation.The average monthly NDVI was the minimum（0.14） in January and the maximum（0.46） in August,with a mean value of 0.28.The average annual NDVI presented an overall increasing trend,indicating that the vegetation in this area was in restoring.Spatially,the restoration of vegetation in this area was concentrated in central south part,and the degradation mainly occurred in the north of the Great Wall.Air temperature and precipitation were the important climate factors affecting the variation of vegetation,with the linear correlation coefficients to NDVI being 0.72 and 0.58,respectively.The regions with better restored vegetation were mainly on the slopes of 15°-25°,indicating that the Program of Conversion of Cropland to Forestland and Grassland had a favorable effect in the vegetation restoration in northern Shaanxi.