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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.
The temporal and spatial variations of vegetation in northern Shaanxi were analyzed using the SPOT-VGT NDVI images from 1998 to 2010. The results showed that the seasonal variation of NDVI in northern Shaanxi Province was significant during the study period, with the highest monthly mean value In August, the minimum value appeared in January, the monthly average change ranged from 0.14 to 0.46, and the monthly average NDVI value was 0.28. The annual mean value of the NDVI showed an overall upward trend. In spatially, the areas with improved vegetation were concentrated in central-southern Shaanxi and the ecological environment The degenerated areas are concentrated in the sandy area north of the Great Wall. Temperature and precipitation are the important climatic factors that affect the vegetation change, and the correlation coefficients with NDVI are 0.72 and 0.58, respectively. The areas with obvious vegetation improvement are mainly located in the areas of 15 ° ~ 25 ° slope , Reflecting that the project of returning farmland to forests and grasslands has played a significant role in the restoration and improvement of ecological environment in northern Shaanxi.