Based on the SPOT - VEGETATION NDVI data of year 2008 of the Heihe River basin, the oasis growing changes were quantitatively analyzed by use of mathematical statistical method, linear regression trend analysis and percentage change range analysis. The result showed that the growing stage of oasis vegetation was very significant in one year. The oasis vegetation trended to significantly raise on No. 1—18 ten-days (from January to June) No, fluctuated on 19—22 ten-days (from July to early August) and decreased on No. 23—36 ten-days (from mid August to December) . The rate of oasis vegetation growing change indicated apparent periodicity. From early January to late June the oasis vegetation grew better and better, but the fast increase of vegetation growing occurred from the middle of May to late May. The vegetation growth was getting worse from mid-August to late December, but the fast reducing of vegetation growth achieved mostly from late September to mid-October. The oasis vegetation growing change had obvious spatial differentiation . Yearly growing maximum change area was located in the main area of oasis. The best period of vegetation growing for the whole area varied from region to region in general, the area with the best period occurring on No. 22 ten-days was dominative, followed by the 20 ten-days and 18 ten-days, etc. Therefore, the remote sensing images in early August can be selected for the study of the whole basin oasis, and the remote sensing images in late June, mid-July or late September can be selected for the study of the local area.%利用2008年黑河流域SPOT-VEGETATION NDVI数据,采用数学统计、一元线性回归方法,对绿洲植被年内长势变化的过程、速度和幅度进行了定量分析;利用空间统计方法对各地区年内长势最佳期进行了分析.结果表明:(1)绿洲植被长势在一年中呈阶段性显著:第1-18旬(1-6月)明显上升,第19-22旬(7-8月上旬)波动,第23-36旬(8月中旬-12月)明显下降.(2)绿洲植被长势变化速度具有明显的时间差异性,第14-15旬的长势速度增加最快,第27-29旬的减少最快,而且增加和减少相当的区域略具空间一致性.(3)绿洲植被长势变化的幅度也具有明显的空间差异.绿洲核心区域年内长势变化最大,向外围依次递减.(4)各区域绿洲植被长势最佳期的出现具有差异性.总体而言以出现在第22旬(8月上旬)的区域占绝对优势,其次为第20旬和第18旬等.因此在选择遥感影像时针对全流域绿洲整体的研究可以选择8月上旬的影像,而针对局部区域可以选择6月下旬、7月中旬或9月下旬的影像.
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