塔里木河下游输水前后NDVI差异分析

运用统计方法分析塔里木河下游英苏、喀尔达依、阿拉干三断面输水前后归一化植被指数(NDVI)的差异大小并推测河畔植被对输水的响应程度。结果表明:随着输水进行,研究区NDVI与地下水埋深逐渐呈负相关趋势,NDVI增幅随地下水埋深减小逐渐增大;输水前后相同断面NDVI差异极显著,根据输水前后NDVI差值大小确定植被恢复速度为:英苏>喀尔达依>阿拉干;各断面NDVI在输水前没有差异,输水后断面间NDVI差异显著,根据差异大小确定恢复程度顺序为英苏>喀尔达依>阿拉干;以大西海子水库周边NDVI为参照,确定经7年8次生态输水英苏、喀尔达依、阿拉干三断面植被恢复度分别为20.2%、18.4%和8.4%。以上研究表明,研究区植被恢复仍然有限,坚持持续输水很有必要。

The Analysis on the NDVI Difference before and after Water Transfer to the Lower Reaches of Tarim River

Using statistical methods, this paper analyzed the NDVI differences before and after water transfer to Yinsu section, Kaerdayi section and Alagan section at Daxihaizi reservoir in the lower reaches of Tarim River as well as speculated the level of response of riparian vegetation at these sections to water transfer. The results showed that with the practice of water transfer, the study area’s NDVI and the groundwater level gradually presented negatively correlating trends, with the increase in groundwater level, the range of NDVI increase gradually increased; before and after water transfer NDVI difference varied significantly on the same sections, according to the degree of NDVI difference before and after water transfer the order of vegetation restoration speed is Yinsu> Kaerdayi> Alagan; no difference of NDVI among sections was observed before water transfer after at NDVI differs significantly among sections, according to the degree of vegetation restoration, the order is Yinsu> Kaerdayi> Alagan; taking NDVI of the neighboring Daxihaizi Reservoir as a reference, vegetation restoration rate of the three sections respectively is 20.2%,18.4% and 8.4%. The above study shows that, after seven years the ecological restoration of vegetation is still limited by water supply, hence, continuous water transfer is quite necessary.