基于遥感的塔里木河下游地下水埋深对植被覆盖的影响

Influence of Groundwater Depth on Vegetation Coverage in the Lower Reaches of Tarim River Based on Remote Sensing

塔里木河下游绿洲气候干旱,降水稀少、蒸发强烈,生态环境脆弱。地下水埋深对区域植被覆盖度具有重要影响。基于Landsat影像数据,利用归一化植被指数(NDVI)、像元二分模型、影像差值计算等方法分析了塔里木河下游植被覆盖度的空间格局和变化规律;并结合该地区同期的地下水数据,通过计算相关系数分析了地下水埋深对植被覆盖度的影响。结果表明:塔里木河下游绿洲植被总体以塔里木河下游段为轴线,从高植被覆盖到低植被覆盖向外分布;塔里木河下游绿洲植被覆盖空间变化存在区域性差异,过去17年塔里木河下游绿洲植被覆盖面积和植被覆盖度均呈上升趋势,2017年植被覆盖总面积比2001年增加了884.0 km^(2),增幅为13.3%;2001—2017年塔里木河下游绿洲整体地下水位上升,适宜植被生长的最佳地下水埋深为2~4 m,埋深为4~6 m对植被覆盖度具有改善作用,埋深大于6 m则对植被覆盖度影响不大。

The oasis in the lower reaches of Tarim River has arid climate,scarce precipitation,strong evaporation and fragile ecological environment.The groundwater depth has an important impact on the regional vegetation coverage.Based on Landsat image data,we used normalized vegetation index(NDVI),pixel binary model,image difference calculation and other methods to analyze the spatial pattern and vegetation coverage changes in the lower reaches of Tarim River.And then,combining with the groundwater data from the same period in the region,we analyzed the influence of groundwater depth on vegetation coverage by calculating the correlation coefficient.The results show that(1)the distribution of oasis vegetation in the lower reaches of Tarim River is from high vegetation to low vegetation.(2)There are regional differences in the spatial change of oasis vegetation coverage in the lower reaches of Tarim River.In the past 17 years,the area and vegetation coverage of oasis in the lower reaches of Tarim River showed an increasing trend.Compared with 2001,the total vegetation coverage area in 2017 increased by 884.0 km^(2),with an increase of 13.3%.(3)The groundwater level of oasis in the lower reaches of Tarim River has risen from 2011 to 2017.The optimum groundwater depth for vegetation growth is 2~4 m.When the groundwater depth is 4~6 m,it can improve the vegetation coverage.When the groundwater depth is greater than 6 m,it has little influence on the vegetation coverage.