用MODIS NDVI数据2000—2015年的归一化植被指数产品,运用变异系数、Theil-Sen median趋势分析耦合Mann-Kendall检验和Hurst指数法,探讨了中国西北干旱区植被覆盖的时空变化特征及未来趋势的预测。研究表明:1)2000—2015年全区植被覆盖的空间异质性较强,有植被覆盖的区域占总面积的35.59%,无植被覆盖的区域占64.41%。受降水的影响,植被覆盖整体呈东南高西北低、山区高平原低的特点;受河流和人工灌溉的影响,绿洲区水热组合条件好,其植被覆盖高于荒漠区。2)近16年全区植被覆盖波动变化不明显,各亚区的波动普遍较低,变异系数小于0.10的比例均超过总面积的1/2。3)16年间全区植被覆盖总体有增长趋势,变化率为0.006/10a。基于像元尺度的分析也表明全区植被覆盖以增长趋势为主,各亚区中河西走廊的增长面积最多,北疆的增长面积最少,均超过1/2。4)全区NDVI的Hurst指数均值为0.73,Hurst指数大于0.5的范围所占比例为86.25%,未来全区植被覆盖的变化趋势以持续性增加为主,其中13.46%区域的未来趋势无法确定。各亚区呈不同程度的增加趋势,河西走廊的增加趋势最明显,北疆的增加趋势相对较弱。

Based on the MODIS NDVI data of the normalized difference vegetation index products obtained between 2000 and 2015,Variable coefficient,Theil-Sen median trend analysis,Mann-Kendall test method and Hurst index method were utilized for research on the temporal-spatial dynamic change characteristics of vegetation coverage in the arid region of Northwest China and the future trends. The results showed:1)the vegetation coverage in the entire region has a strong spatial heterogeneity,the area of vegetation and bare fallow accounts for 35.59% and 64.41% of the total area,respectively. Affected by precipitation,higher value area of NDVI is mainly in the mountains and southeastern region which have a rich rainfall,the low value areas of NDVI are concentrated on plains and northwestern region which have a poor rainfall;Influenced by rivers and irrigation,the vegetation coverage of desert is lower than the oasis which has the better hydrothermal conditions. 2)the variation degree of the entire regional vegetation coverage in the recent 16 years was not obvious. The fluctuation in each subregion is slight,and the proportion of region where the variation degree is less than 0.10 is as high as 1/2. 3)the entire regional vegetation coverage in the recent 16 years shows fluctuation changes which have a increase trend,the change rate is 0.006/10a. The analysis based on the pixel scale also shows a increase trend,the area of increase trend in Hexi Corridor is the largest and in Northern Xinjiang is the least. 4)Hurst index average of the entire regional NDVI is 0.73. The scope of Hurst index greater than 0.5 accounts for 86.25%. The change trend of the entire regional vegetation coverage in the future is mainly in persistent increase. Among them,13.46% area change trend cannot be determined. The change trend in the future of the increase degree in each subregion is different,the increase trend in Hexi Corridor is the most obvious and in Northern Xinjiang is the least.