1982—2009年青藏高原草地覆盖度时空变化特征

利用GIMMS和SPOTVGT两种归一化植被指数(NDVI)数据对青藏高原地区1982—2009年期间草地覆盖的时空变化进行研究,结果如下:①青藏高原草地植被覆盖的年际变化存在着显著的空间差异。趋于升高的区域主要分布在西藏的北部和新疆的南部;趋于下降的地区主要分布在青海的柴达木盆地、祁连山、共和盆地、江河源地区及川西地区。②青藏高原草地覆盖度年际变化趋势分析表明,在90%的显著性检验水平上,降低和增加面积的比率为0.31,草地植被覆盖水平总体趋于升高态势。③以10 a为步长的分析表明:草地盖度呈现持续增加的区域主要分布在西藏北部;阿里地区草地盖度表现为先减少后增加;雅鲁藏布江流域草地盖度呈现先增加而后减少;而持续减少的区域主要分布在青海省以及川西地区,其中青海省分布最广;统计结果显示,高原大部分地区草地盖度具有升高的态势。

Temporal and Spatial Distribution of Grassland Coverage Change in Tibetan Plateau since 1982

Based on the remote sensing data such as NDVI data from GIMMS and SPOT VGT, the paper analyzed temporal and spatial distribution of grassland cover change from 1982 to 2009. The results showed that: 1) There was significant spatial difference in grassland coverage change. The area with grassland coverage increasing was mainly distributed in northern Tibet and southern Xinjiang; the area with grassland decreasing was mainly distributed in the headwaters of the Yangtze River, Yellow River, Lancang River, and Nujiang River, the Qaidam Basin and Gonghe Basin, Qilian Mountains and western Sichuan Province. 2) Statistics of grassland coverage inter-annual change showed that at significance test level of 90%, the rate of the area with coverage decreasing and increasing was 0.31, and the grassland coverage on Tibetan Plateau tends to be increased. 3) Analysis with ten years showed that: the grassland coverage with continuous increase was mainly distributed in northern Tibet; the grassland coverage in Ngari of Tibet decreased firstly and then increased; nevertheless, the Brahmaputra Valley increased firstly and then decreased; the area with continuous decreasing tendency was mainly distributed in Qinghai Province and western Sichuan Province; the statistics showed that most of the grassland coverage on Tibetan Plateau displayed an increasing tendency.