Zhang Hong-Bin, Yang Gui-Xia, Wu Wen-Bin, Li Gang, Chen Bao-Rui, Xin Xiao-Ping
Hulunber Grassland Ecosystem Observation and Research Station, Beijing 100081, China.
Ying Yong Sheng Tai Xue Bao. 2009 Nov;20(11):2743-9.
Time-series MODIS NDVI datasets from 2000 to 2008 were used to study the spatial change trend, fluctuation degree, and occurrence time of the annual NDVImax of four typical grassland types, i.e., lowland meadow, temperate steppe, temperate meadow steppe, and upland meadow, in Hulunber Grassland. In 2000-2008, the vegetation in Hulunber Grassland presented an obvious deterioration trend. The mean annual NDVImax of the four grassland types had a great fluctuation, especially in temperate steppe where the maximum change in the mean value of annual NDVImax approximated to 50%. As for the area change of different grade grasslands, the areas with NDVImax between 0.4 and 1 accounted for about 91% of the total grassland area, which suggested the good vegetation coverage in the Grassland. However, though the areas with NDVImax values in (0.4, 0.8) showed an increasing trend, the areas with NDVImax values in (0.2, 0.4) and (0.8, 1) decreased greatly in the study period. Overall, the deteriorating grassland took up about 66.25% of the total area, and the restoring grassland took the rest. There was about 62.85% of the grassland whose NDVImax occurred between the 193rd day and the 225th day in each year, indicating that this period was the most important vegetation growth season in Hulunber Grassland.
利用2000年至2008年的MODIS NDVI时间序列数据集，研究了呼伦贝尔草原低地草甸、温带草原、温带草甸草原和山地草甸4种典型草地类型年最大归一化植被指数（NDVImax）的空间变化趋势、波动程度及出现时间。2000 - 2008年，呼伦贝尔草原植被呈明显退化趋势。4种草地类型的年平均NDVImax波动较大，尤其是温带草原，其年平均NDVImax均值的最大变化接近50%。就不同等级草地的面积变化而言，NDVImax在0.4至1之间的区域约占草地总面积的91%，这表明该草原植被覆盖良好。然而，尽管NDVImax值在（0.4, 0.8）之间的区域呈增加趋势，但在研究期内，NDVImax值在（0.2, 0.4）和（0.8, 1）之间的区域大幅减少。总体而言，退化草地约占总面积的66.25%，恢复草地占其余部分。每年约62.85%的草地其NDVImax出现在第193天至第225天之间，这表明该时期是呼伦贝尔草原最重要的植被生长季节。
