Vegetation Coverage Estimation over Tibetan Plateau Using MODIS Data

The relationships between NDVI and SAVI from MODIS(Terra)imagery on September 13and 14,2004,and vegetation coverage derived from field measurements investigated at same time with MODIS data in central Tibetan Plateau are analyzed.Another hand,after selected typical grassland vegetation re-gion in central Tibetan Plateau and whole Tibetan Plateau as two study areas,the accuracy of Carlson and Ripley algorithm of vegetation coverage is validated using field measurements in this paper.The main con-clusions are as follows.(1)The relationship coefficient between NDVI and vegetation coverage from field investigation is 0.95(R2=0.90),between SAVI and vegetation coverage reaches 0.94(R2=0.89).(2)There is high relationship between vegetation coverage based on the field measurements and esti-mation from Carlson and Ripley algorithm,coefficients are greater than 0.94;it was found that Carlson and Ripley algorithm is suitable for the middle grassland vegetation coverage.(3)Overall,the vegetation coverage over Tibetan Plateau is low;the area of vegetation coverage lower than 20%covered more than 50%of total area.The vegetation coverage between 1%～10%is the largest area(35.36%)and it mainly distributed over northwestern area and south of Mountain Kunlun in Tibetan Plateau.The area of 100%of vegetation coverage is 122 538.88km2 and it covered 10.72%of the total are-a,which distributed in southeastern Tibetan Plateau where dominated by forest vegetation.The distribu-tion pattern of vegetation coverage over Tibetan Plateau decreases from southeast to northwest in Tibetan Plateau.