The dynamics of grassland vegetation fractional coverage using time-series MODIS data in Gannan region of China

Based on the dimidiate pixel model and remote sensing technique, a new alpine grassland vegetation coverage analysis model on the basis of NDVI index was built and the fractional vegetation coverage was estimated in Gannan state in year 2000, 2002, 2004, 2006, 2008 and 2010 from MODIS data. Thus, the character of dynamic changes of the grass vegetation coverage was figured out with the varied 5 levels estimation results of vegetation fractional coverage and results of transfer matrixes based on GIS spacial analysis in the past 11 years. The results indicated that from year 2000 to 2010, the deterioration of grassland vegetation coverage in Gannan was general, and the degradation of level 1 the best stage of grass vegetation cover is higher absolutely. What´s more, the change of grassland cover indicated the trend of transform from high-stage (level 1, level 2) to low-stage (level 4, level 5) coverage. The research informed the fact further that the grassland vegetation in Gannan area is degrading more and more seriously, and it will be useful to the academic research and rangeland management by government.