中文摘要：

植被覆盖度是衡量草地植被生长状况的重要指标,对评价分析植被恢复状况具有重要意义。利用2001-2011年每年5-10月的Terra/MODIS月植被指数数据,结合2006-2009年甘南草地调查资料建立了甘南州草地生长季的植被覆盖度遥感反演模型,对比研究了不同草地植被覆盖度模型的精度,模拟分析了甘南州2001-2011年草地生长季期间不同等级的草地植被盖度时空分布特征及面积变化动态。研究结果表明,MODIS-EVI可以最大限度地减少环境因子的影响,在植被覆盖度高的地区使用更具优势,能很好地反映各类植被覆盖度的空间和时间差异性。MODIS增强型植被指数EVI的对数函数（y=33.658ln x＋112.65）可以较好地模拟甘南州草地植被盖度分布状况,总精度可达93.31%。近11年甘南州的草地植被盖度总体呈波动上升趋势,其中2001年、2003年和2008年草地植被覆盖明显偏低,2005年植被覆盖度最高,平均达78.43%。甘南州中西部及西南部地区的草地植被覆盖度较东部更好。甘南州近11年以来草地植被均以高和较高植被覆盖度为主,其余等级的草地植被覆盖度所占比例相对较小（6.98%）且稳定。总体上,甘南草地具有由高植被盖度向较高植被盖度转换的趋势。

英文摘要：

Vegetation coverage is an important indicator of grassland vegetation growth condition,and it has a crucial significance for evaluation and analysis of vegetation restoration.Using the Terra/MODIS product of MOD13A3 from May to October during 2001-2011,combined with ground observed data from 2006-2009,the inversion models of grassland vegetation coverage were established.Their precisions were compared and the characteristics of grassland vegetation coverage in the growing seasons of 2001-2011 were analyzed in Gannan Prefecture.The logarithmic function（y=33.658 ln x＋112.65）of MODIS-EVI（enhanced vegetation index）best simulated grassland vegetation coverage in Gannan pastoral areas with aprecision of 93.31%.MODISEVI had more advantages in high vegetation coverage regions,and accurately reflected the spatial and temporal differences of vegetation coverage while reducing the effect of environmental factors to the maximum extent.In the recent 11 years,grassland vegetation coverage in Gannan Prefecture has shown an increasing trend.The grassland vegetation coverage was highest（78.43%）in 2005,and the vegetation coverage of 2001,2003,and2008 were lower than those in other years.The vegetation coverage in mid-west and southwest areas was better than that in the eastern area.Grassland vegetation was dominated by high,then higher vegetation coverage levels,while the proportion of other grassland vegetation coverage levels were small（6.98%）and stable.Overall,grassland in Gannan Prefecture for the 11 years was characterized by transformation from a high vegetation coverage into an even higher vegetation coverage.