Abstract: Grassland is the most important vegetation cover type in Gannan and Northwest Sichuan,accounting for about 43.91% of the study area. In order to find out the changes of grassland growth condition and its driving factors,based on MOD13A3 and the methods of Trend analysis,Coefficient of variation,Partial correlation analysis and Residual analysis,the changing trends and stabilities of growing period of grassland NDVI (Normalized Difference Vegetation Index) in the study area were analyzed,and the influence of meteorological factors and human activities on the change of grassland NDVI were also studied. The results showed:From 2000 to 2018,74.17% of the grassland areas in Gannan and Northwest Sichuan showed an upward trend,of which 17.15% passed the significant verification. The NDVI of grassland in the study area was high (mean value was 0.7096). NDVI of the whole region and all types of grassland showed a fluctuating upward trend in 19 years. The growth status was stable,only 6.08% of the grassland fluctuated significantly. Temperature and precipitation had positive effects on grassland NDVI,and the area of grassland NDVI positively correlating with temperature (70.19%) was larger than that of precipitation (62.63%). Human activities had negative impacts on grassland NDVI from 2000 to 2005,and positive impacts from 2006 to 2017.

Key words: Grassland, NDVI, Change trends, Driving factors, MOD13A3

摘要： 草地是甘南和川西北地区最主要的植被覆盖类型，约占研究区面积的43.91%。为探明该地区草地的生长状况变化及其驱动因素，基于MOD13A3数据，采用趋势分析、变异系数、偏相关分析和残差分析，对研究区草地归一化植被指数（Normalized Difference Vegetation Index，NDVI）时空动态变化和稳定性进行分析，并研究了气象因素和人类活动对草地NDVI变化的影响。结果表明：2000-2018年甘南和川西北地区草地生长期NDVI呈上升趋势的面积占比为74.17%，其中17.15%通过显著性验证；研究区草地NDVI整体较高（均值为0.7096），在19年间全区和各类型草地NDVI均呈波动上升趋势，生长状况稳定，仅有6.08%的草地波动幅度较大；温度和降水对研究区草地NDVI的变化主要呈正向驱动，且NDVI与温度呈正相关的面积（70.19%）大于降水（62.63%），人类活动在2000-2005年对草地NDVI呈负向影响，2006-2017年呈正向影响。

关键词: 草地, NDVI, 变化趋势, 驱动因素, MOD13A3