基于长时间序列NDVI资料的我国西北干旱区植被覆盖动态监测

植被是表征陆地生态系统的重要指标,气候变化对植被具有显著影响。虽然MODIS NDVI具有较高的精度,但时间序列长度有限,在年代际尺度的变化趋势研究中,仍然需要对AVHRR NDVI数据集进行时间序列的扩展和完善。本研究通过建立MODIS NDVI与AVHRR NDVI逐月线性回归模型,生成了长时间序列(1981-2013年)NDVI数据集;并以NDVI作为植被活动的指标,分析研究了近33年来西北干旱区的植被动态变化。结果表明:1)MODIS NDVI与LTDR NDVI数据具有较好的线性相关性,两者之间线性回归模型的决定系数均在0.7以上;2)近33年以来,西北干旱区的植被活动均呈现出增强的态势,其中稀疏植被区的植被活动在持续增强,植被整体状况在好转,而草地区的植被活动较为稳定,并未出现较大的变化;3)西北干旱区的气候呈现出暖湿化的特点,植被活动对气候变化较为敏感,NDVI与年平均温度和年降水量之间呈显著相关关系(P<0.05)。

Dynamic monitoring of vegetation coverage based on long time-series NDVI data sets in northwest arid region of China

Vegetation is an important indicator of terrestrial ecosystem, and is a sensitive indicator for climate change. Although MODIS NDVI has higher accuracy, the length of time-series is limited. Therefore, it is necessary to expand and improve the time-series AVHRR NDVI data sets. According to the linear regression models between MODIS NDVI and AVHRR NDVI for each month, we produced a long time-series NDVI data sets (1981-2013). Using the NDVI as an indicator of vegetation activity, this study analyzed vegetation dynamic changes in northwest arid region of China for recent 33 years. The results showed that: 1) MODIS NDVI and LTDR NDVI have linear correlations with a high determination coefficient (>0.8). 2) In recent 33 years, vegetation activity has been enhancing in whole study area, in which area of the sparse vegetation has been increasing continuously, and area of grassland vegetation has not been changed greatly. 3) The climate of this area has been becoming warmer and wetter than before. There are significant correlation among NDVI data, mean annual temperature and annual precipitation. Vegetation activity is sensitive for climate change, topography and human activities.