【摘要】 植被退化是全球环境变化研究的一个重点问题,植被状况是环境评估的重要指标。利用8km分辨率的NOAA-AVHRR/NDVI时间序列数据,对位于黄土高原的泾河流域1982~2003年植被特征及变化状况进行系统分析,并在此基础上评估降雨与流域植被的相互关系。研究主要利用了变化斜率法、主成分分析法和相关分析法,得到如下结论:过去22a来流域植被NDVI均值波幅和变化都很小,变化较显著的区域集中在流域上游和流域边缘的山区。变化斜率分析得出了类似的结论,气候变化以及人类活动导致的土地利用改变可能是影响在流域不同地区植被状态变化的主要原因。对NDVI时间序列的主成分分析发现PC1和PC2与植被覆盖和气候密切联系,PC3和PC4与流域汛期洪水有关,PC5和PC6体现了人类活动的影响。流域的NDVI与降雨显示了良好的相关性,降雨与NDVI相关性的阈值可能在550mm或更高。更多还原

【Abstract】 Vegetation degradation is one of the key subjects in the study of global environmental change,and the Normalized Difference Vegetation Index(NDVI)is generally recognized as a good indicator of terrestrial vegetation productivity and growth status.To evaluate the vegetation dynamic changes in the Jinghe watershed on Loess Plateau from 1982 to 2003,major methods of changing slope,principal component analysis and correlation analysis are employed with 8km resolution NOAA-NDVI time series data.Based on these analyses,the relationship between precipitation and NDVI is discussed.Results show that there is little change in both the amplitude and variety of NDVI during the past 22 years.Vegetation in the upper stream areas,typically the watershed marginal mountain areas,changes significantly.A trend analysis shows the similar finding on that vegetation dynamics in different areas tends to be induced by climate change and human land use transformation.A standardized principal components analysis indicates that the first two components,or PC1 and PC2,are closely related to vegetation and climate changes.While PC3 and PC4 are connected with floodwater in flooding seasons,PC5 and PC6 reflect the effects of human activities.Finally,the correlation analysis between NDVI and precipitation shows that they have a close positive relationship in this region.The rainfall sensitivity threshold reaches 550mm or even higher.更多还原