黄河源区植被变化趋势及其对气候变化的响应过程研究

摘要

The characteristics of vegetation and its response to climate change were explored using NOAA/ AVHRR (NOAA/Advanced Very High Resolution Radiometer) (1982-2001) and EOS/MODIS (Earth Observation System/Moderate Resolution Imaging Spectroradiometer) (2000 - 2008) NDVI (Normalized Difference Vegetation Index) products, monthly air temperature and precipitation of Maqu, Madoi, and Xinghai meteorology stations over the source region of the Yellow River. The results showed: The vegetation of Madoi region generally revealed a decreasing trend in the time and space scale; the vegetation of Maqu region, which is the source region of the up-stream Yellow River, revealed an increasing trend before 2000 and appeared to degenerate after that; The vegetation revealed a decreasing (increasing) trend before (after) 2000 in the north of the source region of the up-stream Yellow River. The NDVI appeared to decrease during 1982 - 1990 in the spatial scale, this occurred in the east region of the Ngoring Lake. The areas with decreasing trend of vegetation further enlarged during 1991 - 2000. During 2000 - 2008, an evident degeneration occurred in Maqu area, while the vegetation of Xinghai region generally increased. The responding relationship of the vegetation to climate change implied: The air temperature was the most sensitive factor to vegetation variation in the source region of the Yellow River, an exponential relationship existed between them, the NDVI had a little variation when the air temperature was lower than O.Ot), and the NDVI increased fast with the air temperature when the air temperature was greater than 5. 0 °C. Local precipitation had great contribution to the early growing of the vegetation, when the vegetation saturated and the NDVI reached maximum, local precipitation was not sensitive to vegetation variation anymore.%利用1982～2001年NOAA/AVHRR(美国大气海洋局卫星/甚高分辨率辐射计)NDVI(归一化植被指数)资料、2000～2008年EOS/MODIS(地球观测系统卫星/中等分辨率成像光谱仪)NDVI资料以及1982～2008年黄河源区的玛多、玛曲和兴海气象台站逐月气温和降水资料,分析了黄河源区玛多、玛曲和兴海地区卫星遥感植被指数的时空变化特征,探讨了全球变化背景下黄河源区植被对气候变化的响应过程.结果表明:黄河源区植被在时间和空间尺度上都呈现退化趋势.1982～1990年黄河源区植被退化主要发生黄河源区鄂陵湖以东区域；1991～2000年植被退化范围进一步扩大到源区北部兴海共和地区以及若尔盖草原；2000～2008年植被退化范围扩大至黄河上游主要水源涵养区的玛曲草原,但源区北部的兴海和共和地区却出现了植被增加的趋势.黄河源区植被对气候变化响应关系为:黄河源区水源涵养区植被对气温的响应最为敏感,气温低于0.0℃时,植被指数对气温的变化没有响应,当月平均气温大于5.0℃时,植被指数随气温的升高呈指数关系增长.局地降水对植被的影响非常复杂,在生长初期(4～6月)影响很大,但随着植被生长丰茂,植被指数达到高值而趋于饱和时,对局地降水的响应就会很小.