A COMPARISON OF THE VEGETATION RESPONSE TO RAINFALL IN THE SAHEL AND EAST-AFRICA, USING NORMALIZED DIFFERENCE VEGETATION INDEX FROM NOAA AVHRR
A COMPARISON OF THE VEGETATION RESPONSE TO RAINFALL IN THE SAHEL AND EAST-AFRICA, USING NORMALIZED DIFFERENCE VEGETATION INDEX FROM NOAA AVHRR
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DOI：
10.1007/bf00138369
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发表时间：
1990-12-01
期刊：
影响因子：
4.8
通讯作者：
MALO, AR
中科院分区：
文献类型：
--
作者：
NICHOLSON, SE;DAVENPORT, ML;MALO, AR
本文介绍了东非和萨赫勒地区降雨量与归一化植被指数 (NDVI) 之间关系的研究结果。对 1982 年至 1985 年的月度数据进行了分析。我们使用 White (1983) 描述的主要结构，按植被类型评估了 NDVI-降雨关系。在文章中，强调了两个研究区域植被生长对降雨的差异响应的比较。我们的研究最重要的结论如下：（1）年综合NDVI的空间格局密切反映了年平均降雨量。 (2)年平均降雨量在200～1200毫米左右的地区，降雨量变化与NDVI在季节和年际时间尺度上存在良好的相关性。 (3) 在大多数情况下，NDVI 与当前月份和前两个月的降雨总量相关性最好；萨赫勒地区的相关性比东非更好。 (4)东非NDVI与降雨量的比率远高于萨赫勒地区。 (5) 萨赫勒地区年平均综合 NDVI 与年平均降雨量呈线性相关。在东非，这种关系近似于对数线性；在降雨量高于某个阈值时，NDVI 值会趋于平稳，并且随降雨量变化极小。对最后一个结论提出了两种可能的解释：超过这个阈值，降雨量不再是植被生长的限制因素和/或 NDVI 不是植被生长的良好指标。后者很可能是因为 NDVI 直接反映光合作用活动，并且随着达到高冠层密度而成为生物量（即生长）的不良指标。东非的 NDVI-降雨量关系与 Sellers (1985) 和 Asrar 等人证明的 NDVI 和叶面积指数之间的关系非常相似。 （1984）。
This article presents the results of a study of the relationship between rainfall and Normalized Difference Vegetation Index (NDVI) in East Africa and the Sahel. Monthly data for the years 1982 to 1985 have been analyzed. We have evaluated NDVI-rainfall relationships by vegetation type, using the major formations described by White (1983). In the article, a comparison of the differential response of vegetation growth to rainfall in the two study regions is emphasized. The most important conclusions of our research are as follows: (1) The spatial patterns of annually-integrated NDVI closely reflect mean annual rainfall. (2) There is a good relationship between rainfall variations and NDVI on seasonal and interannual time scales for areas where mean annual rainfall ranges from approximately 200 to 1200 mm. (3) In most cases, NDVI is best correlated with the rainfall total for the concurrent plus two antecedent months; the correlation is better in the Sahel than in East Africa. (4) The ratios of NDVI to rainfall are considerably higher in East Africa than in the Sahel. (5) Mean annually-integrated NDVI is linearly related to mean annual rainfall in the Sahel. In East Africa the relationship is approximately log-linear; above some threshold value of rainfall, NDVI values level off and vary minimally with rainfall. Two possible explanations of this last conclusion are suggested: above this threshold, rainfall is no longer the limiting factor in vegetation growth and/or NDVI is not a good indicator of vegetation growth. The latter is a likely possibility since NDVI directly reflects photosynthetic activity and becomes a poor indicator of biomass (i.e., growth) as high canopy densities are reached. The NDVI-rainfall relationship for East Africa is markedly similar to the relationship between NDVI and Leaf Area Index demonstrated by Sellers (1985) and Asrar et al. (1984).