Remote sensing of the seasonal variability of vegetation in a semi-arid environment

This case study assesses the use of satellite data to monitor the vegetatio n cover in two types of semi-arid environments - sand dune and rocky - loca ted in the Negev Desert of Israel. In this study, satellite images acquired by NOAA/AVHRR over a time period of 2 years were analysed. The phenologica l spectral characteristics of vegetation in the two environments are very s imilar. Comparison between the AVHRR-derived NDVI (Normalized Difference Ve getation Index) values and rainfall data shows dependence of the NDVI value s on the sum of the amount of rainfall during the concurrent month and the two previous months. Field observations show that the vegetation components in the two semi-arid environments respond to rainfall with a time lag. The satellite-observed peak of NDVI occurs at the same time as the peak of the delayed response of annuals and perennials to rainfall. (C) 2000 Academic Press.