SATELLITE-BASED HERBACEOUS BIOMASS ESTIMATES IN THE PASTORAL ZONE OF NIGER

Pastoralists in the Sahel of northern Africa are entirely dependent on their livestock, which graze on the annual vegetation produced during a relatively short summer rainfall season. The satellite-based normal ized difference vegetation index, calibrated with ground-truth samplin g of herbaceous biomass throughout the pastoral zone of Niger, was use d to estimate standing biomass for the entire Nigerien pastoral zone, Data were obtained and analyzed during a 5-year period from 1986 throu gh 1990. Techniques developed allow officials with the Government of N iger to estimate herbage available to support animal populations throu ghout the pastoral zone at the end of the growing season and plan graz ing strategies for the impending dry season. End-of-season herbage sta nding crop varied from less than 200 kg ha(-1) to nearly 1,700 kg ha(- 1) with locations and years. Strong biomass gradients were evident fro m mesic conditions in the southern pastoral zone to xeric conditions i n the north.