AVHRR MONITORING OF SAVANNA PRIMARY PRODUCTION IN SENEGAL, WEST AFRICA - 1987-1988

NOAA Advanced Very High Resolution Radiometer (AVHRR) data were used to produce savanna primary productivity maps for Senegal north of the Gambia in 1987 and 1988. Measurements of herbaceous production, and also the sum of herbaceous and tree-leaf production, were regressed on temporal integrals of normalized difference vegetation indices (NDVI). Ground data were collected from 17 sites in the north Ferlo region in the Sahelian bioclimatic zone in both years and from an additional 10 sites located further south in the north Sudanian zone in 1988. The addition of tree-leaf production measurements to herb production increased the proportion of the variance of the NDVI integrals, which was explained by 16.8 per cent in 1987 and 6.7 per cent in 1988. The parameters of the regression obtained for 1987 compared favourably with Prince's synthesis of results from the Sahelian zones of Senegal, Mali and Niger. The regression obtained for 1988, however, was markedly different. Atmospheric water vapour, haze and cloud cover appear to have been higher in 1988, suppressing the integrated NDVI values across most of the study area. This effect increased in a southerly direction, possibly owing to the higher humidity and rainfall normally experienced in the Sudanian zone compared to the Sahelian zone.