Seasonal fluctuations in foliation of some trees and shrubs in the Sahel. Consequences for the assessment of fodder resources

Abstract

The seasonality of the foliation of 28 Sahelian trees and shrubs was studied in order to determine the seasonal availabilities in browse feed and their interannual variations. Standard branchlets of each species were sampled each month, from 1979 to 1992, at sites located along the Sahelian bioclimatic gradient in Mali. Five phenological types were identified from the seasonality of their foliage. Three of them were deciduous plants characterized by the duration of their foliation, and the two others were evergreen plants characterized by the season of foliage renewal. Inter-site and interannual differences in foliar density were quantified and their ecology studied by analysis of variance. The seasonal maximum foliage density was shown to depend mainly on soil moisture accumulated in the previous year. To conclude, it is suggested that foliage seasonality and interannual fluctuations should be included in the assessment of feed resources offered by browses and, more generally, in any attempt to quantify the role of woody plants in the Sahelian ecosystem.