Caractérisation des ressources herbagères de l’enclave pastorale de Dadaria (Mainé-Soroa, Diffa) au Niger

This study aimed at characterizing the pastures of the pastoral enclave of Dadaria in terms of floristic diversity, pastoral value, productivity and carrying capacity. A plant inventory of the herbaceous vegetation was carried out on 53 plots from south to north. The results showed that the site contained 93 species, including 83 herbaceous species in 30 families and 63 genera. The flora was largely dominated by the Poaceae, and the most abundant and dominant biological type was that of the therophytes. The forage spectrum showed that the grazing value varied from 60% in group 1 (G1) to 70% in G3. The overall grassland quality index followed the same trend and fluctuated from 58% in G1 to 64% in G4. Five species (Spermacoce chaetocephala DC. Hepper, Alysicarpus ovalifolius Schum. & Thonn, Zornia glochidiata Reich. ex DC, Digitaria argillacea (Hitch. & Chase) Fern, and C. prieurii Kunth.) accounted for 75% of species-specific contributions. Overall, the herbaceous phytomass production was estimated at 3.4 tons of dry matter (DM) per hectare and varied by group. Spectrum analysis of forage production by herbaceous species indicated that S. chaetocephala (68 kg DM/ha), A. ovalifolius (20 kg DM/ha), C. prieurii (15 kg DM/ha) and Z. glochidiata (9 kg DM/ha) were the most productive. S. chaetocephala contributed the most and was the most productive but with a low pastoral value. The gradual disappearance of annual grasses (Cenchrus biflorus Roxb. and the Aristideae tribe), which provide very good dry standing forage for livestock during the dry season, in benefit of fodder legumes that disappear just after the rainy season leaving the enclave bare, constitutes a regressive dynamic of the herbaceous cover of this Sahelian pastoral ecosystem.