An Example of Sudan Zone Vegetation in Nigeria

Abstract

Ecological work was done in Sokoto Province, an area typical of Chevalier''s Sudan Zone with a mean annual rainfall of approx. 710 mm. and severe 7-mos. dry season. The vegetation is very open savanna woodland with fine- and broad-leaved trees in roughly equal proportions, with a fair number of thorny spp. The complex action of the soil mosaic and the 2 important biotic factors (grass fires and cattle) upon the vegetation is explained by considering first an "ideal" mesic community in which Anpgeissus leiocarpa, Combretum glutinosum and Strychnos spinosa are the co-dominant trees. Under the influence of more extreme edaphic and biotic factors the dominants segregate to form communities comparable to Braun''s association-segregates. Biotic factors vary in kind and intensity so transitional communities occur. Seral development occurs in each segregate but the segregates are not arranged in a single sere leading to one climax and must be regarded as equal in rank. The climax on high level sites appears to be deciduous woodland with a dense understory of erect and scandent shrubs and only occasional patches of grass; vegetation rather similar to this also occurs on rocky hills which are, to a large extent, free from cattle grazing and grass fires.