The Sahel is a belt of semi-arid land that runs the length of the Sahara Desert’s southern margin extending in a narrow zone some 400 km wide from the Red Sea coast of Sudan to the Atlantic coasts of Mauritainia and Senegal.

These are woodland savannas in which tree density ranges from almost continuous canopy to open savanna in which each tree is separated by several crown diameters. The chief woody species, which are often stunted, include Acacia tortilis, A. laeta, Commiphora africana, Balanites aegyptiaca, Boscia senegalensis, Maerua crassifolia and Leptadenia pyrotechnica.  Acacia tortilis is by far the most important of these often reaching heights of up to 8 m tall but in some of the dryer areas it may grow no higher than about 4 m. The associated grass sward, which reaches heights of 60 cm, mostly consists of annual species such as Aristida stipoides, Cenchrus biflora, Schoenefeldia gracilis and Tragus racemosus. Perennial grasses are much more localized but Andropogon mosus sometimes forms pure stands. Other species associated with this habitat include the near endemic Piliostigma reticulata (Fabaceae).

References

Brenan, J. P. M. 1978. Some aspects of the phytogeography of tropical Africa. Annals of the Missouri Botanical Garden, 65: 437-474.

Cook, C. D. K. 1968. The vegetation of the Kainji Reservoir site in Northern Nigeria, Vegetatio, 15: 225-243.

Kassas, M. 1957. On the ecology of the Red Sea coastal land. Journal of Ecology, 45: 187-203.

Müller, J. V. 2008. Grassland communities on the Sahelian peneplain in Burkina Faso. Feddes Repertorium, 119: 42-62.

White, F. 1983. The Vegetation of Africa. UNESCO.