Sahelian Wooded Grassland
The chief woody species of these often-stunted woodlands 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 growing up to 8 m tall, but in some of the dryer areas it may grow no higher than 4 m. The density of these woodlands also varies from almost continuous canopy to open woodland in which each tree is separated by several crown diameters. 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).
Sahelian Panicum laetum-Echinochloa colona Grassland
Grassland dominated by Echinochloa colona and the endemic Panicum laetum (Poaceae) appears to be widespread in the western parts of this BioProvince. They appear very versitile being able to develop on sandy-silty, loamy and clayey soils and can tolerate water-saturation or repeated inundation during the wet season - they can also develop on dry non-inundated soils. Most of the associates are annual species whereas perennials are virtually absent. On the Sahelian peneplain in Burkina Faso, two sub-association or communities have been recognized – one characterized by Schoenofeldia gracilis and the other by Eragrostis pilosa. The former has its centre of occurrence on this peneplain and with good fodder value is often grazed. Other characteristic species include Aristida funiculata, A. mutabilis and Cleome scaposa, while the many other associates include Alysiocarpus ovalifolius, Dactyloctenium aegyptium, Spermacoce chaetocephala and the endemic Indigofera senegalensis (Fabaceae). The Eragrostis pilosa community appears to be confined to the Sahelian parts of the Burkina Faso and certain stands are regularly flooded during the rainy season. In such areas Schoenofeldia grassland is usually absent, but many associate species are common to both grasslands. Trees are rare but Acacia seyal, A. tortilis subsp. raddiana and Ziziphus mauritiana can be foundscattered throughout these grasslands.
Sahelian Semi-Desert Grassland
These semi-desert grasslands are typically dominated by Cenchrus biflorus but several species found in the wooded grasslands can also be found here. However, in northern Sahel close to the Sahara desert grasses such as Panicum turgidum and Stipagrostis pungens often become the main species.
Sahelian Deciduous Bushland
On some of the wetter rocky outcrops such as on the Darfur plateau and on the volcanic inselberg Jebel Gurgeil, a deciduous bushland or thicket dominated by Acacia mellifera and Commiphora africana can be found. Other associated species include Boscia senegalensis, Dichrostachys cinerea and Euphorbia candelabrum.
Sahelomontane Scrub Forest
On certain sheltered rocky slopes there are scrub forests dominated by Olea laperrinei (olive). The principal woody associates include Boscia angustifolia, Ficus populifolia, F. salicifolia, Maytenus senegalensis, Rhus vulgaris and Vangueria venosa.
Further information required.
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.
Monod, Th. 1986. Sahel Zone north of the equator. In: Ecosystems of the World 12B - Hot Deserts and Arid Shrubland, B. Eds. M. Evenari, I. Noy-Meir and D. W. Goodall. Elsevier.
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.