Included here is the Sahara - the largest desert in the world. In an east-west axis it stretches from the Libyan Desert to shores of the Atlantic Ocean, but the northern and southern boundaries are less well defined. In the north there is a gradual transition to Mediterranean vegetation, while in the south there is a transition to tropical vegetation.

Saharan Sandy Desert (Erg) Vegetation

Shifting sand is usually barren of vegetation but even where there is a degree of stability plants can only get established when their roots can penetrate into damper layers. The species composition of this demanding habitat varies. In the Western Sahara the main species are Stipagrostis pungens and endemic scrub Cornulacea monacantha (Chenopodiaceae). In the north several other scrub species can be found including Ephedra alata and the endemic Genista saharae (Fabaceae) and Retama retam (Fabaceae), while in central and southern areas Leptadenia pyrotechnica is one of the main scrub species. Apart from the near endemic Malcolmia aegytiaca (Brassicaceae) annual species are rarely found because the constantly moving sand hampers their establishment.

Saharan Gravel Desert (Reg) Vegetation

This type of habitat is fairly extensive especially in the hyper-arid zones, but unlike the more sandy areas, it is much less prone to wind erosion. Also in contrast to the sandy areas, the vegetation is almost entirely dominated by therophytes such as Asthenatherum (Danthonia) forskalii, Ifloga spicata, Neurada procumbens, Plantago ciliata, Polycarpaea repens (fragilis), the near endemic Fagonia glutinosa (Zygophyllaceae) and Monsonia nivea (Geraniaceae), and species of the endemic genus Ammodaucus (Apiaceae). The few perennial species include the endemic Haloxylon scoparium (Chenopodiaceae), which forms diffuse communities in northern Sahara.  Where deeper sand occurs communities characterized by Lasiurus hirsuta and the near endemic Zilla spinosa (Brassicaceae) can be found.

Saharan Stone Desert (Hamada) Vegetation

Stone pavements or hamadas are characteristic of plateaus where all products of weathering are removed by wind. Much of these areas are devoid of vegetation and plants can only grow in rock crevices and depressions where soils and moisture can accumulate. Despite this, species richness is comparatively high in these areas, and there is considerable variation in species composition. Among some of the more characteristic species are Astericus graveolens, Cymopogon schoenanthus, Enneapogon desvauxii, E. scaber, Fagonia latifolia, Farsetia aegyptiaca, Forsskalea tenacissima, Moricandia arvensis, Reseda villosa, and Salvia aegyptiaca. In the northwestern Sahara the endemic Fredolia (Anabasis) aretioides (Chenopodiaceae) is often the only perennial to occur over extensive plateau surfaces. This remarkable plant forms dense cushions up to 50 cm in diameter. Associated species include Limoniastrum feei and the almost leafless umbellifer Pitvranthos battandiferi.  In central Sahara hamada is almost absent except on the rocky flanks of high mountains where characteristic species include the near endemic perennials Aerva persica and Anabasis articulata (Amaranthaceae). These rocky habitats also provide habitat for various chasmophytic species such as Erodium glaucophyllum, Fagonia mollis and the near endemic Helianthemum kahiricum (Cistaceae) and Reaumuria hirtella (Tamaricaceae).

Saharan Pituranthos tortuosus-Gymnocarpus decandrum Desert Vegetation

Vegetation dominated by the two herbaceous species Pituranthos tortuosus and Gymnocarpus decandrum can be found, for example, on the Miocene and Quaternary plateaus of northern Marmarica. Other herbaceous species include the near endemic Zygophyllum album (Zygophyllaceae), but many of the associates are dwarf shrubs. Several other endemic or near endemic species commonly associated with this community include Anabasis articulata (Amaranthaceae), Erodium hirtum (Geraniaceae), Salsola tetrandra (Chenopodiaceae) and Trigonella stellata (Fabaceae). This vegetation also appears to spread in to the Mediterranean or sub-Mediterranean zones and has been recorded, for example, around Sidi Barrani in Egypt.

Saharan Stipagrostis plumosa Desert Grassland

Grassland dominated by tussocks of Stipagrostis plumosa can be found, for example, on the Eocene limestone in the Bahariyah, Sitra abd Farafra regions of Egypt. In the northern part of the Farfra oasis the vegetation typically grows in deep karstic holes filled with sand and known locally as flowerpot vegetation. Associated species mainly comprise herbaceous perennials and dwarf shrubs and may include Astragalus trigonus, A. vogelii, Calligonum comosum, Convolvulus pilosellifolius, Cotula cinerea, Fagonia arabica, Farsetia aegyptiaca, Launaea nudicaulis, Salsola baryosma, Stipagrostis zittelii, Tamarix passerinoides and the endemic or near endemic Anabasis articulata (Amaranthaceae), Cornulaca monacantha (Chenopodiaceae), Pituranthos tortuosus (Apiaceae), Suaeda vermiculata (Chenopodiaceae) and Zygophyllum album (Zygophyllaceae).

References

Bornkamm, R. & Kehl, H. 1990. The plant communities of the Western Desert of Egypt. Phytocoenologia, 19: 149-231.

Davis, P. H. 1953. The vegetation of the deserts near Cairo. Journal of Ecology, 41: 157-173. 

Houerou, H. N. Le. 1986. Northern Africa.  In: Ecosystems of the World 12B - Hot Deserts and Arid Shrubland, B. Eds. M. Evenari, I. Noy-Meir and D. W. Goodall. Elsevier.

McGinnies, W. G. et al. (eds). 1970. Deserts of the World. The University of Arizona Press.

Quezel, P. 1978. Analysis of the flora of the Mediterranean and Saharan Africa. Annals of the. Missouri Botanicl Garden, 65: 479-534.

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