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.

Saharomontane Vegetation

Distinctive montane vegetation is mainly confined to the higher mountains such as Ahaggar, Tassil’ n’ Ajjer and Tibesti, which receive more rain than the surrounding lowlands. The main types of vegetation are montane wadis communities, montane grassland and dwarf shrubland. On Ahaggar the most characteristic tree of the wadis is Olea laperrinei, often found in association with the two shrubs Pictacia atlantica and the near endemic Rhus tripartite (Anacardiaceae). However, this type of vegetation is completely absent from Tibesti, but in the moister wadis of both Ahaggar and Tibesti, communities characterized by Nerium oleander and the endemic Myrtus nivellei (Myrtaceae) occur. Tibesti, on the other hand, has a much richer woody flora than Ahaggar, especially on its wetter south and southwest slopes. The most characteristic species here is the near endemic Acacia seyal (Fabaceae), while associated species include Acacia albida, Boscia salicifolia, Cordia sinensis, Ficus ingens, Grewia tenax, Securinega virosa, the near endemic Balanites aegyptiaca (Zygophyllaceae) and Maytenus senegalensis (Celastraceae) and the endemic Ficus teloukat (Moraceae). Not present though is the remarkable endemic tree Cupressus dupreziana (Cupressaceae), which reaches heights of 20 m and may have a bole measuring 3 m in diameter. This species is now confined to a few rocky valleys in Tassili n’ Ajjer. The montane grasslands are generally dominated by Stipagrostis obtusa and the near endemic Aristida caerulescens (Poaceae). More locally Eragrostis papposa is dominant while in the closely grazed grasslands found in sheltered places on the summit of Emi Koussi in Tibesti the endemic Eragrostis kohorica (Poaceae) is the main grass species. Other endemic grasses found on Tibesti include Agrostis tibestica, Avena tibestica and Festuca tibestica (Poaceae).  These grasslands may also include several low scrub species such as Fagonia flamandii and the near endemic Anabasis articulata (Amaranthaceae) and Zilla spinosa (Brassicaceae). In other areas dwarf scrub becomes more prominent particularly on summits above 2600m. On Ahaggar these include Pentzia monodiana and Artemisia herba-Alba, whereas on Tibesti Pentzia monodiana is usually associated with Artemisia tilhoana and Ephedra tilhoana.  

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.

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.

Zohary, M. 1971. The Phytogeographical Foundations of the Middle East. In: Plant Life of South-West Asia. Eds. P. H. Davies, P. C. Harper and I. C. Hedge. The Botanical Society of Edinburgh.