CLIMATE

Page <1> <2>

The vegetation of Ethiopia is divided into eight major types.

Desert and semi-desert scrubland:
This vegetation type is characterized by draught tolerant plants. These include small trees and shrubs of species of Acacia. Commiphora, Boscia, Cadaba, Maerua and Zizyphus, succulent species of Euphorbia and Aloe, and grass species such as Dactyloctenium aegyptium and Panicum turgidum. These areas are very dry. The soils are alluvial and hence they are vulnerable to wind and water erosion. Because water is a scarce resource in such areas, the areas around watering points can be devoid of vegetation.

The Afar depression, the Ogaden, Lake Chew Bahir and the Omo delta have this vegetation type.

Acacia-Commiphora, small-leaved, deciduous woodland:
Acacia-Commiphora vegetation is characterized by draught tolerant trees and shrubs, with either small deciduous leaves or leathery persistent ones. The understorey is mainly composed of shrubby herbs less than one meter high and grasses. The trees and shrubs include Acacia tortilis, A. mellifera, Balanites aegypyiaca, various species of Commiphora, Capparis, Combretum and Terminalia. The small shrubby herbs include species of Acalypha, Barleria and Aerva.

Acacia-Commiphora woodlands occur mainly in the north, east, south and central parts of the country at altitudes between 900 and 1,900 m asl.

Moist evergreen forest:
This vegetation type is characterized by tall emergent and medium-sized trees, and by understorey shrubs. Emergent tree species typical of moist evergreen forests include Aningeria adolfi-friedericii, Albizia gummifera, A.grandibracteata, Macaranga capensis and Ocotea kenyensis. Typical understorey shrubs include Chionanthus mildbraedi and Psychotria orophilla. A number of endemic herbs and epiphytes, but not trees, are found in these forests.

Moist evergreen forests occur mainly in western and southwestern parts of the plateau in south Bale, north Borena, west Wellega and Illubabor zones of Oormia Region, and Kefa zone of Southern Nations, Nationalities and Peoples’ Region. In western and southwestern parts of the country, these forests occur at altitudes of between 1,500 and 2,500 m, where average annual temperatures are 180 C to 200 C, and an annual rainfall is between 1,500 and 2,400 mm. In Bale and Borena the forest occur up to 2,800 m asl, the annual rainfall is lower, only up to 1,500 mm. One of the most important moist evergreen forests in the southeast is the Harenna forest on the southern slopes of the Bale massif.

All these forests are severely threatened as they are under constant pressure from commercial timber merchants to supply the timber industry of the country as well as the local people for their own domestic and commercial needs.

Lowland, semi-evergreen forest:
This forest is characterized by a range of mainly semi-deciduous tree and shrub species and grasses. The woody species and emergent trees such as Celtis toka, Diospyros abyssinica, Malacantha alnifolia and Zanha golungensis. Typical shrubby spespinosa and Whitfieldia elongata.

This type of forest, which occurs in Gambella, has been described only recently (Friis, 1992). It occurs at altitudes between 450 and 600 m asl in areas with mean annual maximum temperature of 350 C to 380 C, mean annual temperatures of 180 C to 200 C, and annual rainfall of 1,300 to 1,800 mm. The forest occurs mainly on sandy soils, which are well drained but have ground water not far below the surface.

Combertum-Terminalia, broad-leaved, deciduous woodland:
this woodland is characterized by small trees with fairly large deciduous leaves, and an undderstorey of herbs and grasses which grow tall open areas in the valleys. The dominant trees and shrubs include various species of Combretum and Terminalia, Boswellia papyrifera, Lannea schimperi, Anogeissus leiocarpus and Stereospermum knuthianum; the solid-stemmed bamboo Oxytenanthera abyssinica is prominent in the western river valleys of Ethiopia. The grasses are dominated by tall species of Cymbopogon, Hyparrhenia, Echinochloa, Sorghum and pennisetum.

Combretum-Terminalia woodland occurs in the northwestern parts of the country particularly throughout Benshangul- Gumuz Region and much of Gambella Region. It is also found in the North and South Omo zones of Southern Nations, Nationalities and peoples’ Region.

The altitudenal range of this vegetation type is between 500 and 1,900 m asl. At the upper altitudnal limit it frequently abuts on to Afromontane humid forest. The woodland has developed under the influence of fire and is thus not adversely affected by controlled fires.

Dry Evergreen Montane Forest and Grassland Complex:
This vegetation type is characterized by small to large-sized trees and extensive grassland which are rich in legumes. The common trees species include Juniperus procera, Olea europaea subsp. Cuspidate, Celtis africana, Euphorbia ampliphylla, Mimusops kummel and Ekekergia capensis. Typical shrubs include Dracaena spp., Carissa edulis and Rosa abyssinica. The common grass species belong to the genera Hyparrhenia, Eragrostis, Panicum, Sporobolus, Eleusine and Pennisetum, and the legumes to Trifolium, Eriosema and Crotalaria. The ecotone between the forest and grasslands is occupied by Acacia woodland with Accacia abyssinica, A. negrii and A. pilispina as the most common trees. This forest/woodland/grassland complex is particularly important as it is home to a large number of endemic plants.

Dry evergreen montane forests, Acacia woodlands and grasslands occur in much of the highlands in the northern and northwestern, central and southeastern parts of the country. On the northwestern plateau, altitudinal limits of this vegetation type are found between 1,900 and 3,400 m asl where annual rainfall ranges between 800 and 1,500 mm. The average annual temperatures are between 14 and 180 C. on the southeastern plateau this vegetation type occurs between 1,500 and 2,200 m asl in areas with an annual rainfall of around 700 mm and average annual temperatures of between 20 and 250 C.

This is a zone where sedentary, cereal based agriculture has gone on for thousands of years. Consequently the areas under natural vegetation have dwindles as a result of anthropogenic activities. In many places the forests have been replaced by woodland and grassland on gentle slopes with deep soils, and by evergreen bush land on steeper slopes with thin soils.

Afro alpine and sub-afro alpine vegetation:
This vegetation type is characterized by small trees, shrubs and shrubby herbs at the lower altitudes, and giant herbs, small herbs and grasses, many of them forming hummocks or tussocks at the higher altitudes. Typical small tree and shrubby species include Erica arborea, E. trimera and Hypericum revolutum. Typical shrubby herbs include several species of Helichrysum. Among the giant and small herbs of this zone are the giant lobelia, Lobelia rhynchopetalum, Kniphofia foliosa, Bartsia petitiana and various Alchemilla species. Many of the typical grass species belong to genera Festuca, Poa and Agrostis.

Afro alpine and sub-afro alpine vegetation occurs in areas which are, on average above 3,200 m in altitude. Thus it occurs on the slopes and at the tops of the highest mountains in the country and is the major vegetation type of the two most important national parks in Ethiopia, Semien Mountains National Park and Bale Mountains National Park.

These high areas have a fragile environment where the vegetation experiences, as indicated by Hedberg (1957), a unique climate of summer every day and winter every night. Any tampering with the vegetation in such a fragile environment can have irreversible, negative consequences affecting both the uniqueness of the habitat and the continued existence of the life forms inhabiting it. The major threats to its continued existence are fire, grazing and barley cultivation.

Riparian and swamp vegetation:
This vegetation type is characterized by a range of tree and grasses. Typical tree species include: Celtis africana, Ficus sycomorus, Mimusops kummel, Tamarindus indica, Maytenus senegalensis, some Acacia spp. Kigelia aethiopum and Syzygium guineense. Swamps are dominated by sedges, ( especially species of Cyperus, Eleocharis and Scirpus), grasses, (especially species of Echinochloa), and many herbs.

Page <1> <2>

--------------------------------------------------------------------------------------------
BACK TO: Introduction// Historical Overview// Climate// Economy
--------------------------------------------------------------------------------------------