Afromontane

The Afromontane regions are subregions of the Afrotropical realm, one of the Earth's eight biogeographic realms, covering the plant and animal species found in the mountains of Africa and the southern Arabian Peninsula. The Afromontane regions of Africa are discontinuous, separated from each other by lower-lying areas, and are sometimes referred to as the Afromontane archipelago, as their distribution is analogous to a series of sky islands.

Afromontane Zones (transparent)
Afromontane Zones. I. West African and Cameroon highlands, II. Ethiopian and Arabian highlands, III. Western (Albertine) Rift, IV. Eastern Rift. V. Southern Rift, VI. Eastern Highlands, VII. Drakensberg

Geography

Afromontane communities occur above 1,500–2,000 metres (4,900–6,600 ft) elevation near the equator, and as low as 300 metres (980 ft) elevation in the Knysna-Amatole montane forests of South Africa. Afromontane forests are generally cooler and more humid than the surrounding lowlands.

The Afromontane archipelago mostly follows the East African Rift from the Red Sea to Zimbabwe, with the largest areas in the Ethiopian Highlands, the Albertine Rift Mountains of Uganda, Rwanda, Burundi, Democratic Republic of the Congo, and Tanzania, and the Eastern Arc highlands of Kenya and Tanzania. Other Afromontane regions include the Drakensberg range of southern Africa, the Cameroon Highlands, and the Cameroon Line volcanoes, including Mount Cameroon, Bioko, and São Tomé.

Flora

Although some Afromontane enclaves are widely separated, they share a similar mix of plant species which are often distinct from the surrounding lowland regions. Podocarps, of genera Podocarpus and Afrocarpus, are a characteristic tree, along with Prunus africana, Hagenia abyssinica, Juniperus procera, and Olea spp.. In the higher mountains, the Afromontane forest or woodland zone transitions to a higher Afroalpine zone of grasslands, shrublands, or moorlands.

The plant families Curtisiaceae and Oliniaceae are Afromontane endemics and family Barbeyaceae is a near-endemic. The tree genera Afrocrania, Balthasaria, Curtisia, Ficalhoa, Hagenia, Kiggelaria, Leucosidea, Platypterocarpus, Trichocladus, Widdringtonia, and Xymalos are Afromontane endemics or near-endemics, as are the plant genera Ardisiandra, Cincinnobotrys, and Stapfiella.

Distribution

Eastern Afromontane Biodiversity Hotspot (cropped)
Eastern Afromontane Biodiversity Hotspots

In South Africa, Afromontane forests cover only 0.5% of the country's land area. The Afromontane forests occur along the mountainous arc of the Drakensberg Range, from Limpopo Province in the northeast to the Western Cape Province in the southwest. The Afromontane forests generally occur in well-watered areas, including ravines and south-facing slopes. The Afromontane forests are intolerant of fire, and the frequent fires of the surrounding fynbos, savanna, and grassland limit the expansion of the forests. Despite their small area, the Afromontane forests of South Africa produce valuable timber, particularly the real yellowwood (Podocarpus latifolius), Outeniqua yellowwood (Afrocarpus falcatus), and stinkwood (Ocotea bullata).

Afromontane ecoregions

Tropical and subtropical moist broadleaf forests
Montane grasslands, shrublands, and woodlands
Deserts and xeric shrublands

References

  • White, F. (1983). The vegetation of Africa: a descriptive memoir to accompany the UNESCO/AETFAT/UNSO vegetation map of Africa by F. White. UNESCO, Paris.
  • Galley, C. & Linder, H. P. (2006) Geographical affinities of the Cape flora, South Africa. Journal of Biogeography 33 (2), 236-250.

External links

Albertine Rift

The Albertine Rift is the western branch of the East African Rift, covering parts of Uganda, the Democratic Republic of the Congo (DRC), Rwanda, Burundi and Tanzania.

It extends from the northern end of Lake Albert to the southern end of Lake Tanganyika.

The geographical term includes the valley and the surrounding mountains.

Albertine Rift montane forests

The Albertine Rift montane forests ecoregion, of the tropical moist broadleaf forest biome, are in the heart of Afromontane tropical central Africa.

Barbeya

Barbeya oleoides is the only species of its family (Barbeyaceae). It is a small tree native to the mountains of Somalia, Ethiopia, and the Arabian Peninsula. It can be found locally abundant in the transition zone between the dry, evergreen, Afromontane forests and lower-elevation evergreen bushlands.

The Barbeyaceae family is closely related to its ecological associate on the Horn, the Dirachmaceae family. Evidence on the molecular level has demonstrated this despite obvious morphological differences between the two families such as Barbeya having small, unisexual, petalless flowers, while the flowers of Dirachmaceae are characterized by their bisexuality, and their relatively large petals (and size in general).

Cape Floristic Region

The Cape Floristic Region is a floristic region located near the southern tip of South Africa. It is the only floristic region of the Cape (South African) Floristic Kingdom, and includes only one floristic province, known as the Cape Floristic Province.

The Cape Floristic Region, the smallest of the six recognised floral kingdoms of the world, is an area of extraordinarily high diversity and endemism, and is home to over 9,000 vascular plant species, of which 69 percent are endemic. Much of this diversity is associated with the fynbos biome, a Mediterranean-type, fire-prone shrubland. The economical worth of fynbos biodiversity, based on harvests of fynbos products (e.g. wildflowers) and eco-tourism, is estimated to be in the region of R77 million a year. Thus, it is clear that the Cape Floristic Region has both economic and intrinsic biological value as a biodiversity hotspot.

East African montane forests

The East African montane forests is a montane tropical moist forest ecoregion of eastern Africa. The ecoregion comprises several separate areas above 2000 meters in the mountains of South Sudan, Uganda, Kenya, and Tanzania.

Eastern Rift mountains

The East African mountains are a mountain region in the African Great Lakes, within Kenya, Uganda, Tanzania, Democratic Republic of the Congo, Rwanda and Burundi.

Erica arborea

Erica arborea (tree heath) is a species of flowering plant (angiosperms) in the heather family, Ericaceae. There are disjunct populations in Africa including the Ethiopian Highlands, the mountains of Ruwenzori and the Cameroon Mountains. In Africa it is normally referred to as giant heather. It is native to the maquis shrublands surrounding the Mediterranean Basin north to Bulgaria and west to Portugal and the Canary and Madeira Islands. Naturalised populations occur in south-eastern Australia.The wood, known as briar root (French: bruyère), is extremely hard and heat-resistant, and is used for making smoking pipes.

Ethiopian Highlands

The Ethiopian Highlands is a rugged mass of mountains in Ethiopia, situated in the Horn region in northeast Africa. It forms the largest continuous area of its elevation in the continent, with little of its surface falling below 1,500 m (4,900 ft), while the summits reach heights of up to 4,550 m (14,930 ft). It is sometimes called the Roof of Africa due to its height and large area. Most of the Ethiopian Highlands are part of central and northern Ethiopia, and its northernmost portion reaches into Eritrea.

Hagenia

Hagenia abyssinica is a species of flowering plant native to the high-elevation Afromontane regions of central and eastern Africa. It also has a disjunct distribution in the high mountains of East Africa from Sudan and Ethiopia in the north, through Kenya, Uganda, Rwanda, Burundi, Democratic Republic of Congo, and Tanzania, to Malawi and Zambia in the south.

It is known in English as African redwood, East African rosewood, brayera, cusso, hagenia, or kousso, in Amharic as kosso, and in Swahili as mdobore or mlozilozi. It is the sole species of genus Hagenia, and its closest relative is the Afromontane genus Leucosidea. Synonyms include Banksia abyssinica, Brayera anthelmintica, Hagenia abyssinica var. viridifolia and Hagenia anthelmintica.

It is a tree up to 20 m in height, with a short trunk, thick branches, and thick, peeling bark. The leaves are up to 40 cm long, compound with 7-13 leaflets, each leaflet about 10 cm long with a finely serrated margin, green above, silvery-haired below. The flowers are white to orange-buff or pinkish-red, produced in panicles 30–60 cm long.

It is generally found from 2000–3000 m elevation, in areas receiving 1000–1500 mm of rainfall annually. It can be found growing in mixed afromontane forest with Podocarpus, Afrocarpus, and other trees, and in drier afromontane forests and woodlands where Hagenia is dominant, or in mixed stands of Hagenia and Juniperus procera. It is often found near the upper limit of forest growth, giving way to giant heather zones above it.

Hagenia is used as a food plant by the larvae of some Lepidoptera species including turnip moth.

Highveld

The Highveld (Afrikaans: Hoëveld) is the portion of the South African inland plateau which has an altitude above roughly 1500 m, but below 2100 m, thus excluding the Lesotho mountain regions to the south-east of the Highveld. It is home to some of the country's most important commercial farming areas, as well as its largest concentration of metropolitan centres, especially the Gauteng conurbation, which accommodates one-third of South Africa's population.

Hypericum revolutum

Hypericum revolutum is a shrub or small tree in the genus Hypericum native to Arabia and Africa. It is evergreen, with leaves opposite, closely spaced and crowded at the ends of branches, c. 20 × 5 mm, green to slightly glaucous, sessile, clasping at the base. Single bright yellow flowers form at the ends of branches, up to 5 cm in diameter, blooming from June to November. Fruit is a reddish-brown capsule, up to 13 × 10 mm.

Hypericum revolutum is characteristic of the Afromontane vegetation, found from 1400 – 2593 meters elevation, and ranging from southwest Arabia through the Afromontane zones of eastern Africa to the Cape; it is also found in the Cameroon Highlands and Bioko, and on Madagascar, the Comoro Islands, and Réunion. It grows along streams in montane grassland and forest fringes.

Jos Plateau

The Jos Plateau is a plateau located near the centre of Nigeria. It covers 8600 km² and is bounded by 300-600 m escarpments around much of its circumference. With an average altitude of 1280 m, it is the largest area over 1000 m in Nigeria, with a high point of 1829 m, in the Shere Hills. The plateau has given its name to the Plateau State in which it is found and is itself named for the state's capital, Jos.

Juniperus procera

Juniperus procera (known by the common English names African juniper, African pencil-cedar, East African juniper, East African-cedar, and Kenya-cedar) is a coniferous tree native to mountainous areas in Africa and the Arabian Peninsula. It is a characteristic tree of the Afromontane flora.

Knysna-Amatole montane forests

The Knysna-Amatole montane forests ecoregion, of the Tropical and subtropical moist broadleaf forests Biome, is in South Africa. It covers an Afromontane area of 3,100 square kilometres (1,200 sq mi) in South Africa's Eastern Cape and Western Cape provinces.

Loma Mountains

The Loma Mountains are the highest mountain range in Sierra Leone. The highest peak is Mount Bintumani which rises to a height of 1,945 metres (6,381 ft). The area has been designated a non-hunting forest reserve since 1952. The reserve covers an area of 33,201 hectares.

Mount Cameroon

Mount Cameroon is an active volcano in Cameroon near the Gulf of Guinea. Mount Cameroon is also known as Cameroon Mountain or Fako (the name of the higher of its two peaks) or by its indigenous name Mongo ma Ndemi ("Mountain of Greatness"). It is the highest point in sub-Saharan western and central Africa, the fourth-most prominent peak in Africa, and the 31st-most prominent in the world.

The mountain is part of the area of volcanic activity known as the Cameroon Volcanic Line, which also includes Lake Nyos, the site of a disaster in 1986. The most recent eruption occurred on February 3, 2012.

Mount Cameroon and Bioko montane forests

The Mount Cameroon and Bioko montane forests ecoregion, of the tropical and subtropical moist broadleaf forests Biome, are in Afromontane habitats in Cameroon and Equatorial Guinea of Africa.

Widdringtonia schwarzii

Widdringtonia schwarzii (Willowmore cedar or Willowmore cypress, Afrikaans: Baviaanskloof-seder) is a species of Widdringtonia native to South Africa, where it is endemic to the Baviaanskloof and Kouga Mountains west of Port Elizabeth in Eastern Cape Province; it occurs on dry rocky slopes and crags at 600-1,200 m altitude. It is threatened by habitat loss, particularly by wildfire. The Willowmore cypress is a protected tree in South Africa.It is a medium-sized evergreen tree growing to 20–25 m (formerly known to 40 m) tall. The leaves are scale-like, 1.5 mm long and 1 mm broad on small shoots, up to 10 mm long on strong-growing shoots, and arranged in opposite decussate pairs. The cones are globose to rectangular, 2–3 cm long, with four scales. It is closely related to Widdringtonia wallichii from Western Cape Province, being most easily distinguished by its larger seeds with a short seedwing.

Widdringtonia wallichii

Widdringtonia wallichii previously Widdringtonia cedarbergensis (Clanwilliam cedar or Clanwilliam cypress) is a species of Widdringtonia native to South Africa, where it is endemic to the Cederberg Mountains northeast of Cape Town in Western Cape Province. It is threatened by habitat loss and protected in South Africa under the National Forest Act (Act 84) of 1998.It is a small evergreen tree growing to 5–7 m (rarely to 20 m) tall. The leaves are scale-like, 1.5 mm long and 1 mm broad on small shoots, up to 15 mm long on strong-growing shoots, and arranged in opposite decussate pairs. The cones are globose to rectangular, 2–3 cm long, with four scales.

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