The Bale Mountains of Ethiopia

Afroalpine flora

On the roof of Africa: bogs in the distance and everlastings in the foreground. Botanizing on the roof of Africa Photo: S. Siebert. The Bale Mountains of Ethiopia

by Stefan Siebert, Department of Botany, University of Zululand and Syd Ramdhani, Department of Botany, Rhodes University

Like mountains on top of mountains, the higWands of highest at 4 377 m above sea level: the second highest point Ethiopia rise 1 500 m above a plateau that already lies at in Ethiopia. 2 500 m above sea level and comprises 80% of the landmass The Bale Mountains lie within the tropics of the northern of Africa above 3 000 m; better known as the 'roof of Africa'. hemisphere and the climate, high rainfall and mainly damp, The Bale Mountains on the southern higWands are charac­ cloudy weather is typical of a high altitude mountainous terized by numerous spectacular volcanic peaks, beautiful region. The year has three seasons: dry from November to alpine lakes and unspoiled mountain streams. A large pro­ February, early wet from March to June, and wet from July 2 portion of these mountains are protected in the 2 500 kIn to October. Summer days can reach maximum temperatures Bale Mountains National Park some 400 kIn south of Addis of 30°C, with minimum winter night temperatures dropping Ababa. well below freezing point. On cold, clear nights, heavy ground The Harenna escarpment that runs from east to west frosts are common. divides the National Park. A high altitude plateau lies north The basalts of the Bale Mountains support a rich diversity of the escarpment, averaging around 4 800 m above sea of plant communities. High rainfall and variation in altitude level. South of the escarpment the topology drops abruptly, and topography result in clear zonation of vegetation, similar and then slopes gradually down to an altitude of 1 500 m at to the patterns of zonation evident on most east African the park's boundary. mountains. Some plant genera are shared and are common The Sanetti plateau in the north is the most extensive to many of these mountains (e.g. Kniphofia, Afrocarpus and afroalpine (the distinctive flora of the uppermost parts ofhigh Erica) although species may differ. mountains) area in Africa, its ancient volcanic rocks dissect­ Lowlands ed by many rivers and streams that have cut deep gorges, The Weyb River, which rises in the Bale Mountains, formed and created spectacular waterfalls. Several massifs rise from the extensive underground cavern systems at Sof Omar as it the plateau. Of these, Tuilu Deemtu (Red Mountain) is the channelled through the limestone foothills. Numerous

54 June 2004 Veld&Flora Commiphora (corkwoods) and Acacia Terminalia brownii (weiba) and Ziziphus flora vegetates moist river banks. species, many of which are also found mucronata (buffalo-thorn). Dracaena Exposed bedrock along the road is in southern Africa, dominate these ellenbeckiana (dragon tree) is a com­ inhabited by the xerophyte, Xerophyta limestone hills. mon understorey shrub. humilis. The vegetation is typical dry, thorny Forbs (dwarf shrubs or woody plants Coffea arabica is found throughout savanna with wooded grasslands and found in grasslands) are also common, the country at this altitude (1 500 m). resembles the 'mixed bushveld' of especially succulents such as Coffee originates from the horn of South Africa. Conspicuous tree species Caralluma speciosa, Cissus quadrangu­ Africa and Ethiopia is the centre of its include Balanites aegyptiaca (single laris, Plectranthus puberulentus and genetic diversity. The shrub grows as a green-thorn), Combretum molle (velvet Pyrenacantha malvijolia, and different semi-wild crop in moist montane for­ bushwillow), Grewia pubescens species of Aloe, Euphorbia and Kleinia. est, as a cultivated crop with artificial (raisin), Maerua angolensis (bead­ A blue-flowered pioneer, Blepharis shade and watering, or as garden plant bean), Pappea capensis Uacket-plum), edulis, colonizes roadsides and, in con­ in backyards with other fruit trees. Steganotaenia araliacea (carrot-tree), trast, the white-flowered Kanahia lani- Another crop found at this altitude is

June 2004 Veld&Flora 55 Eragrostis tef(teff), a cereal used in the grass Pennisetum villosum (white fox­ Escarpment preparation of Ethiopia's staple food tail), the north African endemic Beyond the undulating hills of the 'ingera'. Ethiopia has over 100 species Solanum marginatum (white-edged wide plains, an afromontane forest belt of cultivated crops and their wild nightshade), and scattered specimens stretches up the escarpment to about relatives. of the flat crowned Acacia abyssinica 3 200 m, which is the upper limit of the Plains (highland umbrella-thorn). tree zone apart from isolated remnants The Bale Mountains are surrounded Also visible are magnificent speci­ in higher lying protected valleys. To the by wide, fertile plains below 2 000 m mens of Ajrocarpus falcatus (small­ north of the Harenna escarpment the above sea level that are extensively leaved or Outeniqua yellowwood), rem­ landscape is characterized by patches planted for wheat production. Towards nants of forests that once covered the of formerly extensive forests, dominat­ the main towns vast areas are also hillsides. A very interesting feature of ed by Juniperus procera and Hagenia planted with Eucalyptus globulus the roadsides is the planted hedges of abyssinica (East African rosewood). (Tasmanian blue gum) and Cupressus Euphorbia abyssinica (Abyssinian can­ Schefflera abyssinica (Abyssinian false lusitanica (Mexican cypress), and closer delabra) that are cut back 1.5 to 2 m cabbage tree), Maesa lanceolata (false to the escarpment with the indigenous high. At lower altitudes locals grow assegai) and Rapanea simensis (Simien Juniperus procera (African juniper). Ensete ventricosum (false banana), beech) grow in these open forests and Conspicuous plants of the road verges which they harvest for the starch Rosa abyssinica (white Abyssinian next to the fields include the invasive stored in the stem and leaf bases. rose) scrambles among the trees. The

• • •

• • • • .. • • • . .

ABOVE: The yellow flowers of Bidens macroptera brightens the extremely species­ rich rocky grasslands. LEFT: Human disturbance has caused beautiful 'gardens' of the torch lily, Kniphofia foliosa. Photos: S. Siebert. LEFT: The dense vegetation of the Erica­ Alchemilla-Helichrysum heathlands reminded us of the fynbos. Photo: S. Siebert. BELOW: Ethiopia, and the Bale Mountains National Park. Map by Sally Adam, Technodraft.

• • •• •

•

large, endemic composite Solanecio stinkwood), Croton macrostachyus (bis­ This species parallels Kniphojia gigas (nobe) is common in damp areas. sana), Erythrina brucei (coral tree), caulescens of the Drakensberg in beau­ The southern tree zone beneath the Ocotea kenyensis (northern ty and localized abundance. Bidens Harenna escarpment is characterized stinkwood), Olea hochstetteria (iron­ macroptera is a yellow-flowered endem­ by yellowwood forests interspersed wood olive), Syzygium guineense ic of the rocky grasslands on lower with groves of Arundinaria alpina subsp. afromontanum (pointed-leaf mountain slopes. (mountain bamboo). These southern waterberry) and Trema orientalis In the vicinity of the spectacular forests are much denser with a greater (pigeonwood) become more abundant. Sebsebe Washe rock formation, the diversity of species. Grasslands occasionally develop grassland is full of geophytes including Trees reach heights of 30 m and are between forests due to impeded Gladiolus longispathaceus. Other fre­ covered iI?- epiphytes, creepers and drainage, marshy conditions along quently encountered genera with lianas. Dominant trees include streams or human activities. They con­ indigenous representatives include Buddleja polystachya (anfar), tain dense stands of the scrubby aro­ Geranium, Oxalis, Plectranthus, Ekebergia capensis (Cape ash), matic Artemisia afra (African worm­ Scabiosa and Sedum. May tenus addat (silky bark), Nuxia con­ wood) and grey-leaved Helichrysum Subalpine gesta (brittlewood), Pittosporum viridi­ splendidum (Cape gold) with bright yel­ Above the tree line, reaching up to florum (cheesewood), Prunus africana low, papery flowers. 3 500 m above sea level, is a subalpine (African almond) and Schefflera volken­ In higher altitude grasslands, belt of ericaceous heathland. Frequent sii (ansha). Dense thickets of rapidly endemic flowering plants such as mists support a dense growth of lichen, growing edible mountain blackberry, Acanthus sennii and Echinops ellen­ mosses, wildflowers and grasses Rubus steudneri, grow in the wet sea­ beckii can be seen on the margins of beneath small trees. Hypericum revolu­ son. At the lower levels of the southern remnant forest patches. At lower alti­ tum (giant tree wort) with its golden yel­ tree zone (2000 m and below), the tudes human disturbance has resulted low flowers occurs frequently with species composition of trees changes. in beautiful 'botanical gardens', where Erica arborea (tree heather) at lower Allophylus abyssinicus (forest false­ fields with masses of Kniphojia foliosa altitudes in the forest/heathland tran­ currant), Celtis africana (white (torch lily) make for a spectacular sight. sition. Pastoralists often burn the

June 2004 Veld&Flora 57 :....._------~ ABOVE RIGHT: Flowering specimens of Carduus in the afroalpine lone. ABOVE LEFT: Echinops ellenbeckii with its characteristic ball-shaped flowers is unmistakable on the margins of forest patches. LEFT: A homestead surrounded by Hypericum revolutum. (Note the re­ sprouting Erica arborea in the fore­ ground.) Photos S Siebert

heather in an attempt to increase 'the flower heads, and Rubus erlangeri, with tussock grasses such as Pentaschistis grass layer, -resulting in stunted, re­ its unusually elongated and pointed minor and Festuca abyssinica. Plant sprouting trees. Frequently-occurring sepals. community patterns in this zone are herbaceous genera include Festuca, Afroalpine determined by slope, drainage and Hebenstretia, Romulea, Swertia and Afroalpine refers to the peculiar flora rodent activity. Pioneers are common, Viola. At higher altitudes Alchemilla of the uppermost parts of high moun­ colonizing soil that is continuously haumannii (lady's mantle), Erica tains. On the Bale Mountains this zone moved by giant mole rats, and include trimera (asta) and Helichrysum cit­ starts at about 4 000 m above sea level Arabidopsis thaliana, Erophila vema rispinum (spiny everlasting) form and is recognizable by its capping of and Thlaspi alliaceum. Rocks are cov­ dense, localized stands among the tree more recent lava flows that created ered by many species of mosses and heather in the transition zone with the spectacular rock formations. High lichens. Vegetation in flat areas below afroalpine belt. peaks are covered by bare rock or the peaks include many cushion-form­ Endemics associated with the erica­ exposed soils, vegetated only by small ing everlastings like Helichrysum cit­ ceous heathlands include Echinops but hardy herbs like Dipsacus pinnati­ rispinum, H. cymosum, H. jormosissi­ longisetus, with its conspicuous large fidus and Helichrysum splendens, and mum and H. splendidum; and typical

58 June 2004 Veld&Flora cushion plants such as Geranium kili­ Drakensberg as the East African unique plant life, but is also home to mandscharicum and Polygonum mountains. Like the other high altitude endemic mammals such as the Simien afromontanum. Plants frequently areas of East Africa, some plants in red wolf, mountain nyala, Menilek's encountered along drainage lines and Ethiopia have developed giant forms. bushbuck and giant molerat. It is also bogs include Alchemilla haumannii and Lobelia rhynchopetalum (giant lobelia) a birder's heaven, containing many the tufted sedge, Carex monostachya. A is the most noticeable in the Bale species endemic to Ethiopia. peculiar Carduus species and the blue Mountains: their silhouettes against This major watershed of Ethiopia and flowered Myosotis keniensis occur on the horizon on the Sanetti Plateau, and Somalia is not without threats. In the rock outcrops. their reflections in the numerous small Bale National Park pressure is placed In the Drakensberg, which also has a lakes make them unmistakable. on the natural vegetation by overgraz­ basaltic geology but where altitude Another giant lobelia, L. gibberoa Uibr­ ing, fire for controlling woody vegeta­ does not exceed 3 500 m above sea ra), is a smaller, spindly species that tion and deforestation. The park has level, a similar Erica-Helichrysum occurs in the southern forests below not been legally gazetted and people alpine heath occurs between 2 900 ­ the Harenna escarpment. are permitted to live with their livestock 3 500 m: a significantly lower altitude Unfortunately these graceful forms on the sensitive Sanetti plateau and than in the Bale Mountains. Altitudinal are not present in southern Africa, along the Harenna Forest. Fortunately effects have resulted in intermingling of probably because of our lower alti­ WWF has taken note of this situation montane forest and ericaceous belts tudes. The Ethiopian afroalpine moun­ and have initiated a project to address and these are not as distinct in the tain refuge is not only renowned for its responsible conservation.

Acknowledgements The authors thank Mr Jonathan Timberlake, Prof Ibb Friis, Dr Alan Paton, Dr David Goyder and Prof Peter Linder for field identifications. SABONET, NRF and IAPT is thanked for funding the authors' attendance of the AETFAT Congress and post-congress tour.

Further reading Friis, I, 1986. Zonation of forest vegetation on the south slope of Bale Mountains, south Ethiopia. Ethiopian Journal of Science 9: 29-44. Hedberg, O. 1986. The afro-alpine flora of Ethiopia. Ethiopian Journal of Science 9: 105-110. Hillman, C. & Hillman, S. 1990. Bale: Highland wilderness. Ethiopian Tourism Commission, Addis Ababa. Linder, P. 1996. Giants on the equator. African Environment & Wildlife 4: 68-75. Tadessa, M. 1991. Some endemic plants of Ethiopia. Ethiopian Tourism Commission, Addis Ababa.

BELOW: Atypical high altitude bog with giant lobelias in the background. Photo: S. Siebert.

June 2004 Veld&Flora 59