Congolian Lowland Evergreen Forest
This, as expected, is one of the most species rich vegetation types in the BioProvince, but species composition is extremely varied. In the Bakossi area and along the Mungo River common canopy trees include Allanblackia floribunda, Berlinia bracteosa, Diospyros mannii, Eriocoelum macrocarpum, Hylodendron gabonensis, Klainedoxa gabonensis, Microcos coriacea, Octoknema affinis, Oxystigma gibertii, Panda oleosa, Quassia sivestris, Scottellia klaineana, Stromposa grandiflora, Tetrapleura tetraptera and the endemic Loesenera talbotii (Fabaceae). The main emergent species are Baillonella toxisperma, Ceiba pentandra and Desbordesia glaucescens. Surprisingly, these forests also include a number of monotypic stands a phenomenon normally associated of temperate forests. The main species forming these mono-stands are Gilbertiodendron dewevrei and Loesenera talbotii. Among the species rich shrub layer common species include Antidesma laciniatum, Crotonogyne preussii, Discoclaoxylon hexandrum, Erythrococca anomala, Glossocalyx brevipes, Massularia acuminata, Tricalysia gossweileri and the endemic Pavetta rigida (Rubiaceae) and Psychotria leptophylla (Rubiaceae). Lianas are also abundant with species like Atractyogyne gabonica, Cissampelos owariensis, Jateorhiza macrantha, Lavigeria macrocarpa, Microcos barombiensis and Terenna fusco-flava. Common herbs are Anchomanes difformis, Commelina capitata, Cyanastrum cordifolium, Dorstenia ciliata, Nephthytis poissonii, Palisota barteri and Stenandrium guineense. Other endemic plants found here include Cyprus microcristatus (Cyperaceae), Diospyros kupensis (Ebenaceae), Ossiculum aurantiacum (Orchidaceae), Psydrax bridsoniana (Rubiaceae) and Stelechantha arcuata (Rubiaceae).
Congolian Semi-Deciduous Woodland
Now restricted to a few places such as the Loum Forest Reserve in Cameroon these forests may once have been continuous with the semi-deciduous forest of Mount Cameroon. Their presence, however, is somewhat surprising in an area that receives up to 4 m of rain per annum when just 2 m is sufficient to support evergreen forest. Their occurrence seems more likely to relate to the free-draining nature of the underlying volcanic substrate. The main canopy trees include species of Triplochiton, Celtis adalfi-triderici and C. philippensis, while other characteristic trees include Celtis gomphophylla, C. zenkeri, Cyclicodiscus gabunensis, Khaya ivorensis, Milicia regia, Piptadeniastrum africanum, Sterculia oblonga, Terminalia superba and Trilepisium madagascariense. However, much of the undergrowth of these forests has been lost to human activities. Nevertheless, they still include several endemic plants such as Beilschmiedia crassipes (Lauraceae), Crotonogyne impedita (Euphorbiaceae), Memecylon griseo-violaceum (Melastamataceae), Microberlinia bisulcata (Fabaceae) and Thyrosalacia racemosa (Celastraceae). On the other hand, some of these appear to be very narrow endemics and may now be extinct.
Congolian Sub-Montane Forest
Also known as cloud, moss and elfin forest these occur at altitudes ranging from 800-1900 m where average tree height is just 3 m. Species composition varies somewhat with altitude but in the Kupe, Mwanenguba and Bakossi mountains common tree species typically include Allanblackia gobonensis, Chionanthus africanus, the tree fern Cyathea manniana, Dasylepis racemosa, Garcinia smeathmannii, Pentadesma grandifolia, Polyscias fulva, Pseudagrostistachya african, Quassia sanguinea and endemic species such as Cyclicomorpha solmsii (Caricaceae), Macaranga occidentalis (Euphorbiaceae), Oncoba lophocarpa (Saliacaceae) and Rhaptopetalum geophylax (Lecythidaceae). Typical shrub layer species are Psychotria peduncularis, Sorindeia grandifolia and the endemic Coffea montekupensis (Rubiaceae), Myrianthus preussii subsp. preussii (Cecropiaceae) and Pauridiantha paucinervis (Rubiaceae). Among the terrestrial herbs are Buforrestia mannii, Cardamine trichocarpa, Polyspatha paniculata, Sanicula elata and the endemic Graptophyllum glandulosum (Acanthaceae). The herb layer is also characterized by many saprophytic species. In fact, the montane forests of Mount Kupe and the Bakossi Mountains possibly support the most diverse assemblage of vascular saprophytes on the planet and several, such as Afrothismia pachyantha (Burmanniaceae) and Kupea martinetugei (Truridaceae), are endemic to these mountains. Likewise the epiphytic flora is also extremely diverse and possibly the richest in Africa. In addition to the more typical epiphytic groups (mainly pteridophytes and orchids), taxa from many other families are represented including Anthocleista scandens (Loganiaceae), Chassalia petitiana (Rubiaceae), Dorstenia astyanactis (Moraceae), Procris crenata (Urticaceae), Rhipsalis baccifera (Cactaceae), Utricularia mannii (Lentibulariaceae) and the endemic Begonia duncan-thomasii (Begoniaceae), Bulbostylis densa var. cameroonensis (Cyperaceae) and Preussiella kamerunensis (Melastomataceae). Certain species of Schlefflera and many species of Ficus begin life as epiphytic shrubs but later become terrestrial trees through the “strangler” procedure. Lianas are well represented with species such as Jasminum bakeri, Pararistolochia ceropegioides and Uvaria heterotricha.
Congolian Montane Forest
These forests are characteristic of uplands ranging in elevation from 2000-2050 m and can be found, for example, on the Mwanenguba caldera and Mount Kupe. Their canopies rarely exceed about 8 m and typically include Bersama abyssinica, Cassipourea malosana, Carapa grandiflora, Clausena anisata, Ilex mitis, Olea capensis, Podocarpus milanjianus, Prunus africana, Schefflera abyssinca and the endemic Ixora foliosa (Rubiaceae), Schefflera mannii (Araliaceae) and Syzygium staudtii (Myrtaceae). The main understorey shrubs are Cassine aethiopica, Discopodium penninervium, Maytenus buchananii, Rhamnus prinoides, Xymalos monospora and the endemic Batesanthus purpureus (Asclepiadaceae), Pavettia hookeriana, P. kupensis (Rubiaceae) and Psydrax dunlapii (Rubiaceae). Lianas include Clematis simense, Embelia schimperi, Jasminium preussii, Stephania abyssinica and the endemic Dalbergia oligophylla (Fabaceae) and Embelia mildbraedii (Myrsinaceae). Some of the main herbs are Mimulopsis solmii and the endemic Acanthopale decempedalis (Acanthaceae), Brachystephanus giganteus, B. kupensis (Acanthaceae), Oreacanthus mannii (Acanthaceae) and Plectranthus insignis (Lamiaceae). There is some evidence to suggest that a number of under storey herbs undergo synchronous mass flowering.
Congolian Montane Grassland
Natural or semi-natural mountain grasslands occur at altitudes ranging from 1900-2050 m in upland areas such as Mwanenguba and Mount Kupe. In the former they can be found girdling the shoulders of the Caldera, while on Kupe they often cap inselbergs embedded in the mountain. However, there appears to be no grassland species common to these two areas. On Mwanenguba the dominant grass is Sporobolus africanus, which occurs with a thin scattering of other species. Several of these, such as Cyanotis barbata, Habenaria peristyloides, Lactuca inermis and Nephrolepis undulata are perennials with underground rootstocks. However, most of the species are annuals that disappear during the dry season. These include Antherotoma naudinii, Conyza pyrrhopapa, Crotalaria subcapitata, Desmodium uncinatum, Galinsoga parviflora, Galium simense, Indigofera mimosoides, Lactuca inermis, Linum volkensii, Neontonia wrightii, Polygala palmata, Sebaea brachyphylla, Spermococe pusilla and the endemic Wahlenbergia ramosissima (Campanulaceae). On Kupe the dominant grass is Panicum hochstetteri. The only other common species is Gladiolus aequinoctialis. Less common species are Lobelia hartlaubii, Loudetiopsis trigemina, Monocymbium ceresiiforme, Plectranthus decumbens and the endemic Peucedanum kupensis (Apiaceae).
Congolian Crater Lakes
Crater lakes occur throughout the Cameroon Highlands. Lake Nyos in the Bamenda Highlands is probably the best known mainly because it released a cloud of poisonous gas in 1986 causing a number of fatalities. However, one of the best studied is Lake Edib but it is far from typical. A mattress of Sphagnum planifolium largely covers the surface water. On top of this is a distinct zonation of vascular plants. In the zone adjacent to open water species such as Cyperus pectinatus, Elaeocharis variegata, Oplismenus hirtellus and Pneumatopteris afra predominate. Moving landward a more species-rich zone occurs with species like Drosera madagascariensis, Habenaria weileriana, Laurembergia tetrandra, Ludwigia abyssinica, Pseudolycopodiella affine, Senecio ruwenzoriensis and Satyrium crassicaule. Another unexpected feature of this zone are prostrate climbers such as Secamone recemosa and Urera trinervis and obligate epiphytes like Begonia ampla and the endemic Impatiens letouzeyi (Balsaminaceae). There are several other clearly defined zones culminating in a belt of lake margin species with Cynorkis anacamptoides, Eulophia horsfallii, Floscopa glomerata, Habenaria procera, Polygonum setosulum, Rhynchospora corymbosa, Schoenoplectus mucronatus and the endemic fern Athyrium ammifolium (Woodsiaceae).
Further information required.
References
Adams, C. D. 1957. Observations on the fern flora of Fernando Po. I. A description of the vegetation with particular reference to the Pteridophyta. Journal of Ecology, 45: 479-494.
Boubli, J. P., Eriksson, J., Wich, S., Hohmann, G. & Fruth, B. 2004. Mesoscale transect sampling of trees in the Lomako-Yekokora interfluvium, Democratic Republic of Congo. Biodiversity and Conservation, 13: 2399-2417.
Brenan, J. P. M. 1978. Some aspects of the phytogeography of tropical Africa. Annals of the Missouri Botanical Garden, 65: 437-474.
Campbell, D. G. & Hammond, H. D. 1989. Floristic Inventory of Tropical Countries. The New York Botanical Garden.
Cheek, M., Onana, J. M., Pollard, B. J., Darbyshire, I. & Csiba, L. 2000. The Plants of Mount Oku and the Ijim Ridge, Cameroon. A Conservation Checklist. Royal Botanic Gardens, Kew.
Cheek, M., Pollard, B. J., Darbyshire, I., Onana, J. M. & Wild, C. 2004. The Plants of Kupe, Mwanenguba and the Bakossi Mountains, Cameroon. A Conservation Checklist. Royal Botanic Gardens, Kew.
Hall, J. B. 1971. Environment and vegetation on Nigeria’s highlands. Vegetatio, 23: 339-359.
Hall, J. B. & Medler, J. A. 1975. The botanical exploration of the Obudu Plateau area. Nigerian Field, 40: 101-115.
Keat, R. W. J. 1955. Montane vegetation and flora in the British Cameroons. Proceedings of the Linnean Society of London, 165: 140-143.
Keay, R. W. J. 1979. A botanical study of the Obudu Plateau and Sonkwala Mountains. Nigerian Field, 1979: 106-119.
Livingstone, D. A. 1967. Postglacial vegetation of the Ruwenzori Mountains in equatorial Africa. Ecological Monographs, 37: 25-52.
Morton, J. K. 1986. Montane Vegetation. In: Plant Ecology in West Africa. Ed. G. W. Lawson. John Wiley & Sons Ltd.
National Report on the Status of Biodiversity in S.Tomé and Príncipe. 2007. Ministry for Natural Resources and the Environment. Directorate General for Environment. Democratic Republic of São Tomé and Príncipe.
Owiunji, I., Nkuuta, D., Kujirakwinja, D. Liengola, I., Plumptre, A., Nsanzurwimo, A., Fawcett, K., Gray. M. & McNeilage. A. (undated). The Biodiversity of the Virunga Volcanoes. Wildlife Conservation Society, Institute of Tropical Forest Conservation, International Gorilla Conservation Programme and others.
Richards, P. W. 1963. Ecological notes on west African vegetation. II. Lowland forest of the southern Bakundu Forest Reserve. Journal of Ecology, 51: 123-149.
White, F. 1983. The Vegetation of Africa. UNESCO.