Forests
Korup National Park - Tropical rainforest, Cameroon
The many faces of the Congo Basin forests
Seen one type of tropical rainforest, seen them all? Not quite. As one moves inland from the Atlantic coast, the type and wildlife composition of the rainforest changes in response to the climate and biogeographical influences.
A general profile
Compared to other forests on other continents, most forests of the Congo River Basin are relatively dry, receiving ‘only’ between 1,500 mm and 1,800 mm of rainfall per year.1There are some exceptions, such as the coastal Atlantic forests and the forest along the mountains to the east of the Congo River Basin, which receive more rainfall.
These areas also exhibit higher levels of biodiversity compared to the lowland rainforests. They are also the most threatened, because of their small size compared to the central forests, and also because they have been under human pressure for a relatively longer time.3
Evergreen rainforests
Evergreen or semi-evergreen rainforest is adapted to slightly more humid conditions than the semi-deciduous type and is usually found in areas where the dry period last no longer than 2 months. Plants in these forests keep their leaves around the year.The upper layer (35 – 45 m) of evergreen forests in the central part of the Congo River Basin is dominated by a few species such asGilbertiodendron dewevrei, Julbernadia seretii and Brachystegia laurentii. The high canopy blocks out light, which limits the growth of shrubs and grass below, and favours epiphytes.
Evergreen rainforests that receive some of the most intensive rainfall in the region are located in the coastal Atlantic region, which stretch from the coast to about 200 km inland. There, precipitation exceeds 3,000 mm per year in some areas.
These forests form the Atlantic Equatorial Coastal Forest ecoregion, where thousands of plants unique to tropical western Africa blanket the hills, plains and mountains. The area is known for its richness of forest mammals and includes lowland gorillas, chimpanzees, forest elephants and African buffalo.
Semi-deciduous forest
In these forests, trees lose their leaves during the dry season. Semi-deciduous forest occurs in areas where dry periods last 3 months. 5
At the boundaries of the Congo River Basin, most forested zones are semi-deciduous: deciduous trees make up the upper layer of the forest (up to 70%), mixed with evergreen species.
The semi-deciduous forest is richer in plant species than the evergreen forest.6 It is characterized by a mixture of species dominated by hackberry (Celtis spp), samfona(Chrysophyllum perpulchrum) and bark cloth tree (Antiaris welwitschii) among others. 7
The canopy of this kind of forest is characteristically undulating. Many commercial species are found in the semi-deciduous forest (e.g. Meliaceae, Tryplochiton scleroxylon, Chlorophora excelsa) of southeastern Cameroon, the Central African Republic and in northern Congo-Brazzaville. 8
Evergreen montane and sub-montane forests
These forests occur at altitudes higher than 1,000 m. The trees are smaller, they occur in higher numbers but the composition of species is relatively less diverse.In the Congo River Basin, the main regions of montane or sub-montane forests are found in the Albertine Rift and in coastal Central Africa.9
1 FORAFRI. Environnement Physique. Accessed: 7/10/05.
3 FORAFRI. Vegetation. Accessed: 7/10/05.
5 White F. 1983. The vegetation of Africa – A descriptive memoir to accompany the UNESCO/AETFAT/UNSO vegetation map of Africa. Series “Natural Resources Research” XX, Paris, UNESCO, 356 pp.
6 Mayaux et al. 2003. A land cover map of Africa. EC Joint Research Centre.
7 FAO. 2001. Global Ecological Zoning for the Global Forest Resources Assessment 2000 - FINAL REPORT. Forest Resources Assessment - WP 56, Rome.
8 Mayaux et al. 2003. A land cover map of Africa. EC Joint Research Centre.
9 Mayaux et al. 2003. A land cover map of Africa. EC Joint Research Centre.
