Evergreen rainforestsEvergreen 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 as Gilbertiodendron 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 forestIn 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