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of the Neotropics and Asia have limited distribution, but the trees of the African
rainforest occur throughout the region.
The B layer has an open canopy formed by 50-100 ft (15-30 m) trees. Trees in
this layer tend to be narrow. Woody vines and epiphytes found among the B-layer
trees can make up a majority of the layer's biomass. The C layer is composed of
smaller trees around 30-50 ft (5-15 m) tall. The branches of many trees in the B
and C layers are often intertwined, providing arboreal avenues for animals travel-
ing from one location to another. Together, the two layers form a closed canopy
(see Figure 3.11). The trees of both layers include members of the palm (Areca-
ceae), laurel (Lauraceae), aroid (Araceae), pepper tree (Piperaceae), and mela-
stome (Melostomataceae) families. The kola nut tree is an interesting lower canopy
tree from the tropical rainforest of West Africa. The seeds from this tree have been
used for centuries as a medicinal tonic.
African rainforests tend to have lower tree densities (the number of trees per
unit area) than the rainforests of the Neotropics or Asian Pacific. Studies reveal tree
densities in tropical rainforests range from 300 to 1,000 trees per 2.4 acres (1 ha).
African densities tend to be on the lower side of this number, with 300-600 trees
per hectare. The canopy of the African rainforest is rich in flowering trees, orchids,
Figure 3.11 African rainforest on Sao Tome Island, Republic of Sao Tome and Prin-
cipe. (Photo courtesy of Robert Drewes, Ph.D., California Academy of Sciences.)
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