Geoscience Reference
In-Depth Information
Neotropical and African rainforests. This tree is widely distributed in the rainforest
of the Neotropics, but limited in the rainforest of West Africa. It is pollinated by
birds in both regions. Cerrillo has its origin in Africa about 45 mya and is thought
to have come to the Americas 15-18 mya.
Forest Structure
The structure of the African rainforest is similar to other tropical forests with three
canopy layers, a shrub layer, and a herbaceous layer (see Figure 3.10). Emergent
trees in this region are slightly shorter on average than those of the Neotropical and
Asian-Pacific rainforests. Emergent trees average 80-150 ft (24-45 m) in height.
Unlike the Neotropical rainforest, the emergent layer in the African rainforest is of-
ten dominated by only a few species within a forest stand. Emergents tend to be
shade tolerant when young and grow slowly under the canopy until a clearing
opens, at which point their growth rate increases and they rapidly fill the gap. Com-
mon trees in the emergent layer are members of the Caesalpinioideae subfamily of
the legume family and include tamarind, mopane, senna, and honey locusts. All
are tall and long-lived, some reaching ages of 1,000 years, although older trees are
now rare due to selective logging and deforestation. A single species often domi-
nates large areas. Single-species dominance is common in the African rainforest,
but it is less common in other regions within the Tropical Rainforest Biome. While
an acre of rainforest in the Neotropics may contain hundreds of tree species, that
same area in Africa may have less than 20. Trees found in the tropical rainforests
Figure 3.10 The structure of the African rainforest is similar to the other regions,
although lianas play a less significant role.
(Illustration by Jeff Dixon. Adapted from Rich-
ards 1952.)
