Geoscience Reference
In-Depth Information
Figure 3.2 Tropical rainforest cover large areas of Bolivia along the Madidi River.
(Photo by author.)
in height. The tallest trees are found in the lowland tropical forests. Some emer-
gents have reached heights of 300 ft (90 m), but because of continuous deforesta-
tion, these trees are increasingly rare. These trees contend with strong drying winds
and tend to have small leaves. Some species may be semideciduous during the brief
dry season. Many trees within the Neotropical rainforest have spreading, flattened
crowns with branches radiating out from one or a few points like the spokes of an
umbrella. This evolutionary adaptation provides the tree with maximum surface
area exposed to the sun and limits the shading effect of the tree leaves on itself;
lower in the tree canopy, the pattern is less pronounced. Neighboring trees compet-
ing for light often modify this round flattened-crown shape. The B layer is com-
posed of a closed canopy of trees around 80 ft (25 m) tall. Light is readily available
at the top of this layer, but greatly reduced below it. Woody vines and epiphytes
are found among the B layer and can be the majority of biomass present in this
layer. The C layer is composed of smaller trees around 60 ft (18 m) tall. This creates
a closed canopy with little air movement and constantly high humidity below these
layers.
The Neotropical rainforest is characterized by high floral and faunal species di-
versity. Along with tree diversity, there is an enormous diversity of nontree species
of plants within the rainforest. Researchers studying forest understory have found
that the number of vine species within the Neotropical rainforest is greater than in
the rainforests of Africa and Asia. Many studies assessing the number of tree
