Geoscience Reference
In-Depth Information
Figure 1.1 Tropical Forest Biomes of the world.
(Map by Bernd Kuennecke.)
Tropical seasonal forests are broadleaved deciduous forests and evergreen dry for-
ests found in regions that are both warm year-round and strongly water limited
with several months of drought.
While both biomes have many things in common, they can be easily distin-
guished by climate, soils, vegetative structure, and types of plants and animals.
Tropical plant communities form a graded series from wet to dry. Yet this change
is so gradual that no clear boundary exists between the two biomes.
Some characteristics of the Tropical Rainforest Biome include more than 100 ft
(30 m) tall emergent trees, with buttressed bases, understory plants with large ever-
green leaves with rain-adapted ''drip tips,'' and hundreds of species of epiphytes
and woody vines that hang on trees throughout the forest canopy. On the margins
of the tropics, drier or xeric plant communities such as thorn forest have short trees
less than 15 ft (5 m) tall and lacking buttresses. They have relatively small com-
pound leaves and trunks armed with thorns. Trees of the Tropical Seasonal Forest
Biome fall in the middle of the spectrum, with broadleaf trees and vines that lose
their leaves at the start of the dry season and proceed to flower and fruit.
Tropical rainforests are densely populated by trees and others plants that form
many vegetative layers within the forest. The uppermost layers form the canopy.
As you move down through the canopy, each lower layer is influenced by the
upper layers. The highest canopy layer consists of scattered, very tall trees called
emergents that encounter extreme solar input (heat and light) as well as rainfall
and wind. The next canopy layer, below the emergent trees, is densely forested,
allowing little light to penetrate to the lower forest layers. Lower canopy layers
