The tropical rainforest is Earth's most biologically diverse biome. It has four distinct layers - the emergent layer of tall trees, the upper canopy layer where most animals live, the understory layer of shrubs and small trees with constant high humidity, and the dark forest floor that receives less than 1% of sunlight. Despite low-nutrient soils from heavy rainfall and weathering, the rainforest supports a wide variety of adapted plant and animal species through nutrient recycling and specialized structures for gathering light.

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2. Specific description
Layers of the Rainforest
Climate
Soil
Rainfall
Vegetation
Adaptation
Animals
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Examples

3. The tropical rainforest is earth’s most complex
biome in terms of both structure and species
diversity.
It occurs under optimal growing conditions:
abundant precipitation and year round warmth.
There is no annual rhythm to the forest; rather
each species has evolved its own flowering and
fruiting seasons.
Sunlight is a major limiting factor.
A variety of strategies have been successful in the
struggle to reach light or to adapt to the low
intensity of light beneath the canopy.
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4. There are four very distinct layers of trees in a
tropical rain forest. These layers have been
identified as the emergent, upper canopy,
understory, and forest floor.
Emergent trees are spaced wide apart, and are 100
to 240 feet tall with umbrella-shaped canopies
that grow above the forest. Because emergent
trees are exposed to drying winds, they tend to
have small, pointed leaves. Some species lose their
leaves during the brief dry season in monsoon
rainforests. These giant trees have straight,
smooth trunks with few branches. Their root
system is very shallow, and to support their size
they grow buttresses that can spread out to a
distance of 30 feet.
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5. The upper canopy of 60 to 130 foot trees allows
light to be easily available at the top of this
layer, but greatly reduced any light below it.
Most of the rainforest's animals live in the upper
canopy. There is so much food available at this
level that some animals never go down to the
forest floor. The leaves have "drip spouts" that
allows rain to run off. This keeps them dry and
prevents mold and mildew from forming in the
humid environment.
The understory, or lower canopy, consists of 60
foot trees. This layer is made up of the trunks of
canopy trees, shrubs, plants and small trees.
There is little air movement. As a result the
humidity is constantly high. This level is in
constant shade.
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6. The forest floor is usually completely shaded,
except where a canopy tree has fallen and
created an opening. Most areas of the forest
floor receive so little light that few bushes or
herbs can grow there. As a result, a person can
easily walk through most parts of a tropical
rain forest. Less than 1 % of the light that
strikes the top of the forest penetrates to the
forest floor. The top soil is very thin and of
poor quality. A lot of litter falls to the ground
where it is quickly broken down by
decomposers like termites, earthworms and
fungi. The heat and humidity further help to
break down the litter. This organic matter is
then just as quickly absorbed by the trees'
shallow roots.
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7. Mean monthly temperatures are above 64 ° F;
precipitation is often in excess of 100 inches a
year. There is usually a brief season of reduced
precipitation. In monsoonal areas, there is a real
dry season, but that is more than compensated
for with abundant precipitation the rest of the
year.
The temperature in a rain forest rarely gets
higher than 93 °F (34 °C) or drops below 68 °F (20
°C)
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8. Oxisols, infertile, deeply weathered and
severely leached, have developed on the
ancient Gondwanan shields. Rapid
bacterial decay prevents the accumulation
of humus. The concentration of iron and
aluminum oxides by the laterization pro
cess gives the oxisols a bright red color
and sometimes produces minable deposits
(e.g., bauxite). On younger substrates,
especially of volcanic origin, tropical
soils may be quite fertile.
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9. Soil and Nutrient Recycling
Most tropical rainforest soils relatively poor in
nutrients. Millions of years of weathering and
torrential rains have washed most of the
nutrients out of the soil. More recent volcanic
soils, however, can be very fertile. Tropical rain
forest soils contain less organic matter than
temperate forests and most of the available
nutrients are found in the living plant and animal
material. Nutrients in the soil are often in forms
that are not accessible by plants.
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10. Constant warmth and moisture promote
rapid decay of organic matter. When a
tree dies in the rainforest, living
organisms quickly absorb the nutrients
before they have a chance to be washed
away. When tropical forests are cut and
burned, heavy rains can quickly wash the
released nutrients away, leaving the soil
even more impoverished.
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11. * An average of 50 to 260 inches (125
to 660 cm.) of rain falls yearly.
* rainfall is often more than 100
inches a year
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12. A vertical stratification of three layer of
trees is apparent.. These layers have been
identified as A, B, and C layers:
A Layer B Layer
C Layer
Shrub Layer Ground Layer

13. A layer: the emergents. Widely
spaced trees 100 to 120 feet tall and
with umbrella-shaped canopies
extend above the general canopy
of the forest. Since they must
contend with drying winds, they
tend to have small leaves and some
species are deci duous during the
brief dry season.
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14. B layer: a closed canopy of 80 foot
trees. Light is readily available at
the top of this layer, but greatly
reduced below it.
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15. C layer: a closed canopy of 60 foot
trees. There is little air movement
in this zone and consequently
humidity is constantly high.
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16. Shrub/sapling layer: Less than 3 percent
of the light intercepted at the top of
the forest canopy passes to this layer.
Arrested growth is characteristic of
young trees capable of a rapid surge of
growth when a gap in canopy above them
opens.
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17. Ground layer: sparse plant growth. Less
than 1 percent of the light that strikes
the top of the forest penetrates to the
forest floor. In such darkness few green
plants grow. Moisture is also reduced
by the canopy above: one third of the
precipitation is intercepted before it
reaches the ground.
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18. Tropical rainforest plants also have
adaptations to take in what little
sunlight is available on the dark forest
floor. Large leaves are common; they
increase the amount of sunlight a plant
can capture. Other plants, like orchids,
bromeliads and ferns, grow as epiphytes
high up in the canopy where there is
more sunlight.
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19. Colugo cuscus
Aye aye Agouti
wallaby
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20. Amazon
Western
Ghats
Madagascar Back to Main Menu

21. James Belleza
Nessy Cueto
Russel Castillo
Rachelle Ferrer
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