1. Course: Biogeography
Date: March 5, 2013

2.  A rainforest is a thick forest in moderately warm to
very hot areas which have heavy rainfall and high
humidity .

4.  Tropical Rainforests are found between 5-10 degrees
north and south of the equator. Some countries /areas
that Tropical forest biomes are found:
 Brazil
 Indonesia
 Malaysia
 Madagascar
 Parts of Australia
 Thailand
 Amazon Basin
 Congo

5.  High annual temperature
(27- 30 degree)
 Temperature is uniform
 High humidity and cloud
cover.
 no dry season.
 Mostly convectional
rainfall.
 Average rainfall is
between 1,200mm to
3000mm per year.

6.  Latosols or ferralitic soils
 Extensive chemical weathering resulting from the
high rainfall and temperature leads to the
development of deep soils, often 20m to 30m deep
 The soils have a loose structure and are rapidly
eroded once the protective layer of vegetation is
removed
 Except for the top few inches, soil fertility is poor

7. Thick litter
layer
Thin dark humus
layer
Many soil organisms A typical latosol
mix soil well  profile
Oxides of iron and
A and B aluminium stain soil red
horizons 
Hydrated oxides produces
red/yellow colouration
Clays produced by intense
chemical weathering

C horizon
Bedrock

9.  Emergent Layer – a few
tree species grow very tall
and emerge up through
the canopy. These may
be 150 feet tall.
 The emergent layer is
made up of the tallest
trees that grow larger than
any of the other trees.

10. It is good to have your leaves in
the emergent layer because
there is lots of sunlight.

11.  Canopy Layer – tall
trees for this dense
layer that absorbs most
of the light energy. 80
to 100 feet tall. The
canopy layer is where
most of the leaves in a
tropical rainforest are
found.
 Very dense vegetation

12.  The canopy is very dense,
so it blocks out a lot of the
light.
The interlocking canopy

13.  Understory or Subcanopy
Layer – made of seedlings
that will grow to canopy if
light is available and a few
shade specialists.
 Shorter plants living in the
understory of the emergent
and canopy layers do not
get as much light so they
have to be able to grow in
the shade.

14. Only about 1% of the sunlight
reaches the understory level.
- Trees are smaller
– Their crowns are not thick
– Most have heights of between
5m and 15m

15.  Consists mainly of
ferns, shrubs and small
young trees.
 Covered by a carpet of
leaves.

16. •The forest floor is covered with dead leaves.
•These dead leaves will decompose (rot) and return the
nutrients that they contain to the soil.

17. The dominant vegetation in Tropical Rainforests is tall,
broadleaf, evergreen trees.
Broadleaf = leaves have flat, wide blades instead of needles.
Evergreen = trees maintain foliage (leaves) all year. Deciduous
trees, those that drop their leaves seasonally, do so as an
adaptation to cold conditions. In the tropics, there is no cold
season, therefore there is no need for trees to drop their leaves.

18.  Leaves
• Drip tips on the leaves
allow excess
water to drip off after a
downpour
• Leaves are large and
smooth with a thin cuticle
to facilitate transpiration
• Leaves, especially in the
upper canopy have a
strong petiole so that the
large raindrops do not
cause them to break off

19.  Lianas – are vines that
grow up trees to their
crown then between
the branches of
neighboring trees.
They “lace” the trees
together adding
support so they won’t
fall over since their
roots grow in very
shallow soil.

21.  Epiphytes – (epi = outer and phyte = plants) – are plants
that grow on other plants. By growing up off the forest
floor epiphytes have access to higher quality light (red and
blue).
 A diversity of plants have adapted to an epiphytic life.
There are epiphytic flowering
plants, mosses, cacti, ferns, and liverworts.

22.  Many of the trees are
covered with epiphytes.
The trunks are cloaked in
mosses. The large
epiphyte in the center is
a bromeliad. Large
bromeliads like this one
are called “tank
bromeliads” because
their cup of leaves holds
a lot of water. That water
is the drinking source for
arboreal animals.
Several species of frogs
lay their eggs in it and
the tadpoles develop in
the treetops.

24. Buttress roots are common on Tropical Rainforest Trees. They grow across the
surface of the thin rainforest soil. They work like kick stands to keep the tree from
tipping over. Also, because the soil is so nutrient poor, deep roots have no need to
grow deep. They’re more effective at the surface where they can absorb nutrients
from fallen leaves as they decompose.

25.  Slash and burn
 Fire
 Illegal Logging
 Agriculture- cash crop and ranching

26.  One of the most widely used methods to destroy
rainforests is using slash and burn agriculture.� With this
type of agriculture, all of the trees and plants in the
selected area are uprooted or cut down.� The downed
trees and flora are then burnt, so that all of the nutrients in
the plants are turned into ash, which is mixed with
soil.� After all of the vegetation has been burnt and the
ashes have been incorporated into the soil, people plant
crops.� The area of land that has been cleared in this
manner is only viable for a few years.� Once all of the
nutrients have been leached from the soil, the area is
abandoned and a new area of rainforest is selected to
undergo the same process.

27. This type of agriculture is problematic because�� �The huge
number of farmers who have descended upon the rainforests have
placed too much pressure on the land.� Not enough time is being
given to cleared patches for the forest to regenerate.� This �slash-
and-burn� farming has replaced traditional, sustainable�
cultivation in most tropical forests� (Lewis,1990, pg 60).� This is
very unfortunate because �slash-and-burn� agriculture is
responsible for the ruin of fifty acres of rainforest every hour�
(Gallant,1991, pg 4)

29.  During 1997 several fires broke out worldwide and as a
result, �More fires were recorded in that year than at any
time in history- millions of hectares of forest were
destroyed�� (Gay,2001, pg 32).
 In addition to fires that occur naturally, farmers and native
peoples use fire as a tool to clear land for
agriculture.� Cattle ranchers also use fire to clear the land
for their cattle,��The conversion of the rainforest into
grazing for cattle is a genuine ecological catastrophe.� The
replacement of the rainforest�s intricate structure by the
much simpler structure of pastureland is an intrinsically
negative process of biological simplification�
(Camarasa,2000, pg 292).

31.  Many government agencies are fighting illegal logging
to protect the forests. However, any type of logging
legal or illegal leads to deforestation. Trees are cut
down indiscriminately by logging companies, to fulfill
the demands of the wood market. This does not give a
chance to the local wildlife and trees to regenerate and
sustain themselves. Thus, leading to loss of wildlife
forever.
Read more at
Buzzle: http://www.buzzle.com/articles/causes-and-
effects-of-deforestation.html

33.  Undisturbed and logged rainforest areas are being
totally cleared to provide land for food crops, tree
plantations or for grazing cattle (Colchester &
Lohmann). Much of this produce is exported to rich
industrialised countries and in many cases, crops are
grown for export while the local populace goes hungry.
 Due to the delicate nature of rainforest soil and the
destructive nature of present day agricultural
practices, the productivity of cash crops grown on
rainforest soils declines rapidly after a few years.

34. Monoculture plantations - those that produce only one species of tree or one
type of food - on rainforest soil are examples of non-sustainable agriculture.
They are referred to as cash crops because the main reason for their planting is
to make money quickly, with little concern about the environmental damage
that they are causing.

35.  Cattle ranching has multiple negative effects to both the
environment and the people living in it.� For
example, cattle ranching �intensifies deforestation by
forcing peasant farmers into the rainforest to seek new
land to farm when they are evicted by ranchers who want
to convert their farmland to pasture�(Lewis,1990, pg 42).
 Cattle ranching is also negative because it� �causes the
land to decline in quality as the soil becomes depleted of
nutrients.� In fact, land cleared from rainforests generally
supports cattle for only three to seven years before it
deteriorates beyond recovery� (Lewis, 1990, pg 42).� Just
as the farmers do, the ranchers use the land until all the
nutrients are gone.� This makes it difficult for new flora to
grow back.

36.  One of the factors that allows cattle ranching to
destroy rainforests is that �rainforest ranchers have
relied on government subsidies and international
loans, which make cattle ranching artificially
profitable�Rainforest governments have also
supported cattle ranching with land giveaways, tax
breaks, and free technical assistance. Without this
support, rainforest ranching would lose much of its
appeal� (Lewis,1990, pg 43)

38. What is Deforestation?
 Deforestation is clearing Earth's forests on a massive
scale, often resulting in damage to the quality of the
land.

42. �
����Colchester and Lohmann (Ed), The struggle for Land and the Fate of the Forest,
1993, Zed Books, London.
Gallant, R. A. (1991). Earth's Vanishing Forests. New York: Macmillan� Publishing
Company.
Gay, K. (2001). Rainforests of the World (2 ed.). Santa Barbara: ABC-CLIO, Inc.
Josep M. Camarasa, R. F. (2000). Encyclopedia of the Biosphere (Vol. 2). Michigan: The
Gale Group.
Lewis, S. (1990). The Rainforest Book. Los Angeles: Living Planet Press.