Tropical Rainforests

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Tropical Rainforests

• Climate
• Distribution of Rainforest
• Structure of the Forest
• Plant adaptations
• Threats to the forest
• Useful products

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Distribution of Rainforests
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Climate

• The temperature averages 28-30C all year but
  gets warmer in March and September when the sun
  is not directly overhead and there is less cloud.
• There is a convectional storm almost every
  afternoon except in March and September when,
  because there is less sunshine, there is less
  evaporation so the atmosphere is not so full of
  moisture and there are fewer clouds.
• The climate is described as humid

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Structure of the Forest
There are 5 layers in the forest

• Emergents
• Canopy
• Under canopy
• Shrub layer
• Groundlayer

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Structure of the Rainforest
EMERGENT TREE
CANOPY
UNDER CANOPY
SHRUB LAYER
GROUND LAYER
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Plant adaptations 1. Emergents and 2. the Canopy

• Many plants have waxy leaves and drip tips to
  allow heavy rainfall to run off.
• The canopy and the emergents have buttress roots,
  to anchor the tree.
• Large leaves and dark green foliage to maximise
  photosynthesis.
• These emergent trees grow to over 40m as they try
  to gather the maximum amount of sunlight.
• The canopy forms a closed layer which allows
  little light through.
• There is a huge amount of growth in all layers
  every year.
• The increase in the Biomass is balanced by the
  amount of decay. This is Nutrient cycling. This
  can be shown in a Gersmehl Diagram. (see slide
  15)

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3. The under canopy

• In this layer plants have to be shade tolerant
  they have very big and very dark green leaves.
• There are often few branches on the tall,
  straight trunks.
• Flowers are very bright to attract insects the
  air is too still for wind pollination.
• There are sometimes parasitic plants living on
  the trunks of trees they get their food from the
  host tree.
• Many of the plants have valuable fruits such as
  Brazil nuts, bananas, mangoes, rubber

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4. The shrub Layer

• In this layer the shrubs are bushy and have many
  stems
• Shrubs have dark green leaves at the top of the
  plant
• The plants are shade tolerant
• They often have bright flowers which are strongly
  scented
• Tea, coffee and cocoa are crops that grow
  naturally in this layer

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5. Ground Layer

• It is very dark on the forest floor
• Ferns and orchids are common plants at this
  level. Some of the plants are parasitic.
• There are many gaps between plants but it is very
  difficult to get around due to the tangle of
  vines and dead, fallen branches. The Litter layer
  is quite thick but
• Plant and animal material decays quickly in the
  hot, humid conditions. This is the Litter layer.

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Threats to the Forest

• An area of forest the size of Belgium is clear
  felled for timber every year
• Local people have growing populations and need
  farmland
• Timber from the tall, straight trees is much
  sought after for building and for furniture
• Big business wants to extract resources from
  under the forest
• Hydro-electric schemes flood the forest
• Accidental fires burn out of control

Satellite image of deforestation in the Amazon
region, taken from the Brazilian state of Para on
July 15, 1986. The dark areas are forest, the
white is deforested areas, and the gray is
regrowth. The pattern of deforestation spreading
along roads is obvious in the lower half of the
image. Scattered larger clearings can be seen
near the center of the image.
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• Glossary
• Biomass Living and dead matter produced,
  including plants and animals. (Kg/m2/annum)
• Canopy The highest layer of the rainforest, made
  up of the tops of trees. Animals such as howler
  monkeys, red-eyed tree frogs, sloths and parrots
  live here.
• Equator An imaginary circle around the earth,
  equally distant at all points from the North and
  South poles. It divides the earth into two halves
  - the Northern and Southern Hemispheres.
• Emergent The tops of the tallest trees in a
  rainforest.
• Evaporate When moisture changes from liquid to
  gas in the air.
• Extraction To remove something (for example, to
  take out Brazil nuts from the Amazon rainforest).
  
• Forest Floor The ground layer, made up of tree
  roots, soil and decaying matter. Mushrooms,
  earthworms, and elephants all make their homes
  here.
• Greenhouse Effect The warming of the planet
  caused by chemicals which trap heat in the air.
  This process is being sped up by humans who put
  too many heat-trapping chemicals into the air.
  Some causes include car exhaust, factory smoke,
  and burning rainforests.
• Interdependence The concept that everything in
  nature is connected to each other, and cannot
  survive without the help of other plants, animals
  and abiotic factors (such as sun, soil, water and
  air) around it.
• Nutrients Food needed for growth by living
  things.
• Species A distinct kind of plant or animal that
  has many common characteristics or qualities.
• Sustainable Using products of the forest in a
  way that does not permanently destroy them, so
  that people in the future can also use them.
• Tropic of Cancer A circle around the earth,
  parallel and to the north of the equator.
• Tropic of Capricorn Similar to the Tropic of
  Cancer, but to the south of the equator.
• Understorey The second layer of rainforests,
  made up mostly of young trees and shrubs. Animals
  that live here include jaguars, tapirs, snakes,
  and woodpeckers.

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Additional Glossary

• Buttress roots wide spreading roots like
  scaffolding that support the very tall emergent
  and canopy trees.
• Climogram- a graph that shows temperature and
  rainfall on double axes. This is useful for
  describing climate and comparing the climate of
  two or more places.
• Convectional storm - rain that is the result of
  early evening cooling of moist air so that the
  vapour condenses and a short heavy storm happens
• Humid- the air is almost saturated with moisture
  and cooling a small amount will result in
  rainfall
• Nutrient Cycling the process of material
  dropping to the forest floor, decaying and the
  nutrients being added to the soil then being
  taken up by plants to make new growth.
• Parasitic- a plant or animal that lives on and
  gets its food from another species
• Photosynthesis- the biological process that uses
  sunlight, water and carbon dioxide to produce
  food for the plant and oxygen. The plants need to
  have Chlorophyll in their leaves for this to
  happen

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Useful Products
It is difficult to know how many useful products
come from the rainforest many species of plant
and animal have yet to be studied. However we do
know of many food crops such as coffee, cocoa,
tea, Brazil nuts, Oil palms, coconuts etc. that
are found in tropical forests and can be farmed
and harvested. Raw materials such as Copra,
Sisal, Hemp, Mahogony, Teak, Rubber are all
rainforest crops There are huge deposits of
useful minerals under the forest e.g. Iron ore,
Bauxite, Gold, Silver, Tin and Diamonds The high
rainfall and fast flowing rivers make Hydro
Electricity cheap once the dams and generators
have been installed. Many medicines such as
quinine for Malaria, Aspirin and several
anti-cancer drugs have been extracted from
Rainforest plants.
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Gersmehl Diagram for the Rainforest
Sunlight
Animal waste Decay
Harvest
Biomass
Leaf fall
Back to Emergents slide
Each circle represents a store of nutrients. Each
arrow represents a flow of nutrients. The size of
the circle is proportional to the volume of
nutrients stored. The width of the arrow is
proportional to the volume of nutrients flowing
along that route.
Litter
Nutrient Take up
Decay
Water
Soil
Weathered Rock
Erosion