Transcript document

Rainforests
Location of Tropical Rainforests
• Tropical rainforests are found mostly
within the tropics of Cancer and
Capricorn (between 23½° North and
23½° South of the equator). These
regions are wet and warm, which are the
essential qualities of tropical
rainforests. Rainforests can be found
in Central America, Africa, Southern
Asia and Australasia.
Ecosystems
• A community of interacting plants and
animals.
What is a biome?
• A biome is a very large ecosystem e.g. Tropical
Rainforest. The map below shows 9 of the world's
main biomes. http://geoggers.x10hosting.com/dme/Climates%20&%20biomes%20(2).swf
A tropical rainforest is a type of biome found in hot, humid
environments in equatorial climates. They contain the most diverse
range and highest volume of plant and animal life found anywhere
on earth.
Climate
• In general, tropical rainforests have hot
and humid climates, where it rains
virtually everyday. At some parts of the
year the rainfall is extremely heavy,
while in other parts of the year it will
rain a lot less. Temperatures vary
through the year - but much less than
the rainfall.
The graphic shows average rainfall and temperature in Manaus, Brazil, in
the Amazon rainforest. Total rainfall is 2104mm per year, most of it during
the rainy season from December to May. Notice how much the rainfall
varies over the year: the highest monthly rainfall is in March with over
300mm, while the lowest is in August with less than 50mm. Meanwhile the
temperature only varies by 2°C.
Why does it rain so much in the rainforest?
Convectional rain
Questions
• Answer UTT Q1-6 p146. Use the
heading Where are the Rainforests
located?
Rainforest vegetation levels
•
•
http://www.rainforestlive.org.uk/index.cfm?articleid=366&articleaction=layerga
me Game
Tropical rainforests have dense vegetation, which typically occurs in four levels.
From ground level up these levels of vegetation are:
•
The Shrub layer or Forest floor is at ground level in a tropical forest. It is
dark and gloomy with very little vegetation between the trees. During heavier
rainfalls this area can get flooded.
•
Under canopy is the second level up. There is limited sunlight. Saplings wait here
for larger plants and trees to die, leaving a gap in the canopy into which they can
grow. Woody climbers called lianas avoid having to wait for gaps by rooting in the
ground and climbing up trees to get to the sunlight.
•
Canopy is where the upper parts of most of the trees are found. The canopy is
typically about 65 to 130 feet (20 to 40 metres) tall. This leafy environment is
full of life such as insects, arachnids, birds and some mammals.
•
Emergents are the tops of the tallest trees in the rainforest. These are much
higher, and give the trees an advantage (in terms of light) than the average
trees that populate the forest canopy.
http://www.pbs.org/wnet/nature/fun/deepjungle_flash.html interactive layers
for personal use only
•
The graphic shows the different levels of rainforest vegetation,
and the relative amount of sunlight each one receives.
Plant Adaptations
• Each of these plants is adapted to
rainforest conditions in a different way.
• Fan palms have large, fan-shaped leaves
that are good for catching sunshine and
water. The leaves are segmented, which
allows excess water to drain away.
Lianas
• These are thick vines that loop around tree
trunks to make their way up to the canopy and
the sunlight. They have thick, woody stems
and come in various lengths (up to 3,000 ft)
and varying shapes. They begin life on the
forest floor but depend on trees for support
as they climb upwards towards the sunlight
they need for survival. They do this by
attaching themselves to trees with sucker
roots or tendrils and growing with the young
sapling, or they climb by winding themselves
round the tree's trunk.
• When they reach the top of the canopy they
often spread to other trees or wrap
themselves around other lianas. This network
of vines gives support against strong winds to
the shallow-rooted, top-heavy trees.
However, when one tree falls several others
may be pulled down also.
Lianas include rattan palms, philodendron and
Strychnos toxifera (from which the deadly
poison strychnine is obtained). Rattans, the
Asian lianas, have thorny stems and can reach
heights of 650 feet (200 m). They are used
to make a variety of things including baskets,
ropes and wicker furniture.
Epiphytes
• These plants forget about roots in the soil they perch high up on branches.
Epiphytes grow everywhere but can be found
mainly on the branches, trunks, and even the
leaves of trees. The name 'epiphyte' comes
from the Greek word 'epi' meaning 'upon' and
'phyton' meaning 'plant'.
Different types of epiphytes may grow on the
same tree, including orchids, cacti,
bromeliads, aroids, lichens, mosses and ferns.
They begin their life in the canopy from seeds
or spores transported there by birds or
winds.
Strangler Figs
• Most stranglers are members of the fig family. In
Spanish they are known as matapalo - 'killer tree'.
The seed of the strangler fig starts life as an
epiphyte high in the trees, borne by birds and
monkeys which eat the fig fruit. The seedling fig
sends down long roots to the ground from where it
begins to surround the host tree. It grows quickly and
eventually suffocates the host: when the host tree
dies it leaves an enormous upright strangler with a
hollow core.
By using an adult tree as its host, the strangler fig
avoids competition for light and nutrients at ground
level.
Buttress Roots
• Above-ground root system to ensure
stability for the tallest trees and to
increase the surface area over which
the plant can draw its nutrients.
Drip Tips
• The leaves are shaped to shed the
heavy rainfall.
Vegetation
• After millions of
years of growth, the
vegetation in the
rainforest forms
four main layers
• Soil is poor, so plant
roots grow close to
surface to utilise
the nutrients
• Tallest trees have
buttress roots to
stop them toppling
over
Answer UTT Q 1-7
p147 of your text. Use
the heading
Plant Adaptations
Animal Adaptations
• Parasol Ants (forest floor)
• Leaf-cutter, or parasol ants, climb trees up to 100feet tall and cut out small pieces of leaves. They then
carry these fragments, weighing as much as 50 times
their body weight, back to their homes. Sometimes
they must travel 200 feet, equal to an average human
walking about 6 miles with 5,000 lbs. on his/her back!
Parasol Ants (forest floor)
• These ants do not eat the leaves they
have collected, but instead bury them
underground. The combination of leaves
and substances that the ants produce
such as saliva allows a type of fungus to
grow. This fungus is the only food that
the ants need to eat.
The Jaguar (forest floor and understorey)
• The Jaguar is both a good climber and a good
swimmer. It pounces from trees on its prey, and is at
home both in the understorey and on the forest floor.
Toucans and Parrots (canopy)
• Toucans and Parrots have large beaks. These beaks
give them a great advantage over other birds with
smaller beaks. The fruits and nuts from many trees
have evolved with a tough shell to protect them from
predators. In turn toucans and parrots developed
large strong beaks, which serves as a nutcracker and
provides them with many tasty meals.
The three-toed sloth (canopy)
• The three-toed sloth is born with brown fur, but you
would never know this by looking at it. The green
algae that makes its home in the sloth's fur helps it
to blend in with the tops of the trees, the canopy,
where it makes its home. But green algae is not the
only thing living in a sloth's fur; it is literally "bugged"
with a variety of insects. 978 beetles were once
found living on one sloth!
The Woolly Spider Monkey (canopy)
• The spider monkey is a wonderful acrobat which can
leap six metres from tree to tree. It has a special tail
that can be used like a hand to hang from trees or to
reach out for fruit (this is called a prehensile tail).
Answer UTT Q1-8
P 149. Use the
heading Animal
Adaptations
Video
• http://video.google.com.au/videoplay?docid=2934374342545375813&q=planet+earth+jungles&ei=TnBESIuU
MqHoqgOE-s3xCA&hl=en Planet Earth Jungle 48mins long
Rainforest Soils
• Paradox – If rainforests are so
luxuriant (green, have such big trees),
why are their soils so poor?
• Nutrient Cycling, leaching.
Dense
vegetation
Soil is fertile
Nutrient
Cycle
Nutrients enter
the soil
Twigs and leaves
fall to the ground
and become ‘litter’
Decomposition (breaking
down) of litter by termites,
fungi and bacteria
Leaching washes
out soil nutrients
Fill in the gaps on your own paper
Deforestation
Less
vegetation
Broken
Nutrient Cycle
Rainforest water and nutrient
cycles
• Rainforest ecosystems are
characterised by heavy convectional
rainfall, high humidity and lushness of
vegetation, and nutrient-rich but
shallow soil. These factors give rise to a
unique water cycle and nutrient cycle.
Rainforest water cycle
• The rainforest climate is very humid. The
vegetation is very lush as water is taken up by
the roots and rain is intercepted as it falls much of it at the canopy level. The next day,
as the rainforest heats up, the water given
off by the plants and trees evaporates into
the atmosphere - where it forms into clouds
to make the next day's rain. This is called
convectional rainfall.
Rainforest nutrient cycle
• Plenty of dead plant material and the
hot, damp conditions on the forest floor
allow rapid decomposition. This provides
plentiful nutrients that are easily
absorbed by plant roots. But because
these nutrients are in very high demand
from the rainforest's many fastgrowing plants, they do not remain in
the soil long, and remain close to the
surface of the soil.
Questions
• Answer UTT Q1-6 p151. Use the heading
Rainforest Ecosystems and Nutrient
Recycling.