rainforests. location of tropical rainforests tropical rainforests are found mostly within the...
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.
• 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.
• 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?
• 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=lay
• 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.
• 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.
• 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.
• The leaves are shaped to shed the heavy rainfall.
• 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
100-feet 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
• http://video.google.com.au/videoplay?docid=-2934374342545375813&q=planet+earth+jungles&ei=TnBESIuUMqHoqgOE-s3xCA&hl=en Planet Earth Jungle 48mins long
• Paradox – If rainforests are so luxuriant (green, have such big trees), why are their soils so poor?
• Nutrient Cycling, leaching.
Twigs and leaves fall to the ground and become ‘litter’
Decomposition (breaking down) of litter by termites, fungi and bacteria
Nutrients enter the soil
Soil is fertile
Leaching washesout soil nutrientsLeaching washesout soil nutrients
Broken Nutrient Cycle
Fill in the gaps on your own paper
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 fast-growing plants, they do not remain in the soil long, and remain close to the surface of the soil.
• Answer UTT Q1-6 p151. Use the heading Rainforest Ecosystems and Nutrient Recycling.