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Old Friday, October 05, 2007
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Post Taiga and Rainforest ecosystem

Rain forest Ecosystem

The tropical rain forest can be found in three major geographical areas around the world.
Central America in the the Amazon river basin.
Africa - Zaire basin, with a small area in West Africa; also eastern Madagascar.
Indo-Malaysia - west coast of India, Assam, Southeast Asia, New Guinea and Queensland, Australia.

The tropical rain forest is a forest of tall trees in a region of year-round warmth. An average of 50 to 260 inches (125 to 660 cm.) of rain falls yearly.
Rain forests belong to the tropical wet climate group. The temperature in a rain forest rarely gets higher than 93 F (34 C) or drops below 68 F (20 C); average humidity is between 77 and 88%; rainfall is often more than 100 inches a year. There is usually a brief season of less rain. In monsoonal areas, there is a real dry season. Almost all rain forests lie near the equator.

Rainforests now cover less than 6% of Earth's land surface. Scientists estimate that more than half of all the world's plant and animal species live in tropical rain forests. Tropical rainforests produce 40% of Earth's oxygen.

A tropical rain forest has more kinds of trees than any other area in the world. Scientists have counted about 100 to 300 species in one 2 1/2-acre (1-hectare) area in South America. Seventy percent of the plants in the rainforest are trees.
About 1/4 of all the medicines we use come from rainforest plants. Curare comes from a tropical vine, and is used as an anesthetic and to relax muscles during surgery. Quinine, from the cinchona tree, is used to treat malaria. A person with lymphocytic leukemia has a 99% chance that the disease will go into remission because of the rosy periwinkle. More than 1,400 varieties of tropical plants are thought to be potential cures for cancer.

All tropical rain forests resemble one another in some ways. Many of the trees have straight trunks that don't branch out for 100 feet or more. There is no sense in growing branches below the canopy where there is little light. The majority of the trees have smooth, thin bark because there is no need to protect the them from water loss and freezing temperatures. It also makes it difficult for epiphytes and plant parasites to get a hold on the trunks. The bark of different species is so similar that it is difficult to identify a tree by its bark. Many trees can only be identified by their flowers.

Despite these differences, each of the three largest rainforests--the American, the African, and the Asian--has a different group of animal and plant species. Each rain forest has many species of monkeys, all of which differ from the species of the other two rain forests. In addition, different areas of the same rain forest may have different species. Many kinds of trees that grow in the mountains of the Amazon rain forest do not grow in the lowlands of that same forest.

Layers of the Rainforest

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.

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.

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.

Plant Life

Besides these four layers, a shrub/sapling layer receives about 3 % of the light that filters in through the canopies. These stunted trees are capable of a sudden growth surge when a gap in the canopy opens above them.

The air beneath the lower canopy is almost always humid. The trees themselves give off water through the pores (stomata) of their leaves. This process, called transpiration, can account for as much as half of the precipitation in the rain forest.

Rainforest plants have made many adaptations to their environment. With over 80 inches of rain per year, plants have made adaptations that helps them shed water off their leaves quickly so the branches don't get weighed down and break. Many plants have drip tips and grooved leaves, and some leaves have oily coatings to shed water. To absorb as much sunlight as possible on the dark understory, leaves are very large. Some trees have leaf stalks that turn with the movement of the sun so they always absorb the maximum amount of light. Leaves in the upper canopy are dark green, small and leathery to reduce water loss in the strong sunlight. Some trees will grow large leaves at the lower canopy level and small leaves in the upper canopy. Other plants grow in the upper canopy on larger trees to get sunlight. These are the epiphytes such as orchids and bromeliads. Many trees have buttress and stilt roots for extra support in the shallow, wet soil of the rainforests.

Over 2,500 species of vines grow in the rainforest. Lianas start off as small shrubs that grow on the forest floor. To reach the sunlight in the upper canopy it sends out tendrils to grab sapling trees. The liana and the tree grow towards the canopy together. The vines grow from one tree to another and make up 40% of the canopy leaves. The rattan vine has spikes on the underside of its leaves that point backwards to grab onto sapling trees. Other "strangler" vines will use trees as support and grow thicker and thicker as they reach the canopy, strangling its host tree. They look like trees whose centers have been hollowed out.

Dominant species do not exist in tropical rainforests. Lowland dipterocarp forest can consist of many different species of Dipterocarpaceae, but not all of the same species. Trees of the same species are very seldom found growing close together. This bio diversity and separation of the species prevents mass contamination and die-off from disease or insect infestation. Bio diversity also insures that there will be enough pollinators to take care of each species' needs. Animals depend on the staggered blooming and fruiting of rainforest plants to supply them with a year-round source of food.

Animal Life

Many species of animal life can be found in the rain forest. Common characteristics found among mammals and birds (and reptiles and amphibians, too) include adaptations to a life in the trees, such as the prehensile tails of New World monkeys. Other characteristics are bright colors and sharp patterns, loud vocalizations, and diets heavy on fruits.

Insects make up the largest single group of animals that live in tropical forests. They include brightly colored butterflies, mosquitoes, camouflaged stick insects, and huge colonies of ants.

The Amazon river basin rainforest contains a wider variety of plant and animal life than any other biome in the world. The second largest population of plant and animal life can be found in scattered locations and islands of Southeast Asia. The lowest variety can be found in Africa. There may be 40 to 100 different species in 2.5 acres ( 1 hectare) of a tropical rain forest.


A biome is the type of habitat in certain places, like mountain tops, deserts, and tropical forests, and is determined by the climate of the place. The taiga is the biome of the needleleaf forest. Living in the taiga is cold and lonely. Coldness and food shortages make things very difficult, mostly in the winter. Some of the animals in the taiga hibernate in the winter, some fly south if they can, while some just cooperate with the environment, which is very difficult. (Dillon Bartkus)
Taiga is the Russian word for forest and is the largest biome in the world. It stretches over Eurasia and North America. The taiga is located near the top of the world, just below the tundra biome. The winters in the taiga are very cold with only snowfall. The summers are warm, rainy, and humid. A lot of coniferous trees grow in the taiga. The taiga is also known as the boreal forest. Did you know that Boreal was the Greek goddess of the North Wind?

The taiga doesn't have as many plant and animal species as the tropical or the deciduous forest biomes. It does have millions of insects in the summertime. Birds migrate there every year to nest and feed.

Here is some information about the temperatures and weather in the taiga. The average temperature is below freezing for six months out of the year. The winter temperature range is -54 to -1 C (-65 to 30 F). The winters, as you can see, are really cold, with lots of snow.

Temperature range in the summer gets as low as -7 C (20 F). The high in summer can be 21 C (70 F). The summers are mostly warm, rainy and humid. They are also very short with about 50 to 100 frost free days. The total precipitation in a year is 30 - 85 cm (12 - 33 in) . The forms the precipitation comes in are rain, snow and dew. Most of the precipitation in the taiga falls as rain in the summer.

The main seasons in the taiga are winter and summer. The spring and autumn are so short, you hardly know they exist. It is either hot and humid or very cold in the taiga.

There are not a lot of species of plants in the taiga because of the harsh conditions. Not many plants can survive the extreme cold of the taiga winter. There are some lichens and mosses, but most plants are coniferous trees like pine, white spruce, hemlock and douglas fir.

Coniferous trees are also known as evergreens. They have long, thin waxy needles. The wax gives them some protection from freezing temperatures and from drying out. Evergreens don't loose their leaves in the winter like deciduous trees. They keep their needles all year long. This is so they can start photosynthesis as soon as the weather gets warm. The dark color of evergreen needles allows them to absorb heat from the sun and also helps them start photosynthesis early.

Evergreens in the taiga tend to be thin and grow close together. This gives them protection from the cold and wind. Evergreens also are usually shaped like an upside down cone to protects the branches from breaking under the weight of all that snow. The snow slides right off the slanted branches.

The taiga is susceptible to many wildfires. Trees have adapted by growing thick bark. The fires will burn away the upper canopy of the trees and let sunlight reach the ground. New plants will grow and provide food for animals that once could not live there because there were only evergreen trees.

Animals of the taiga tend to be predators like the lynx and members of the weasel family like wolverines, bobcat, minks and ermine. They hunt herbivores like snowshoe rabbits, red squirrels and voles. Red deer, elk, and moose can be found in regions of the taiga where more deciduous trees grow.

Many insect eating birds come to the taiga to breed. They leave when the breeding season is over. Seed eaters like finches and sparrows, and omnivorous birds like crows stay all year long.

Last edited by Xeric; Friday, May 15, 2009 at 07:29 PM.
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