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waterfall in jungle 


 Tropical Rain Forests

    The tropical rain forest biome is one of the most productive areas on earth. More than half of the different kinds animals and plants in the world live in the tropical rain forests. The abundant sunlight, warm temperatures, and daily rain lead to a fast turnover of nutrients, and plant growth is rapid.  This is a land without winter, so the growing season lasts all year. There are flowers and fruit all year round.

     These forests have been in existence for between 70 million and 100 million years, so this biome is very old. During this time the animals and plants have had the opportunity to adapt to each other very closely, and so there are many niches (roles in using a special part of the available resources) that unique organisms fill. Special insects pollinate special kinds of orchids, for instance.

     A hundred million years of rain also affects the soil. Looking at the plant life, it is easy to think that the soil is rich, but it is actually nutrient poor. Plants cannot grow on sunlight and rain alone: they need small quantities of minerals as well. These minerals include calcium, magnesium, and phosphorus. Over the years the rain has washed these out of the soil, so all the nutrients are actually in the living plants and animals.

    Competition for the minerals is fierce. If a leaf falls from a tall tree, or a piece of fruit is knocked off a branch, it may fall to the forest floor. Immediately the detritivores (bacteria and fungi that eat (break down) dead material) get to work and start digesting the fallen piece of organic matter. Their digestive processes make the minerals available again, and the net of shallow plant roots lies ready to soak them up and send them up into the trees and vines. This means that the nutrient "wealth" of the forest is all being used by the life forms living there. If the rain forest is cut down, nothing remains but a thin layer of low fertility soil.

     Rain forests consist of a number of layers.  Seen from above, the rain forest looks like a bumpy green carpet, but it actually has a number of levels.

The emergent layer has the tallest trees, which stand up individually above the trees crowded together below them. These trees get a lot of light, but they also have to deal with the wind. They make good perches for eagles and other predatory birds.

waterfall w stonesThe canopy consists of a thick growth of tall trees which capture much of the sunlight. Their branches touch, their leaves seem to fill every space where light may fall. Their branches bear colorful fruits. Epiphytes (plants that "grow in air") perch on the branches as well, and vines climb up from the forest floor to claim a share of the sun. Many of the animals live in the canopy, eating fruit, flowers, and leaves. Meat eaters go where the plant eaters are, and prey on the monkeys and colorful birds. Insects are everywhere. This part of the rain forest is filled with life.  It supports life forms and communities as the surface of the earth usually does.

The understory consists of small trees, shrubs, and bushes. These plants are adapted to low light levels, and their large, tender leaves capture as much light energy as they can. The shrubs support vines, mosses, and fragile amphibians, such a frogs, which enjoy the humid atmosphere.

The forest floor receives only about 2% of the light that falls onto the trees of the canopy. There are few plants down here in the twilight. The floor is littered with dead leaves, twigs, animals and fallen fruit, all of which are being digested by diligent insects and other detritivores. A few animals also live here, including wild pigs. They eat whatever has fallen from the rich communities above them. There is no underbrush for them to deal with, so travel in this dim world is easy.

Introduction to Rain Forests

  Tropical Rain Forests

 Temperate Rain Forests

 Tropical Rain Forest Food Web

 Temperate Rain Forest Food Web

 Tropical Rain Forest Food Pyramid

 Temperate Rain Forest Food Pyramid

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Copyright © 1999.   Elizabeth Anne Viau and her licensors.  All rights reserved. This material may be used by individuals for instructional purposes but not sold. Please inform the author if you use it at eviau@earthlink.net