Ecology And Environment
Amazonian rainforest

What are Rainforests



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Amazonian rainforest
Safa's image for:
"What are Rainforests"
Caption: Amazonian rainforest
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Image by: Shao
© public domain (Wikimedia commons) http://commons.wikimedia.org/wiki/File:Amazonian_rainforest.JPG

Forests that receive high amounts of annual rainfall and sunlight are described as rainforests. A special emphasis is given to rainforests as they play a vital role in maintaining global weather patterns. Rainforests are also important as the water evaporating from the trees in the forests cause rain in other areas.  Rainforests have a rich biodiversity, and they are home to millions of plant and animal species. There are two main types of rainforests: tropical and temperate.

Tropical Rainforests

Tropical rainforests are located near, or between, the Tropic of Cancer and Tropic of Capricorn, where the temperature approximates between 25 degrees Celsius and 30 degrees Celsius throughout the year. As they occur close to the equator, rainforests experience minimum variations in temperature. Tropical rainforests receive a high amount of rainfall (80 to 400 inches annually) and sunlight. These factors make the tropical rainforest the most productive and biologically diverse biome on Earth. Even though rainforests cover only about 6 percent of Earth’s total land area, it is estimated that they inhabit half of the world’s plant and animal species. Regions where tropical rainforests are found include, Central and South America, Africa, India, Southeast Asia and Australia.

Rainforests are characterized by lush vegetation, predominantly large, green leaved evergreen trees that live up to 50 to 100 years. Most of the animals and other organisms found in tropical rainforests are adapted to survive on trees. Plants called epiphytes often grow on the trunk of the trees. They are able to acquire moisture and nutrients while they are on the trunks and upper branches of the trees. Most animals are able to glide, fly or move from branch to branch without difficulty. Tropical rainforests are large and harbor numerous species of plants and animals at various heights of the forests. Therefore, rainforests are divided into layers or zones where different plant and animal communities inhabit.

Layers of the rainforest

The topmost layer, called the emergent layer, constitutes huge trees (emergents) that can grow up to heights of 150 to 200 meters. The emergents stand above the rest of the forest, shading the forest floor and creating a humid environment below the forest canopy. They receive more sunlight and less moisture, compared to other trees found in the forest. The emergent layer is home to unique animals, such as varieties of insects, bird species (example Harpy Eagles) and some species of bats.

Below the emergent layer, branches from emergent trees and treetops of tall trees that reach about 30 to 40 meters form a continuous canopy. Toucans, Parrots, Spider Monkeys and Orangutans are some of the animals that live in the canopy. Large, woody vines, such as lianas climb the trees in the canopy.

Found between the canopy and the forest floor is a layer of trees called the understory. This layer is much shaded by the canopy and receives the little sunlight that gets strained through the canopy. Trees that reside in the understory have large broad leaves to capture sunlight that reaches them. These trees shelter a large number of insects.

The bottom layer or the rainforest floor is dark and receives almost no sunlight. The forest floor is largely covered by decomposing leaves, branches and tree trunks that have fallen on the ground. The humid environment of this layer results in fast decomposition of vegetation, nutrients from which is mostly taken up by the living plants, leaving the top soil relatively infertile. Varieties of insects, and large animals, such as Jaguars and Bengal Tigers inhabit the forest floor.

Temperate rainforests

Temperate rainforests are in many ways similar to tropical rainforests. However, they are rare and much younger compared to tropical rainforests. Temperate rainforests occur along coastlines with temperate climates. They can be found along the coasts of several regions, including U.S Pacific coast, Canada, Europe, Russia and Eastern Asia. Temperatures in the temperate rainforests remain moderate, as temperate rainforests are located near seas, and receive moisture from the coastal fog. Temperate rainforests, similar to tropical rainforests, receive a great amount of rainfall (60 to 200 inches per year). Temperate rainforests also receive precipitation in the form of snow, especially if they are found at high altitudes. Temperate rainforests observe long, wet winters, and dry summers.

Most trees in temperate rainforests are evergreens, but unlike in tropical rainforests, coniferous trees such as redwoods, spruces, pines and firs that have needles rather than broad leaves, dominate. Temperate rainforests have all the layers found in tropical rainforests, except for the emergent (topmost) layer. Trees found in temperate rainforests are of few varieties (10 to 20 species) compared to tropical rainforests, which have hundreds of species of trees. Trees in temperate rainforests are huge and can grow as tall as up to 90 meters. They grow much older than the trees found in tropical rainforests. They harbor fewer species of epiphytes compared to the trees found in tropical rainforests. Mosses, lichens and ferns cover the tree trunks and forest floor.

The types of animals found in temperate rainforests differ from those found in tropical rainforests. Most of these animals are protected from rain and wind as they live close to, or near the ground. Temperate rainforests are inhabited by varieties of insects, birds and small mammals that eat the seeds that fall on the forest floor. Many species of insects live on the mosses and lichens, tree barks, and decomposing vegetation. Decomposition in the temperate rainforest is slower than in tropical rainforests as the environment is much cooler. Compared to the soil in tropical rainforests, temperate rainforest soils are more fertile. Deer, bobcats and cougars are some of the animals living in temperate rainforests.

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ARTICLE SOURCES AND CITATIONS
  • InfoBoxCallToAction ActionArrowhttp://kids.nceas.ucsb.edu/biomes/rainforest.html
  • InfoBoxCallToAction ActionArrowhttp://www.rainforestanimals.net/rainforest.html
  • InfoBoxCallToAction ActionArrowhttp://www.marietta.edu/~biol/biomes/temprain.htm