РефератыИностранный языкJuJungles And Rain Forests Essay Research Paper

Jungles And Rain Forests Essay Research Paper

Jungles And Rain Forests Essay, Research Paper


Jungle and rain forest are terms that are often used synonymously but with


little precision. The more meaningful and restrictive of these terms is


rain forest, which refers to the climax or primary forest in regions with


high rainfall (greater than 1.8 m/70 in per year), chiefly but not


exclusively found in the tropics. Rain forests are significant for their


valuable timber resources, and in the tropics they afford sites for


commercial crops such as rubber, tea, coffee, bananas, and sugarcane. They


also include some of the last remaining areas of the Earth that are both


unexploited economically and inadequately known scientifically.


The term jungle originally referred to the tangled, brushy vegetation of


lowlands in India, but it has come to be used for any type of tropical


forest or woodland. The word is more meaningful if limited to the dense,


scrubby vegetation that develops when primary rain forest has been degraded


by destructive forms of logging or by cultivation followed by abandonment.


Types of Rain Forest


Rain forests may be grouped into two major types: tropical and temperate.


Tropical rain forest is characterized by broadleaf evergreen trees forming


a closed canopy, an abundance of vines and epiphytes (plants growing on the


trees), a relatively open forest floor, and a very large number of species


of both plant and animal life. The largest trees have buttressed trunks and


emerge above the continuous canopy, while smaller trees commonly form a


layer of more shade-tolerant species beneath the upper canopy. The maximum


height of the upper canopy of tropical rain forests is generally about 30


to 50 m (100 to 165 ft), with some individual trees rising as high as 60 m


(200 ft) above the forest floor.


The largest areas of tropical rain forest are in the Amazon basin of South


America, in the Congo basin and other lowland equatorial regions of Africa,


and on both the mainland and the islands off Southeast Asia, where they are


especially abundant on Sumatra and New Guinea. Small areas are found in


Central America and along the Queensland coast of Australia.


Temperate rain forests, growing in higher-latitude regions having wet,


maritime climates, are less extensive than those of the tropics but include


some of the most valuable timber in the world. Notable forests in this


category are those on the northwest coast of North America, in southern


Chile, in Tasmania, and in parts of southeastern

Australia and New Zealand.


These forests contain trees that may exceed in height those of tropical


rain forests, but there is less diversity of species. Conifers such as


REDWOOD and Sitka spruce tend to predominate in North America, while their


counterparts in the southern hemisphere include various species of


EUCALYPTUS, Araucaria, and Nothofagus (Antarctic beech).


Ecology


Rain forests cover less than six percent of the Earth’s total land surface,


but they are the home for up to three-fourths of all known species of


plants and animals; undoubtedly they also contain many more species as yet


undiscovered. Recent studies suggest that this great diversity of species


is related to the apparently dynamic and unstable nature of rain forests


over geologic time. The fact is that despite their appearance of fertile


abundance, rain forests are fragile ecosystems. Their soils can quickly


lose the ability to support most forms of vegetation once the forest cover


is removed, and some soils even turn into hard LATERITE clay. The effect of


forest removal on local climates is also often profound, although the role


of rain forests in world climatic changes is not yet clear.


Humans and Rain Forests


Throughout history, human beings have encroached on rain forests for living


space, timber, and agricultural purposes. In vast portions of upland


tropical forest, for example, the practice of “shifting cultivation” has


caused deterioration of the primary forest. In this primitive system of


agriculture, trees are killed in small plots that are cropped for two or


three seasons and then abandoned; if the plots are again cultivated before


primary vegetation has reestablished itself, the result is a progressive


deterioration of the forest, leading to coarse grass or jungle. Lowland


forests are similarly being reduced in many areas; on the island of Java,


the lowland primary forest has been almost totally removed and replaced


with rice fields or plantation crops such as rubber. In the 20th century


these incursions on rain forests have grown rapidly, and numerous


organizations are now attempting to reduce the rate of the loss.


Bibliography: Caufield, Catherine, In the Rainforest (1985); Forsyth,


Adrian, and Miyata, Ken, Tropical Nature: Life and Death in the Rain


Forests of Central and South America (1984); Sutton, S. L., et al.,


Tropical Rain Forest: Ecology and Management (1984); Whitmore, T. C.,


Tropical Rain Forests of the Far East, 2d. ed. (1984).

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