Major Biomes of the world


A large terrestrial ecosystem characterized by specific plant communities and formations; usually named after the predominant vegetation in the region. A brief description of the major terrestrial biomes is as follows:

The Tropical Rain Forests

It is a lush biome of tall broadleaf evergreen trees and diverse plants and animals. The dense canopy of leaves is usually arranged in three levels. The main characteristics of this biome are daylight for 12 hours, high insolation, average annual temperature of 25oC, and average annual precipitation about 200 cm. Plants and animals of this biome have great variety and diversity.

In the equatorial biome, ecological niches are distributed vertically rather than horizontally, because of the competition for light. The canopy is filled with a rich variety of plants and animals. Lianas (vines) stretch from tree to tree, entwining them with cords that can reach 20 cm in diameter. Epiphytes flourish there too: plants such as orchids, bromeliads, and ferns that live entirely above ground, supported physically but not nutritionally by the structures of other plants. Windless conditions on the forest floor make pollination difficult � insects, other animals, and self-pollination predominates. The upper level is not continuous but features tall trees whose high crowns rise above the middle canopy. The middle canopy is the most continuous, with its broad leaves blocking much of the light and creating a darkened forest or. The lower level is composed of seedlings, ferns, bamboo, leaving the litter-strewn ground level in deep shade.

In the equatorial biome, the smooth, slender trunks are covered with thin bark and buttressed by large, wall-like flanks that grow out from the trees to brace the trunks. These buttresses form angular open enclosures, a ready habitat for various animals. There are usually no branches for at least the lower two-thirds of the tree trunks.

The Amazon basin is the largest tract of tropical rain forest, also called selva. In addition, rain forests cover equatorial regions of Africa, Indonesia, Malabar coast and hilly tracts of North East India, the margins of Madagascar and South East Asia, the Pacific coast of Ecuador, Peru, Colombia, and the east coast of Central America. The cloud forest at high elevation in the Andes Mountain, remain perpetuated by high humidity and cloud cover. Undisturbed tracts of tropical rain forest are rare. The wood of many rain forest trees is extremely hard, heavy and dense � in fact, some species will not even at. The main varieties include ebony, mahogany and rosewood. Logging is difficult because individual species are widely scattered.

The animal and insect life of tropical rain forest is diverse, ranging from small decomposers (bacteria) to many animals living exclusively in the upper stories of the trees. These tree dwellers are referred to as arboreal, like sloths, monkeys, lemurs, parrots, beautiful birds, tree frogs, lizards, bats and snakes. Nearly half of the tropical forests have been cleared for cattle grazing, timber, fuel-wood and farming. The dominant trees require from 100 to 250 years to establish themselves after major disturbances.

2. Tropical Deciduous Forest

The tropical deciduous forests lose their leaves before the commencement of dry season. These forests are found on the margin of tropical rain forests. The main areas of deciduous forest include: Monsoon regions of India, Myanmar, Thailand, parts of Indonesia, Malaysia, Vietnam, Laos, Cambodia, Philippines, Angola, Zambia, Zimbabwe, Tanzania, Central America, parts of Brazil, Guyana and Venezuela. The tropical deciduous biome is coned to the monsoon regions where the average annual rainfall is generally between 100 to 200 cm. The rainfall occurs mainly during the rainy season. The average height of these forests is about 15 meters with no continuous canopy of leaves. Locally, they are known as caatinga of the Bahai State of north-east Brazil, the chaco area of Paraguay and Argentina, the brigalow scrub of Australia, and the dorneld of South Africa (Fig 2.1).

The trees of this biome are good for lumber, and valuable for cabinetry. Sagon (teak) sal, sheesum, mahuva, khair, bargad, peepal etc. are the important trees of this biome. Some of the trees with dry season adaptation produce usable waxes and gum, such as carnauba, and palm-hard waxes.

3. Tropical Savanna

It is one of the major biomes containing large expanses of grassland interrupted by trees and shrubs; a transitional area between the humid rain forests and tropical deciduous forests and the drier, semi-arid tropical grasslands and deserts. The savanna biome also includes treeless tracts of grasslands. The trees of the savanna grasslands are characteristically at- topped. Savannas covered more than 40 per cent of Earth�s land surface before human intervention but were especially modified by human caused fire. Fires occur annually throughout the savanna biome. Elephant grasses averaging five meters high is the typical vegetation of this biome. Savanna grasslands are much richer in humus than the wetter tropics and are better drained, thereby providing a better base for agriculture and grazing. Millets, sorghums, wheat, maize, fodder, pulses, oilseeds, and groundnuts (peanuts) are the common agricultural crops grown in this biome.

Savanna shrubs and trees are frequently xerophytic, or drought resistant, with various adaptations to protect them from the dryness. For example, the plants/trees are characterised by small thick leaves, rough bark, or waxy leaf surface. The largest area of savanna biome is in Africa (Sud an, Ethiopia, Kenya, Somalia, Tanzania etc.) including the famous Serengeti Plain and sahel region. The savanna grasslands are known as Llanos in Venezuela, Campo Cerrado in Brazil and Guiana, pantanal in southwestern Brazil.

Savanna biome is the home of large land-mammals that graze on savanna grasses or feed upon the grazers themselves. The main animals include: cheetah, zebra, giraffe, wild-buffalo, gazelle, wild-beast, antelope, rhinoceros, and elephant. Establishment of large tracts of savanna as biosphere reserves is critical for the preservation of this biome and its associated flora and fauna.

4. Mid-latitude Broadleaf and Mixed Forest

The mid-latitude broadleaf and mixed forest biome occurs along the Gulf of Mexico, Atlantic coastal plains, New England, and Great Lakes (North America), Northern China, North Korea, South Korea and Japan. The main species include red-pines, hemlock (evergreens), mixed with deciduous varieties of oak, beech, hickory, maple, elm, chestnut, etc.

These forests contain valuable timber, but their distribution has been greatly altered by human activities. In northern China, these forests have almost disappeared as a result of centuries of occupation. This deforestation, as elsewhere, was principally for agricultural purposes, as well as for building construction materials and fuel-wood.

5. Taiga and Montane (Needle-leaf) Forest

It is also called Taiga Biome. This biome stretches from Alaska to the eastern coast Canada, and the entire extent of Siberia, Russia to the European plain and Scandinavia. It is coned mainly to the Northern Hemisphere. The high altitudes of Himalayas, Andes, Alps, Rocky Mountains, etc. are also covered with the trees of this biome. However, mountain forests of needle-leaf trees exist worldwide at high elevation. The main trees include pine, spruce. Economically, these forests are important for lumbering, furniture, pulpwood and paper making.

6. Temperate Rain Forest

Known for lush green at middle and high latitudes, this biome occurs only along the narrow margins of the Pacific North-West in North America. This biome has few species of trees. The tallest trees in the world are found in this biome. The main species of tallest trees are redwoods (Sequoia sempervirens). These trees can exceed 1500 years of age and typically range in height from 60 to 90 m, with some exceeding 100 m. Virgin stands of other representative trees�Douglas fir, spruce, cedar, and hemlock have been reduced to a few remaining valleys in Oregon and Washington (U.S.A.), less than 10 per cent of the original forest and tough in their ability to withstand hot summer drought. The vegetation is called sclerophyllous (from sclera or �hard� and phyllos for �leaf�). It averages a meter or two in height and has deep, well-developed roots, leathery leaves, and uneven low branches. Mediterranean regions are important in commercial agriculture for subtropical citrus fruits, vegetables and nuts.

8. Mid-latitude Grasslands

Of all the natural biomes, the mid-latitude (temperate) grasslands are the most modified by human activity. This biome is also known as the �breadbasket� region of grain and livestock production of the world. In these regions, the only naturally occurring trees were deciduous broad-leafs along streams and other limited sites. These regions are called grasslands because of the original predominance of grass-like plants. The history of these plains is the history of grasslands.

These grasslands are known as Prairies in North America, Steppe in Eurasia, Pampas in Argentina and Uruguay, Veld in South Africa, and Down in Australia.

Written by princy

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