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On the basis of the homogeneity in soil, climate and vegetation, the following eight major Biomes of the world have been identified: 1. Tropical Rain Forest 2. Tropical Grassland 3. Deciduous Forest 4. Desert 5. Mediterranean Scrub Forest 6. Temperate Grassland 7. Taiga 8. Polar Tundra.
Biome # 1. Tropical Rain Forest:
This region extends from the equator to 10° N and 10° S latitudes. The region has wet equatorial climate with an annual average temperature close to 270°C. The annual variation of temperature is extremely small. The rainfall received by the region is heavy, more than 200 cm annually.
Therefore, the climate is very monotonous throughout the year. Because of heavy rainfall and high temperature, the region is full of luxuriant tree growth popularly known as rainforest, or selva. The forest is evergreen and the surface is covered with thick undergrowth.
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The region is the home for small forest animals and birds. Soil is lateritic and marshy and the humus content is very small because of the presence of bacteria. Stream flow tends to be continuous, leaches out all soluble constituents of the soil, and rotting and decay of the bedrock is found to be very deep.
Area:
The Amazon basin of Brazil in South America; the Congo river basin in Zaire, Africa; Malaysia and Indonesia fall under equatorial forests.
The Biome covers nearly 8 per cent of the earths’ surface and supports more than half of the total flora and fauna. The plants include broad leaf evergreen plants with distinct stratification of tall trees, climbers and undergrowths.
This biome is the home of more than 200 species of trees. The animals include monkeys, snakes, ant eaters, birds, bats, large carnivorous animals and fishes in the water bodies. Nearly 70-80 per cent of the known species of insects of the world is found in this Biome.
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The environment is such that people can meet their minimum needs with least effort. Infant mortality is very high. The region is infested with flies, insects, pests, mosquitoes and diseases. Due to hostile environment, natural resources still remain relatively unexploited.
Biome # 2. Tropical Grasslands:
Tropical grasslands extend on both sides of the equatorial zone upto 25°N latitudes in central and South America, Africa and Australia. In Asia, it extends upto 30° N latitude because of the continental air mass. Alternation of wet and dry seasons results in the growth of a distinctive coarse and tall grass with scattered trees. The areas enjoy hot summers (30°C) and warm winters (20°C). Annual rainfall varies from 25 cm to 100 cm. Soils of the region are mostly similar to those in the equatorial region.
Residual soils of the uplands are not fertile. But, the soil of the floodplains is highly productive. The region is full of carnivorous game animals, and a vast range of grazing animals. Many trees shed leaves in winter, many have thorns and hard leathery leaves.
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Area:
The tropical grasslands are known by different names in different parts of the world. They are called Llanos in Venezuela, Campos in Brazil, Savana in North Africa, and Veldt in South Africa.
The tropical grasslands of the world are identified as “Natural Cattle Countries”. The tropical climate allows tall coarse grass, which has led to cattle rearing.
In the Llanos of Venezuela, cattle are reared for meat, skin and hide. In dry season, there is shortage of water, and the cattle fall victim to pests and diseases. As such, cattle rearing is still in subsistence level and has not done well on commercial basis.
In the Campos of Brazil, cattle rearing is done on commercial basis and the region is a big exporter of meat, wool and skins. However, because of long dry season, the cattle are not of good quality.
In the Savanas of North Africa, cattle rearing is done on an extensive scale. The animals include cows, sheep and goats. Sheep and goats are reared mainly for skin and wool. The progress of the occupation is very slow because of the lack of good transport system leading to low demand, and because of pests and diseases.
In the Veldts of South Africa, cattle rearing is done by the white people. Cattle and sheep are also reared by some indigenous tribes. The famous marino wool comes from this region. There is no surplus of animal products for trade.
In Australia, tropical grasslands are found in areas where annual rainfall is between 50-100 cm. The beef cattle, goat and sheep are abundant. Large quantities of beef, wool and hides are produced in this region.
Biome # 3. Deciduous Forests:
Deciduous forests are found in temperate zone of north-central Europe, eastern Asia and eastern United States. The annual rainfall ranges from 75-150 cm. This region has different seasons. During winter season, the trees shed leaf and become leafless. The plants include Oak, birch, maple, hickory etc. and the major animals are deer, snakes, various birds, lizards, rabbits, bears, foxes etc.
Biome # 4. Desert:
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Deserts occur mainly on the western side of the continents along the tropic of Cancer and the tropic of Capricorn. The annual average temperature is around 38°C. The day temperature may rise to 50°C, and the night temperature may fall to 10°C. This causes high variation in the daily temperature. The rainfall is very scanty.
However, the short summer rain helps in growth of luxuriant grass. This provides plenty of food for grazing animals. Most parts of the desert are barren and full of sand dunes. Deserts are characterized by scanty of flora and fauna. The plants include different kinds of cacti, acacias and other succulents and animals include foxes, rabbits, cats, locusts, ants, lizards, snakes, scorpions, spiders and large number of insect eating birds.
Areas:
The main areas of tropical desert are in Africa and South America. Sahara, Kalahari and Atacama are desert areas of great extent. Arabia, Australia, Thar, Nabib and Lower California are also some of the important tropical deserts of the world. Most of the desert regions are either uninhabited, or the home of the nomades, except the irrigated areas of the Nile delta.
Biome # 5. The Mediterranean Scrub Forest:
The Mediterranean region is extensive around the sea by the same name. The most significant characteristics of the region is wet winter and dry summer. This has resulted in a unique natural vegetation of hard-leaved evergreen trees and shrubs. It is the home of broad leaved evergreen plants and drought resistant animals. Soils of the region cannot be put to simple classification. The annual average temperature varies from 8°C-28°C and average rainfall is below 15 cm.
Biome # 6. The Temperate Grassland:
The temperate grassland region is characterised by warm and dry summer, and cold winter. The summer temperature rises upto 24°C while the winter temperature is around 0°C. Annual rainfall varies from 30 cm to 60 cm, with maximum rain in summer. The region experiences two types of climates: semi-humid and semi-arid.
The vegetation consists mainly of short and tall grasses. The semi-humid grasslands are called prairies and the semi-arid grasslands are called steppes. The grasslands are suitable for grazing of cattle and sheep. Farming can be practised only with the help of irrigation. Soils of the steppe lands are generally deficient in humus. The soil contains calcium, which is especially suitable for gram crops.
Areas:
The main areas are Central North America, Eastern Europe, the erstwhile Soviet Union, Argentina, South Africa, parts of Australia and north China.
Biome # 7. Taiga:
The Taiga region extends from 55° N latitude to the Arctic circle. The region experiences short cool summer (10°C) and long cold winter (-40° C). The maximum range of temperature is around 60°C in Siberia, and is the highest in any part of the world. Precipitation is largely cyclonic in type, and is maximum in summer. Most of the precipitation is in the form of snowfall.
The region is full of needle leaf forest, often called boreal forest and woodlands called taiga. The soils are of podzol group, and not suitable for agriculture. The trees are small and more suitable for wood pulp than lumber. The ground is frozen.
Agriculture, having very short growing season, may be possible only during summer. The vegetation includes pine, fir, ceder, hemlock and spruce and the major animals are elks, deer, rabbits, pumas and many species of insects. Extensive areas are found in the former Soviet Union, Canada, Alaska and Scandinavia.
Biome # 8. Polar Tundra:
The polar tundra region occurs to the north of 60 °N latitude, with an east-west extension. The climate is characterised by extreme cold. The average temperature of the warmest month is between 0°C to 100°C and that of the coldest is around -180 °C. Total precipitation is less than 25 cm.
The range of temperature is much less than that in the coniferous forest region. The vegetation is of tundra type with grasses, sedges and lichens, but without trees except to the south. Tundra soils are mechanically formed, permanently frozen for permafrost condition, and very thin. Agriculture is practically non-existent. Reindeer, caribou, polar bear, beaver, fox and mink are the main animals of the region.
Area:
The polar tundra regions are found in the northern parts of Eurasia and North America. The people of northern Siberia are called the Yakuts and the residents of northern Canada and Alaska are known as Eskimos and Lapps.