Current General Studies Magazine (December 2014)

General Studies - I: Geography Based Article (Tropical Forests)

Tropical Dry Evergreen Forests- Along the coasts of Tamil Nadu are areas which receive annual rainfall of about 100 cm mostly from the north-east monsoon winds in October-December. Here, the mean annual temperature is about 28°C and the mean humidity is about 75 per cent. These areas are covered by the tropical dry evergreen forests. The growth of evergreen forests in areas of such low rainfall arouses great botanical interest, and the reason for such a phenomena is difficult to explain. It may be due to the seasonal distribution of rainfall. Most of rainfall occurs in winter. The chief characteristics of these forests are short statured trees, upto 12 m high, with complete canopy, mostly of coriaceous leaved trees of short boles, no canopy layer differentiation, bamboos are rare or absent and grasses not conspicuous. The important species are khirni, jamun, kokko, ritha, tamarind, neem, machkund, toddypalm, gamari canes, etc. Most of the land under these forests has been cleared for agriculture or casuarina plantations.

Tropical Dry Deciduous Forests- These are similar to moist deciduous forests and shed their leaves in dry season. The major difference is that the species of dry deciduous forests can grow in areas of comparatively less rainfall of 100-150 cm per annum. They represent a transitional type; on the wetter side, they give way to moist deciduous and on the drier side they degenerate into thorn forests. Such forests are characterised by closed and rather uneven canopy, composed of a mixture of a few species of deciduous trees, rising upto a height of 20 metres or so. Enough light reaches the ground to permit the growth of grass and climbers. Bamboos also grow but they are not luxuriant.

The tropical dry deciduous forests are widely distributed over a large area. They occur in an irregular wide strip running north-south from the foot of the Himalayas to Kanniyakumari except in Rajasthan, Western Ghats and West Bengal. The important species are teak, axlewood, tendu, bijasal, rosewood, amaltas, palas, haldu, kasi, bel, lendi, common bamboo, red sanders, anjair, harra, laurel, satinwood, papra, achar, sal, khair, ghont, etc.

Large tracts of this forest have been cleared for agricultural purposes and these forests have suffered from severe biotic factors such as over cutting, over grazing and fire, etc.

Tropical Thorn Forests- In areas of low rainfall (less than 75 cm), low humidity (less than 50 per cent) and high temperature (25°-30°C), there is not much scope for thick forests and only tropical thorn forests are found. The trees are low (6 to 10 metres maximum) and widely scattered. Acacias are very prominent, widely and pretty evenly spaced. Euphorbias are also conspicuous. The Indian wild date is common, especially in damper depressions. Some grasses also grow in the rainy season.

These forests are found in the north-western parts of the country including Rajasthan, south­western Panjab, western Haryana, Kuchchh and neighbouring parts of Saurashtra. Here they degenerate into desert type in the Thar desert. Such forests also grow on the leeside of the Western Ghats covering large areas of Maharashtra, Karnataka, Andhra Pradesh and Tamil Nadu. The important species are khair, reunjha, neem, babul, thor, cactii, khejra, kanju, palas, ak, nirmali, dhaman, etc.

Question:-

1. Write an essay on tropical forests in India.

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