CLASSIFICATION OF NATURAL VEGETATION

CLASSIFICATION OF NATURAL VEGETATION The natural vegetation of India is diverse owing to varied biotic conditions as well as unequal rainfall. A noteworthy clas­sification of Indian vegetation is that given by Champion and Seth who base it on three factors-temperature, altitude and rainfall. They have evolved eight broad types.

Tropical Evergreen or Rain Forests These are dense forests of luxuriant growth which look evergreen as their trees shed leaves at different times of the year. They are prevalent in areas where the annual rainfall is over 200 em and the average annual humidity exceeds 77 per cent. The annual temperature is 25°C to 27''<: on an average. Ma­hogany, bamboo, ivory wood, ebony, rubber trees are the economically significant trees of these forests. Such forests are found in the north-east. eastern regions of subtropical Himalaya (Terai), western portions of the Western Ghats and Andaman and Nicobar islands. The forests are divided as follows.

Tropical Wet Evergreell Forests They are found in areas where the annual rainfall is above 250 em. The many storeyed forests have an undergrowth of bamboos, ferns, canes and climbers. They contain economically valuable species such as ebony, rosewood, iron wood, champa, toon, etc. They occur in some of the north-eastern states, the Andaman and Nicobar islands and western parts of the Western Ghats.

Tropical Semi-Evergreell Forests Found in regions where the annual rainfall is below 200 em, these forests have evergreen trees mixed with deciduous ones. The mean annual temperature in these forests ranges from 24°C to 2rC and humidity is about 80 per cent. Trees have heavy barks and climbers, and buttressed trunks at many places. Important trees include champa, canes, ferns, orchids, rosewood, benteak, kadam, semul, laurel, etc. These forests occur in regions of upper Assam, lower eastern Himalaya, Orissa, and the Andaman and Nicobars.


Tropical Moist Deciduous Forests Also called the Monsoon forests, they occur where annual rainfall is 150 to 200 cm and the mean annual temperature is about 26­27°C. The forests are characterised by few species and the undergrowth is of canes and bamboos. Humidity varies from 60 to 80 per cent. They are found in the interior of the Indian Plateau and the Siwalik east of the Yamuna river. Sal, teak, tendu, sissoo, mahua, sandal, shisham are the important trees. Many of the trees are known for their valuable timber useful for constructional purposes and in furniture. The trees shed their leaves during spring and early summer.

Littoral or Swamp Forests Also called tidal forests, these occur in and around the tidal creeks and along the deltas of the rivers Ganga, Mahanadi, Krislma and Godavari. The trees, mainly evergreen, have profuse growth and stilt­like roots. The densest trees are found in the great Sunderban delta which has the sundari trees in ablmdance. Rhizophora and Nipa fruiticans (a type of palm) also grow in these forests. On the tropical tide-washed coasts where mud and silt have accumulated, dense mangrove forests flourish.

Dry Tropical Forests Such forests are mostly preva­lent in regions with an annual rainfall of 90 to 130 em, a mean annual temperature of 23 to 27"C and humidity ranging between 50 and 60 per cent. Their subtypes arc as follows.

Tropical Dry Deciduous Forests They run from the Himalayan foothills to Kanyakwmiri and comprise impor­tant trees -like bijasal, teak, tendu, amaltas, khair, palas, rosewood and axlewood. The tracts of these forests have a low canopy of grasses and shrubs in some places which has been cleared for agriculture or casuarina plantations.

Tropical TllOnt Forests These are mostly prevalent in those areas where rainfall is very low, i.e., 50 cm to 70 cm, the mean annual temperature is 25°C to 2rC and humidity is rather low, i.e., less than 47 per cent. Kutch, Saurashtra, Punjab, Haryana, Rajasthan, the Upper Ganga plains and the Deccan Plateau consist of such forests. Small trees such as khair, babul, thor, khejra, kanju, ak and neem are found in these forests.

Tropical Dry Evergreen Forests From Tamil Nadu to Nellore, such type of forests cover areas, where the mean rainfall is about 100 cm, the alillual temperature is 28°C and the mean annual humidity is 74 per cent. Trees are 12 m high with canopies. Bamboos are rare and the grass is not conspicuous. The important species of trees are khirni, jamun, kokko, toddy palm, casuarina, neem, cane, etc.
Riparian Forests They are common in wet places particularly along river banks and other wetlands where rainfall is less than 50 cm. Short trees and grasses such as munj and kans are abundant. Neem, shisham, pipal, babul, tamarind are common in such regions.

Subtropical Broad Leaved Hill Forests Such forests are common in the highlands of Bastar, Pachmari, Pal ani Hills, Khasi Hills on the lower slopes of the Himalaya in Assam and West Bengal. The mean annual temperature is about 18nC to 21°C, the mean annual, rainfall is about 75 to 125 cm and the humidity is 80 per cent. With an abundance of evergreen trees, these forests are called Shola forests in southern India.

Montane Wet Temperate Forests Generally at a height of 1800-3000 m above sea level especially in the hills of, Kerala, Tamil Nadu and the eastern Himalaya, the forests occur in regions with a mean annual temperature of about
11°C to 14"C and a mean annual rainfall of 150 to 300 cm.The important trees are oaks, magnolia, chilauni, birch, plum, michilus, deodar and hemlock.

Montane Moist Temperate Forests Such type of forests occur in the temperate eastern and western Himalaya, i.e., in Jammu and Kashmir, Himachal Pradesh, Punjab, Uttaranchal, Sikkim and Darjeeling. They are mainly com-, posed of coniferous species generally 30 to 50 m high and mosses and ferns that grow on trees. The important trees are pine, deodar, silver fir, oak, beach, rhododendrons, maple, etc.

Alpine Forests As the name suggests, these forests I cover the Alpine areas in the Himalayas, i.e" at a height of 2880 m to 3700 m. They constitute dwarf shrubs of juniper, fir, pine, birch and rhododendrons, On the south­em Himalayan slopes, the Alpine forests degenerate into a low evergreen scrub. On the northern slopes of the Himalaya, they represent a dry, xerophytic vegetation. I Grasslands Though the Indian grasslands are not I comparable to the savannah or steppe, they do occur on I wet soil ground and in the sal belt and some hilly areas,
They are sub-divided as follows,
Low-land Grasses Occurring in regions receiving 31 to 200 cm of rainfall where the temperature is high during summers, they are found in the plains of upper India­Punjab, Uttar Pradesh, Haryana, Bihar and north-west Assam. These grasses are found on many soil varieties and are suitable for cattle-breeding.

Upland or Hilly Grasses They are found at a height of over 1,000 m in the Himalaya and in the cleared forest areas of the Western Ghats in the Karnataka region. They are found among small tracts of Shola forests in South India.

Riverine Grasses Found in the northern part of India, they form the Bhabar pastures which are important grazing grounds for buffaloes and cattle.