Natural Vegetation

Vegetation consists of those plants & trees which grow together in mutual association with each other under the influence of climate & soil. The climate is affected by the relief  & therefore there is a close relationship between relief, climate and vegetation. It is also modified by human activities.

All types of vegetation other than cultivated fields are commonly referred to as “forests”, irrespective of the nature of plants that grow in the region.

The Forest cover includes all lands which have a tree canopy density of more than ten percent when projected vertically on the horizontal ground, with a minimum areal extent of one hectare. The forest cover reported in Indian State Forest Report. Does not make any distinction between the origin of tree crops (whether natural or man-made) or tree species; and encompasses all types of lands irrespective of their ownership, land use and legal status. Thus, all the tree species along with bamboos, fruit bearing trees, coconut, palm trees, etc. and all the areas including forests, private, community or institutional lands meeting the above defined criteria, have been termed as forest cover.

The assessment of forest cover of the entire country is carried out at an interval of two years by interpretation of satellite data. However, broadly speaking the natural vegetation of Indian may be classified broadly into the following  types:-

The Tropical Evergreen Forests or Tropical Evergreen Rain Forests

There forests are found in hot and humid areas of India. The average annual rainfall in these areas is above 200 cms and the relative humidity is more than 70%. The average temperature is around 24^oC.

The trees are evergreen as there is no period of drought. Though the heavy rain is experienced only during the rainy season, the soil retains enough moisture for the rest of the year. Trees are tall, above 60 metres high & yield valuable hard wood. Heavy rain & high temperatures encourage luxuriant growth of trees, climbers, epiphytes, bamboos & ferns. Leaves are broad to give out excess moisture by evapo-transpiration, to increase surface area, to receive more sunlight and manufacture more food. There is dense undergrowth. These forests are spread over 4.6 million hectares in Andaman & Nicobar Islands, Assam, Meghalaya, Nagaland, Manipur, Mizoram, Tripura, West Bengal & on the Western slopes of the Western Ghats.

The economically useful species are rosewood, mahogany, ebony, shisem, toor & bamboos.

Tropical Monsoon Deciduous Forests

Areas receiving 100 to 200 cms of annual rainfall & having a distinct dry season are covered by tropical monsoon deciduous forests. These trees shed their leaves during the dry period usually from March to May to prevent loss of moisture through evapo-transpiration as also to reduce surface area.

These forests grow over the Sahayadris, the north-eastern parts of the peninsula, middle & lower Ganga Valley and along the foothills of the Himalayas in the Shiwalik, the bhabar & the terai.

These forests are commercially very important for building purposes & furniture making. The principal trees of these species are teak, sal, sandalwood, mango, khairm, mahua, bamboo, semal, myrobalan, arjanand & the banyan tree. There are 30 to 45 metres tall & cover about 20% of our forest area.

Tropical Dry

Areas receiving 50 cms to 100 cms of annual rainfall are covered by tropical dry forests. Main trees are neem, Shisham, Bakul & Pipal. These trees shed their leaves with the advance of summer season. These are less dense & small in size than the trees of monsoon forests. Their normal height is 6 to 9 metres. Their roots are thick & long so that they can use the underground water in the best possible manner. They have thick bark to avoid undue evaporation. Most of these forests have been cleaned for cultivation. Presently they cover just 5.2 million hectares of land.

Semi-desert & desert vegetation

This type of vegetation is found where the rainfall is below 25 cm and temperature is 25^oC to 27^oC. Consequently xerophytic type of vegetation is found in West Rajasthan, Sind, Kachchh & Saurashtra in Gujarat, the drier parts of Southern Punjab and the dry, rain-shadow areas of the Deccan Plateau. The Ladakh region & the Middle & Lower Basin of Indus are also characterized by sparse vegetation. The vegetation is characterized by thorny bushes growing apart from each other. The plants have deep roots, to tap water from great depths, thick fleshy stems to store water so as to survive during the long drought, absence of leaves to reduce transpiration from the surface area & waxy leaves to close the pores.

The main species are thorny bushes, wild berries, cacti, kikar & babul (acacias).

The Mountain Forests

These are mixed forests of deciduous and coniferous type, depending on elevation & rainfall. They usually grow at an altitude of 1500 m on the hills of southern India and at an altitude of 1000 m in the Himalayas.

On the slopes of the Eastern Himalayas we find broad-leaved evergreen trees growing e.g. oak. At the higher altitude of the Himalayas, bushes, shrubs and thickets of grow. Beyond 6,000 m only snow is found.

Where temperatures are cooler and rainfall low, coniferous forests flourish. Trees are conical in shape so that snow can slide. They are evergreen because of less rain and lower temperature. Needle shaped leaves reduce transpiration, low seasonal rain supports tree growth, while they have more wood than leaves, as the wood stores the food. There is little undergrowth due to less rain, low temperature & there is no simultaneous falling of leaves.

The main species are spruce, cedar, silver fir, pine deodar, magnolia and laurel.

The Tidal Forests

Along the edges of the deltas of the rivers Ganga, Mahanadi, Godavari & Krishna, Mangrove, Tidal or Littoral Forests flourish due to the flooding of these areas by the sea during high tide. These lowlands have thick deposits of mud & silt of saline water during high tide. Some of these forests are dense and impenetrable.

Mangrove forests are well-developed in the tidal zone of the Ganga delta in West Bengal &Bangladesh where they are known as Sunder bans from the Sundri trees which grow in abundance. In this area the casuarina tree is also found. The mangrove tree has stilt like supporting roots which are exposed at low tide. Gorjanand Hintal are other species found in these swamps. The wood is hard & durable & used for boat building and fuel.

Plants and Forests

India is well known not only for the diversities of its physiography and socio-economic structure, but also for the sharp contrasts in the growth of plants and forests. Both, plants and forests can be man-made as well as natural. The significance of planted trees and forests is in no way less than the natural vegetation. In fact, in many areas, where natural forests have been cut down on a massive scale, the environment has changed considerably and the areas are facing the problems of soil erosion and decline in rainfall. The Government of India is, therefore, seriously tackling this problem and large scale planting of trees not only in the upper areas of the rivers to check the soil erosion but also in the urban centres is being taken up to develop a healthy environment. Plantation of suitable vegetation in Rajasthan has helped in reducing the deserted landscape.

FORESTS

In terms of land ecology, Indian forest cover is inadequate. Most states have less than 30 per cent of their total area under forest while Punjab, Haryana, Rajasthan and Gujarat have even less than 10 per cent each.

Only Manipur, Tripura, Arunachal Pradesh, Sikkim and the Andaman & Nicobar Islands have substantial areas under forest.

The reasons for lack of forest cover in many parts of the country are several. In the case of Rajasthan, Punjab, Haryana and Gujarat, it is the absence of rainfall. In the case of Punjab and Haryana, however, the situation is accentuated by land being increasingly brought under the plough (in northern Punjab, the forests along foot-hills have vanished due to deforestation and cultivation). This is a condition found in West Bengal. Uttar Pradesh and Bihar too, where the natural vegetation has been almost completely replaced by cultivated area. And this despite the rather copious rainfall enjoyed by West Bengal and Bihar. The forest areas in these states are generally confirmed to the low hilly slopes in the north.

The low per cent of forest area in Jammu & Kashmir is due to a number of reasons, the important ones being low rainfall, steep barren slopes and snow-covered peaks. Maharashtra, Karnataka, Andhra Pradesh and Tamil Nadu also suffer from lack of forest cover, mainly due to the rain-shadow effect (which makes the Deccan Plateau semi-arid). Along the coastal areas of Andhra Pradesh and Tamil Nadu, where the rainfall is substantial, the forests have been cleared to bring the land under cultivation.

A major problem India will have to face in the near future is the dearth of wood for both industrial and domestic purposes (fuel, construction etc.). Such a dearth ushers in another major danger as well: the possibility of an overall drop in rainfall. This has already been experienced in the Nilgiris in South India where the indiscriminate falling of forests has resulted in a drop in rainfall and, when the rains do come there is an increase in landslides. Absence of vegetation cover in most of India has already reduced the soil cover and hence the percolation of water.

Government is the largest timber producing agency in the country. The total production of wood is estimated at 21.5 million cubic metres, of which 7.6 million cubic metres constitute  industrial wood and the rest fuel wood.

India is by far the largest producer of hardwood in the world (203.1 million cubic metres). On the other hand, India produces 17.5 m cum of the world’s 437 m cu of industrial hardwood a year.

Over 16 per cent of the total forest are[2]a in India is inaccessible and 45 per cent of this area could yield timber and other forest produce. Forests in India may be broadly classified into four major groups: tropical, sub-tropical, temperate and alpine. Each of these may be further divided into forest types.