Geography · Ch 5 — Natural Vegetation
Types of Forests
Types of Forests
The map is a choropleth of India, drawn with a graticule of latitude and longitude lines, and it divides the country into five shaded vegetation zones. A legend in one corner lists the five types: Littoral and Swamp Forest, Montane Forest, Tropical Thorn Forest, Tropical Deciduous Forests, and Tropical Evergreen and Semi Evergreen Forests. A scale bar running 0–600 km lets you measure distances across the country.
Reading the shading, the pattern tells the story of how rainfall and altitude shape vegetation. Tropical Evergreen and Semi Evergreen Forests hug the western slope of the Western Ghats, the hills of the northeast, and the Andaman and Nicobar Islands — the wettest, warmest corners of India. The Tropical Deciduous Forests, the most widespread type, blanket a vast central belt across the peninsula and the northern plains, reflecting the 70–200 cm rainfall zone that dominates the country. Tropical Thorn Forest appears as a drier patch over Rajasthan, Gujarat, and the Deccan interior, where rainfall drops below 50 cm. The Montane Forest follows the entire Himalayan arc, a long band that climbs through successive vegetation zones with altitude. Littoral and Swamp Forest shows up as small coastal patches, most visibly at the Sunderbans and along other deltaic coasts. …
The Big Picture
The natural vegetation of India is not a uniform green blanket. It changes with rainfall, temperature, altitude, and soil. The book classifies Indian forests into five broad types: tropical evergreen and semi-evergreen, tropical deciduous, tropical thorn, montane, and littoral and swamp forests. Each type is tied to a specific climate, and once you understand the rainfall and temperature that drives each one, the distribution of forests across the map starts to make sense.
Tropical Evergreen and Semi-Evergreen Forests
These forests grow where it is warm and humid all year, with annual precipitation above 200 cm and mean annual temperature above 22°C. You find them on the western slopes of the Western Ghats, the hills of the northeastern region, and the Andaman and Nicobar Islands.
The evergreen forest is well stratified — it has distinct layers. Near the ground, shrubs and creepers cover the floor; above them stand short-structured trees, and rising over everything are tall trees that reach great heights of 60 metres or more. Because there is no definite season for shedding leaves, flowering, or fruiting, these forests appear green all year round. Important species include rosewood, mahogany, aini, and ebony.
The semi-evergreen forests appear in the less rainy parts of these same regions. They hold a mixture of evergreen and moist deciduous trees, and the climbers growing under the canopy give the forest its evergreen character. Main species here are white cedar, hollock, and kail.
A common confusion: evergreen forests do not mean the trees never shed leaves. They shed leaves, but different trees do so at different times, so the forest as a whole never looks bare.
The book also records a historical shift here. The British understood the economic value of Indian forests and began large-scale exploitation. They changed the very structure of forests — oak forests in Garhwal and Kumaon were replaced by pine (chir) because pine was needed to lay railway lines. Forests were cleared for tea, rubber, and coffee plantations, and timber was used in construction because it insulates against heat. In this way, the protective use of forests gave way to commercial use.
Tropical Deciduous Forests
These are the most widespread forests in India, also called monsoon forests. They grow where rainfall is between 70 and 200 cm. Based on water availability, they split into moist deciduous and dry deciduous.
Moist deciduous forests occur where rainfall is between 100 and 200 cm. They are found in the northeastern states along the foothills of the Himalayas, the eastern slopes of the Western Ghats, and Odisha. The main species are teak, sal, shisham, hurra, mahua, amla, semul, kusum, and sandalwood.
Dry deciduous forests cover vast areas where rainfall ranges between 70 and 100 cm. On their wetter margins they grade into moist deciduous forests, and on their drier margins into thorn forests. They are found in the rainier parts of the Peninsula and the plains of Uttar Pradesh and Bihar. In the higher-rainfall regions of the Peninsular plateau and the northern Indian plain, these forests take on a parkland landscape — open stretches where teak and other trees stand interspersed with patches of grass. When the dry season begins, the trees shed their leaves completely, and the forest looks like a vast grassland with naked trees all around. Common trees are tendu, palas, amaltas, bel, khair, and axlewood.
In the western and southern parts of Rajasthan, vegetation cover is very scanty because of low rainfall and overgrazing.
Tropical Thorn Forests
These occur where rainfall is less than 50 cm. They consist of a variety of grasses and shrubs, and they cover the semi-arid areas of southwest Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh, and Uttar Pradesh. Plants remain leafless for most of the year, giving the landscape the look of scrub vegetation. Important species are babool, ber, wild date palm, khair, neem, khejri, and palas. Tussocky grass grows up to a height of 2 metres as the undergrowth.
Montane Forests
In mountainous areas, temperature falls as altitude rises, and the natural vegetation changes correspondingly. Mountain forests are classified into two types: northern mountain forests and southern mountain forests.
Northern Mountain Forests
The Himalayan ranges show a succession of vegetation from tropical to tundra, changing with altitude:
- Deciduous forests occupy the foothills.
- Between 1,000 and 2,000 metres, wet temperate forests take over.
- In the higher hill ranges of northeastern India, the hilly areas of West Bengal, and Uttarakhand, evergreen broadleaf trees like oak and chestnut dominate.
- Between 1,500 and 1,750 metres, pine forests are well developed, with chir pine as a very useful commercial tree.
- Deodar, a highly valued endemic species, grows mainly in the western part of the Himalayan range. Its wood is durable and used in construction.
- Chinar and walnut, which sustain the famous Kashmir handicrafts, also belong to this zone.
- Blue pine and spruce appear at altitudes of 2,225 to 3,048 metres, and temperate grasslands are found in many places here.
- In the higher reaches, there is a transition to alpine forests and pastures. Silver firs, junipers, pines, birch, and rhododendrons occur between 3,000 and 4,000 metres.
- These alpine pastures are used extensively for transhumance by tribes like the Gujjars, the Bakarwals, the Bhotiyas, and the Gaddis.
The southern slopes of the Himalayas carry thicker vegetation because they receive more precipitation than the drier north-facing slopes. At the highest altitudes, mosses and lichens form part of the tundra vegetation.
Southern Mountain Forests
These are found in three distinct areas of Peninsular India: the Western Ghats, the Vindhyas, and the Nilgiris. Because these areas lie close to the tropics and rise only about 1,500 metres above sea level, the vegetation is temperate in the higher regions and subtropical on the lower regions of the Western Ghats, especially in Kerala, Tamil Nadu, and Karnataka.
The temperate forests here are called sholas in the Nilgiris, Anaimalai, and Palani hills. Other trees of economic significance include magnolia, laurel, cinchona, and wattle. Such forests are also found in the Satpura and Maikal ranges.
Littoral and Swamp Forests
India has a rich variety of wetland habitats. About 70 per cent of this comprises areas under paddy cultivation, and the total wetland area is 3.9 million hectares. Two sites — Chilika Lake in Odisha and Keoladeo National Park in Bharatpur — are protected as waterfowl habitats under the Ramsar Convention, an international agreement among member states of the United Nations.
The country's wetlands are grouped into eight categories:
| Category | Location |
|---|---|
| Reservoirs of the Deccan Plateau, lagoons and other wetlands of the southern west coast | South India |