• Climate, soil, and topography influence Natural Vegetation.
• Rainfall and temperature are the major climatic factors that affect vegetation.
• Annual rainfall determines the type of vegetation.
• Temperature is the main factor in hilly regions above 900 meters.
• Vegetation in the Himalayas changes with altitude from tropical to alpine.
• Soil plays a significant role in some regions like mangrove and swamp forests.
• Topography is responsible for minor vegetation types like alpine flora and tidal forests.

Annual Rainfall	Type of Vegetation
200 cm or more	Evergreen Rain Forests
100 to 200 cm	Monsoon Deciduous Forests
50 to 100 cm	Drier Deciduous or Tropical Savanna
25 to 50 cm	Dry Thorny Scrub (Semi-arid)
Below 25 cm	Desert (Arid)

Classification of Natural Vegetation of India

• Classification of Natural Vegetation of India is primarily based on spatial and annual variations in rainfall. Temperature, soil and topography are also considered.
• India’s vegetation can be divided into 5 main types and 16 sub-types as given below.

1. Moist Tropical Forests

• Tropical Wet Evergreen
• Tropical Semi-Evergreen
• Tropical Moist Deciduous
• Littoral and Swamp

2. Dry Tropical Forests

• Tropical Dry Evergreen
• Tropical Dry Deciduous
• Tropical Thorn

3. Montane Sub-tropical Forests

• Sub-tropical broad leaved hill
• Sub-tropical moist hill (pine)
• Sub-tropical dry evergreen

4. Montane Temperate Forests

• Montane Wet Temperate
• Himalayan Moist Temperate
• Himalayan Dry Temperate

5. Alpine Forests

• Sub-Alpine
• Moist Alpine scrub
• Dry Alpine scrub

Forest Type in India	% of Total Area
Tropical Moist Deciduous	37
Tropical Dry Deciduous	28
Tropical Wet Evergreen	8
Sub-Tropical Moist Hill	6
Tropical Semi-Evergreen	4
Rest below 4 %

A. Moist Tropical Forests

Tropical Wet Evergreen Forests or Rain Forests

• Tropical Wet Evergreen Forests or Rain Forests have climatic conditions characterized by:
  • Annual rainfall exceeding 250 cm
  • Annual temperature around 25°-27°C
  • Average annual humidity exceeding 77%
  • Distinctly short dry season
• Characteristics of these forests include:
  • Evergreen trees that do not shed leaves together due to high heat and humidity
  • Mesosphytic plants adapted to neither too dry nor too wet climates
  • Lofty trees that reach 45-60 meters in height
  • Thick canopy of foliage that appears like a green carpet from above
  • Less undergrowth due to the lack of sunlight reaching the ground
• Distribution of these forests:
  • Western side of the Western Ghats (500 to 1370 meters above sea level)
  • Some regions in the Purvanchal hills
  • Andaman and Nicobar Islands
• Timber of these forests:
  • Hardwood that is fine-grained, hard, and durable
  • High commercial value but challenging to exploit due to dense undergrowth, absence of pure stands, and lack of transport facilities
  • Important species include mahogany, mesua, white cedar, jamun, canes, and bamboo.
• 

Tropical Semi-Evergreen Forests

• Tropical Semi-Evergreen Forests are transitional forests between wet evergreen and deciduous forests
• They are drier compared to wet evergreen forests
• Annual rainfall is 200-250 cm and mean annual temperature varies from 24°C to 27°C
• Found in Western coast, Assam, lower slopes of Eastern Himalayas, Odisha, and Andamans
• The forests are less dense and more gregarious than wet evergreen forests
• Many species of trees, buttressed trunks with abundant epiphytes
• Important species include laurel, rosewood, mesua, thorny bamboo, white cedar, Indian chestnut, champa, mango, etc.
• Hardwood timber is similar to that in tropical evergreen forests, but the stands are more pure and less dense, making the timber industry better here.
• 

Tropical Moist Deciduous Forests

• Climatic Conditions:
  • Annual rainfall: 100 to 200 cm.
  • Mean annual temperature: about 27°C.
  • Average annual relative humidity: 60 to 75%.
  • Spring and summer are dry.
• Characteristics:
  • Trees drop their leaves during spring and early summer when moisture is scarce.
  • Irregular top storey (25 to 60 m).
  • Heavily buttressed trees and fairly complete undergrowth.
  • Large tracts cleared for cultivation.
  • Appearance is bare in extreme summers (April-May).
• Distribution:
  • Belt along the Western Ghats surrounding the evergreen forests.
  • Strip along the Shiwalik range including terai and bhabar from 77° E to 88° E.
  • Manipur and Mizoram.
  • Hills of eastern Madhya Pradesh and Chhattisgarh.
  • Chota Nagpur Plateau.
  • Most of Odisha.
  • Parts of West Bengal and Andaman and Nicobar islands.
• Timber:
  • Valuable timber like Teak.
  • Main species found in these forests are teak, sal, laurel, rosewood, amla, jamun, bamboo, etc.
  • Easy to exploit due to their high degree of gregariousness (more pure stands).
• 

Littoral and Swamp Forests

• Littoral and Swamp Forests can grow in fresh as well as brackish water.
• They occur in and around the deltas, estuaries and creeks prone to tidal influences.
• Littoral forests occur at several places along the coast while swamp forests are confined to the deltas of the Ganga, the Mahanadi, the Godavari, the Krishna and the Cauvery.
• Dense mangroves occur all along the coastline in sheltered estuaries, tidal creeks, backwaters, salt marshes and mudflats.
• The most pronounced and the densest is the Sunderban in the Ganga delta where the predominant species is Sundri (Heriteera).
• It provides useful fuel wood, hard and durable timber which is used for construction, building purposes and making boats.
• The important species found in these forests are Sundri, agar, rhizophora, screw pines, canes and palms, etc.
• 

B. Dry Tropical Forests

Tropical Dry Evergreen Forests

• Tropical Dry Evergreen Forests are found along the coasts of Tamil Nadu.
• They experience annual rainfall of around 100 cm, mostly from the north-east monsoon winds in October to December.
• The mean annual temperature is about 28°C, and the mean humidity is about 75%.
• Despite the low rainfall, these forests have evergreen characteristics with short-statured trees, up to 12 m high, and a complete canopy.
• Bamboos and grasses are not conspicuous in these forests.
• The important species found in these forests are jamun, tamarind, neem, etc.
• However, most of the land under these forests has been cleared for agriculture or casuarina plantations.
• 

Tropical Dry Deciduous Forests

• The climatic conditions of these forests include an annual rainfall of 100-150 cm.
• The characteristics of these forests are similar to moist deciduous forests, where they shed their leaves during the dry season.
• The major difference is that these forests can grow in areas with comparatively less rainfall.
• They represent a transitional type between moist deciduous forests on the wetter side and thorn forests on the drier side.
• The canopy is closed but uneven, and the forests are composed of a mixture of a few species of deciduous trees that rise up to a height of 20 meters.
• There is enough light that reaches the ground, allowing for the growth of grass and climbers in the undergrowth.
• These forests occur in an irregular wide strip running from the foot of the Himalayas to Kanniyakumari, except in Rajasthan, Western Ghats, and West Bengal.
• The important species found in these forests are teak, axlewood, rosewood, common bamboo, red sanders, laurel, satinwood, etc.
• Large tracts of these forests have been cleared for agricultural purposes, and they suffer from overgrazing, fires, and other human impacts.
• 

Tropical Thorn Forests

• The climatic conditions of these forests include an annual rainfall of less than 75 cm.
• Humidity is less than 50 percent and the mean temperature ranges from 25°-30°C.
• The trees in these forests are low, with a maximum height of 6 to 10 meters, and they are widely scattered.
• Acacias and Euphorbias are very prominent in these forests.
• The Indian wild date is a common species, and some grasses also grow during the rainy season.
• These forests are found in Rajasthan, southwestern Punjab, western Haryana, Kachchh, and neighboring parts of Saurashtra.
• In the Thar desert, these forests degenerate into a desert type.
• Similar forests also grow on the leeward side of the Western Ghats, covering large areas of Maharashtra, Karnataka, Telangana, Andhra Pradesh, and Tamil Nadu.
• The important species found in these forests are neem, babul, cacti, etc.
• 

C. Montane Sub-Tropical Forests

Sub-tropical Broad-leaved Hill Forests

• The climatic conditions of these forests include a mean annual rainfall ranging from 75 cm to 125 cm.
• The average annual temperature is 18°-21°C, and humidity is around 80 percent.
• These forests are found in the Eastern Himalayas, to the east of 88°E longitude, at altitudes varying from 1000 to 2000 meters.
• The forests are characterized by evergreen species, with commonly found species such as evergreen oaks, chestnuts, ash, beech, sals, and pines.
• Climbers and epiphytes (plants that grow non-parasitically on other plants) are common in these forests.
• These forests are not as distinct in the southern parts of the country and occur only in the Nilgiri and Palni hills at 1070-1525 meters above sea level.
• They are often referred to as “stunted rainforests” and are not as luxuriant as the true tropical evergreen forests.
• Sub-types of these forests can be found in the higher parts of the Western Ghats, such as Mahabaleshwar, the summits of the Satpura and the Maikal Range, highlands of Bastar, and Mt. Abu in the Aravali Range.
• 

Sub-tropical Moist Pine Forests

• The distribution of these forests is in the Western Himalayas, between 73°E and 88°E longitudes, at elevations ranging from 1000 to 2000 meters above sea level.
• They can also be found in some hilly regions of Arunachal Pradesh, Manipur, Naga Hills, and Khasi Hills.
• The dominant tree species in these forests is Chir or Chil, which forms pure stands.
• Chir is valuable for its timber, which is used for furniture, boxes, and buildings.
• Chir is also used for producing resin and turpentine.
• 

Sub-tropical Dry Evergreen Forests

• These forests are found in the Bhabar, the Shiwaliks, and the western Himalayas up to about 1000 meters above sea level.
• The annual rainfall in these areas ranges from 50-100 cm, with lower rainfall (15 to 25 cm) occurring during December-March.
• The summers are hot, and the winters are very cold in these regions.
• The forests are characterized by low scrub vegetation with small evergreen stunted trees and shrubs.
• Olive, Acacia modesta, and Pistacia are the most predominant species in these forests.
• 

D. Montane Temperate Forests

Montane Wet Temperate Forests

• These forests are found at an elevation of 1800 to 3000 meters above sea level.
• The mean annual rainfall in these areas ranges from 150 cm to 300 cm.
• The mean annual temperature is about 11°C to 14°C, and the average relative humidity is over 80 percent.
• These forests are found in the higher hills of Tamil Nadu and Kerala, as well as in the Eastern Himalayan region.
• The forests are characterized by closed evergreen vegetation, with trunks having large girth.
• Branches are covered with mosses, ferns, and other epiphytes.
• The trees in these forests rarely exceed a height of 6 meters.
• Important species in these forests include Deodar, Chilauni, Indian chestnut, birch, plum, machilus, cinnamomum, litsea, magnolia, blue pine, oak, hemlock, and others.
• 

Himalayan Moist Temperate Forests

• These forests occur in the temperate zone of the Himalayas, at elevations between 1500 and 3300 meters.
• They cover the entire length of the Himalayan mountain range in regions such as Kashmir, Himachal Pradesh, Uttarakhand, Darjeeling, and Sikkim.
• The annual rainfall in these areas varies from 150 cm to 250 cm.
• These forests are mainly composed of coniferous species, with trees forming mostly pure stands.
• The trees in these forests are 30 to 50 meters tall, and important species include pines, cedars, silver firs, spruce, and others.
• The forests have a high but fairly open canopy, with shrubby undergrowth including oaks, rhododendrons, and some bamboos.
• The timber from these forests is of fine quality and is used for construction, timber, and railway sleepers.
• 

Himalayan Dry Temperate Forests

• These forests are found in the inner dry ranges of the Himalayas, where the southwest monsoon is very feeble.
• Areas such as Ladakh, Lahul, Chamba, Kinnaur, Garhwal, and Sikkim are known to have these forests.
• The precipitation in these areas is below 100 cm and mostly in the form of snow.
• These forests are characterized by coniferous trees and xerophytic shrubs, with main tree species including deodar, oak, ash, olive, and others.
• 

E. Alpine Forests

• These forests are found at altitudes ranging between 2,900 to 3,500 meters.
• They can be divided into three types: sub-alpine, moist alpine scrub, and dry alpine scrub.
• Sub-alpine forests occur in lower alpine scrub and grasslands. They are a mixture of coniferous and broad-leaved trees, with coniferous trees reaching about 30 meters in height and broad-leaved trees reaching only 10 meters. Important species include fir, spruce, rhododendron, and others.
• Moist alpine scrub is a low evergreen dense growth of rhododendron, birch, and other species. It occurs from 3,000 meters and extends up to the snowline.
• Dry alpine scrub is the uppermost limit of scrub xerophytic dwarf shrubs, found at elevations over 3,500 meters above sea level in the dry zone. Important species include juniper, honeysuckle, Artemesia, and others.
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