India has a vast range of forests, alpine and sub-alpine areas, and temperate and subtropical regions, while tropical ecosystems cover 17% of its area. These can be further divided into totally 162 different kinds of vegetation based on climate, soil, topography and biotic factors, including human activity, according to Champion and Seth. This number includes both primary and secondary forests.
Rainforests are found in regions with Mean Annual Rainfall (MAR) of more than 2500 millimeters, where most months of the year receive measurable rainfall, and mean annual temperatures are around 26 Degrees Celsius. These are regions of high biodiversity, and have trees reaching up to 60 meters tall. Rosewood, ebony and mahogany are some trees found here. In the Himalayas, animals such as the Leaf muntjac, hoolock gibbon, sun bear, gaur, red panda, and more than 500 species of birds are found. In the south elephants, sloth bear, niligris langur occur. According to World Wide Fund for Nature (WWF), these regions also have a concentration of endemic aquatic animals, including 100 fish and 100 amphibian species and 20% of its mollusks. These forests are found in Andaman and Nicobar Islands, Western Ghats in Karnataka, Tamil Nadu and Kerala, and North-Eastern India. This type includes Andaman Islands Rain Forests, Nicobar Islands Rain Forests Mizoram-Manipur-Kachin Rain Forests, and South Western Ghats Montane Rain Forests.
Moist Semi-Evergreen Forests
These types of forests are found in areas with Mean Annual Rainfall totals of 2,000 to 2,500 millimeters. There is a mixture of evergreen and deciduous tree species such as Bambusa, Terminalia, Dipterocarpus, Albizzia, Shorea, and Cinnamomum. Tigers, elephants, gaur, clouded leopard, wild water buffalo, Indian rhinocerous, and more than 300 bird species are found here. These forests are found along the western coast, eastern Orissa and Assam. The forests in this category are Brahmaputra Valley Semi-Evegreen Forests.
Moist Deciduous Forests
These forests are found in areas with Mean Annual Rainfall of 1,000 to 2,000 millimeters, with a short dry period in summer when trees shed their leaves. The forests are 25 meters tall, and species are predominately deciduous trees with evergreen species mostly in the lower storeys. Important tree species are Tectona grandis or teak, Terminalia, Dalbergia or Rosewood, Shorea or sal, and Adina cordifolia. The lion-tailed macaque, Niligiri tahr, tiger and elephants are found here according to WWF. These forests are found in lower Himalayan ranges in Punjab and Assam, Gangetic Plains, Andhra Pradesh and Maharashtra. South Western Ghats Moist Deciduous Forests, Eastern Highlands Moist Deciduous Forests, Lower Gangetic Plains Moist Deciduous Forests, Upper Gangetic Plains Moist Deciduous Forests, Malabar Coast Moist Forests, Maldives-Lakshadweep-Chagos Archipelago Tropical Moist Forests, and South Western Ghats Moist Deciduous Forests are examples.
These wetlands are found along river deltas which are flooded with sea water everyday. These are home to salt-tolerant species of evergreen plants, with special breathing roots. Trees reach 3 to 15 meters tall. Rhizophora and Avicennia species are found here. Thick dense mangrove forests are found at river deltas of Godavari-Krishna and Sundarbans, and Indus River Delta-Arabian Sea Mangroves. Sundarbans are famous also for their tigers and many species of birds.
Marshes occur further inland in the deltas, and comprise the intertidal areas between mangroves and land. It is flooded only by high tides, and so salt water levels are lower than in mangroves. They are marshy due to accumulation of mud and organic matter. Tall trees can reach up to 20 meters. Avicennia, Excoecaria, Bruguiera and Nipa are common tree species. Flamingos, Sarus crane, White Stork and the Asian open bill stork are some birds found here according to WWF. Rann of Kutch Seasonal Salt Marsh is one such marsh.
Dry Evergreen Forests
The dry period is longer than the wet period here, even though Mean Annual Rainfall can be around 1,000 millimeters. The forests are dense with short and evergreen tree species growing up to 10 to 15 meters tall. Tree species such as Calotropis, Cassia, Canthium, and Zizyphus are common. Blackbuck, monitor lizards, and star-tortoises are found here. East Deccan Dry Evergreen Forests is found along the south eastern coast in Tamil Nadu and Andhra Pradesh.
Dry Deciduous Forests
Dry Deciduous forests are found in areas with Mean Annual Rainfall totals of 700 to 1,000 millimeters, and their native trees are usually 8 to 20 meters tall. In the dry long summer all trees shed their leaves, and are deciduous. Trees found are not dense and there is more grass and shrubs. In north India sal is important and in south India teak. These forests have nearly a hundred species of animals, including tigers, Asian elephants, sloth bears, leopard, black buck and chinkaras, and many hundreds of bird species. Central Deccan Plateau Dry Deciduous Forests, South Deccan Plateau Dry Deciduous Forests, Chhota-Nagpur Dry Deciduous Forests, Khathiar-Gir Dry Deciduous Forests, and Narmada Valley Dry Deciduous Forests are found in peninsular regions with more rainfall, and in Uttar Pradesh and Bihar.
The Terai-Duar Savanna and Grasslands are found in an area that is warm and receives minimal rainfall. They have some of the tallest grasses in the world according to WWF. Tigers, swamp deers, the greater one-horned Rhino and many rare birds such as the spiny babbler, grey-crowned prinia, and Manipur bush-quail occur in grasslands.
These forests occur in areas receiving Mean Annual Rainfall amounts of 200 to 700 millimeters, and where the dry season is hot and very long. The soil is sandy and these are deserts, where there are no trees. In more moist areas, the trees are up to ten meters tall, thorny, deciduous and xerophytic, adapted to survive drought conditions. Calotropis, Euphorbia, Prosopis and Adhatoda. Camels are common animals here. Thorn forests are mainly found in Rajasthan, Gujarat and south Punjab. Deccan Thorn Scrub Forests, Northwestern Thorn Scrub Forests, and Thar Desert are examples.
Temperate Broadleaf and Mixed Forests
All temperate forests in India are found at high altitudes, although the conditions between the eastern and western parts of the mountains vary, giving rise to their own distinct vegetation types.
Himalayan Dry Temperate Forests
As their name suggests, they are found in the Himalayas between 3,000 and 4,000 meters above sea level in the western section of the mountains where the rainfall is less, varying between Mean Annual Rainfall totals of 80 and 800 millimeters. Annual temperatures are between 5.8 and 16.8 degrees Celsius, but can fall below 0 degrees Celsius. The common species here are conifers such as Cedrus, Pinus, Juniperus, and Abies, and broad-leaved species such as Acer, Fraxinus, and Quercus. Snow leopard, blue sheep, Himalayan tahrs, snow geese, the Tibetan sand grouse, and more than 300 species of birds are found here, according to the WWF.
East Himalayan Moist Temperate Forests
These forests are found between 2,300 and 3,000 meters above sea level. The conifers are silver fir to hemlock, and have more of broadleaved species such as Acer, Magnolia, Betula, and Rhododendrons. Golden langur, clouded leopard, lesser Panda, and goat antelope and 500 bird species live here according to WWF. Examples of this forest are the Eastern Himalayan Broadleaf Forests.
Sub-alpine forests occur between altitudes of 2,900 and 3,500 meters, with Mean Annual Rainfall of 649 millimeters, and mean temperatures of 12.8 degrees Celsius, though temperatures can fall below 0 degrees Celsius. The Sub-alpine forests have deciduous and evergreen tree species such as oak, fir, and blue-pine. Other plants including short trees, shrubs and herbs such as rhododendrons, chrysanthemum, and primula. Examples of this forest are Eastern Himalayan Subalpine Conifer Forests, and Western Himalayan Subalpine Conifer Forests.
Alpine and Montane Grasslands and Steppe
Alpine conditions are found only in the northern parts of the country in the Himalayas above the timber line at altitudes above 3,500 to 4,500 meters. It is cold with snowfall over many months with little vegetation. The snow leopard, wolf, Himalayan black bear and Red Panda, are common animals in this regions. There are two types of vegetation here.
Moist Alpine Scrub
These alpine types have low dense scrub species such as Rhododendrons and Lonicera, examples of moist alpine scrub habitats being seen in the Eastern Himalayan Alpine Shrub and Meadows, Northwestern Himalayan Alpine Shrub and Meadows, and Western Himalayan Alpine Shrub and Meadows.
Dry Alpine Scrub
Dry scrub areas have xerophytic low shrubs, and are also called alpine steppes. They are fond next to temperate forests. Mean Annual Rainfall is under 350 millimeters. Junipers and Lonicera are common plant species found here. Examples are Central Tibetan Plateau Alpine Steppe, Karakoram-West Tibetan Plateau Alpine Steppe . Above 4,500 meters, there is only snow, where no plants can survive.
Threats and Conservation Efforts
Indian forests house 45,000 species of flora and 81,000 fauna species, many of which are endemic, found only in India or an even narrower specific range within it. The country has 597 Protected areas amounting to 4.75% of its geographical area set aside for conservation of these species. Clearing of forests for timber, and for activities such as agriculture, mining, and the construction of hydroelectric power plants are major large scale reasons threatening them. On a small scale extraction of firewood, non-timber resources, over-grazing, and poaching degrade and threaten species and forests.