India has numerous vegetation types resulting largely from the considerable heterogeneity in climate, soils, topography, and human land-use.

For instance, in peninsular India, there exist the Western and Eastern Ghats mountain ranges abutting the coastline and encircling the Deccan Plateau. As a result, elevation ranges from sea level to over 2500 m above sea level (a.s.l.). The Western Ghats significantly alter the climatic regime within India by serving as an orographic barrier to the rain-bearing southwest monsoon winds, resulting in a sharp precipitation gradient in the western side of the peninsula and bringing drier conditions to the rest of the peninsula. Similarly, the northern and eastern parts of India are bordered by the highest mountain chain in the world, the Himalaya, which exerts a tremendous influence on the climate, hydrology, and geomorphology of the subcontinent. Soils vary considerably as a consequence, particularly in response to topography, climate, and parent material. Finally, the remarkable biogeographic history of the Indian subcontinent has resulted in plants of numerous biogeographic affinities being present in most assemblages. Superimposed on this are the impacts of a diverse fauna including, notably, humans, who have occupied the region continuously for tens of thousands of years.

A number of now-classic vegetation type classifications (e.g., Champion and Seth 1968; Puri et al. 1983; Pascal 1986) have been attempted in the past for regions within India. Here, we follow the most recent, comprehensive classifications (Roy et al. 2015; Reddy et al. 2015) that are based on satellite data that have been ground-truthed and vetted by experts.

Tropical evergreen forests, characterized by tall (> 30 m), often buttressed, evergreen trees, and multiple strata, are largely confined to the windward, high-rainfall zones of the Western Ghats, north-eastern India, and the Andaman and Nicobar Islands. As the rainfall decreases, so does the ratio of evergreen-to-deciduous plants.

Tropical semi-evergreen forests, characterized by a predominance (> 75%) of evergreen trees, as well as climbers and epiphytes, are found in proximity to tropical evergreen and tropical moist deciduous forests.

Tropical moist deciduous forests are characterized by the dominance of deciduous species, an irregular top storey and a lower storey dominated by evergreen trees and shrubs. These forests are widespread where the annual rainfall typically exceeds 1000 mm but is less than 2000 mm, in regions including the Western Ghats, central and north-eastern India, and the Andaman and Nicobar Islands. They frequently grade into tropical semi-evergreen and tropical dry deciduous forests.

Tropical dry deciduous forests are characterized by intermediate (< 20 m), open canopies, consisting almost entirely of deciduous species that become leafless for 1-4 months, grasses, and frequent fires. These forests are found in large parts of peninsular India and the Himalayan foothills in the drier zones. They are often dominated by teak (Tectona grandis) where they occur in southern, western, and central India and by sal (Shorea robusta) in northern, eastern, and central India. Teak-bearing forests transition into sal-bearing forests in central, northern, and eastern India in the 700 mm – 1500 mm annual rainfall zone (Gadgil and Meher-Homji 1986). Tropical dry deciduous forests — and even drier vegetation types consisting of tree-grass mixtures — that have historically been classified as forests are now often classified as savannas (Ratnam et al. 2016).

Tropical thorn forests are characterized by short (< 10 m), open canopies, consisting largely of thorny, leguminous (e.g., Acacia), hardwood species, and sun-loving shrubs and grasses. These forests are found in the semi-arid parts of peninsular, northern and north-western India. A number of moist and dry open-canopied (< 10%) scrub vegetation types consisting largely of evergreen or deciduous shrubs are distributed throughout in the drier parts of India.

Grasslands, characterized by the dominance of grasses and forbs, and the near absence of trees, are found both on hilltops and in plains throughout the country. Tree presence in grasslands may be limited by one or more factors, including climate (e.g., low rainfall, low temperatures), soil conditions (e.g., salinity, low soil depth, waterlogging), and the prevalence of fire and mammalian herbivory. Major grassland types include coastal grasslands (found along coasts), riverine alluvial grasslands (found along banks of large rivers), montane grasslands (found in mountainous regions and including alpine meadows and steppe), sub-Himalayan tall grasslands of Terai (found at the convergence of Himalayan foothills and Gangetic plains), tropical savannas (found in central, western, and southern India; note that savannas, which are tree-grass mixtures, are often treated as a distinct vegetation type), and wet grasslands (found in waterlogged areas, usually close to water bodies) (Chandran 2015).

Tropical dry evergreen forests, characterized by the dominance (> 75%) of hard-leaved evergreen woody plants, are largely restricted to the Eastern Ghats of Andhra Pradesh and Tamil Nadu.

Subtropical broad-leaved hill forests, characterized by a mixture of wet evergreen and temperate forest species, and dominated by species in the Lauraceae, are found in the Western Ghats, north-eastern India, the Aravalli, and the lower slopes of the Himalaya.

Subtropical dry evergreen forests, characterized by small-leaved evergreen species, are found in the foothills of the Himalayas up to 1500 m a.s.l. and a prolonged dry season.

Subtropical pine forests are fire-prone forests dominated by evergreen conifers and grasses. They are found along the drier (often, but not always, south-facing) slopes at the lower elevations of the Himalayas and on hilly tracts of north-eastern India.

Montane wet temperate forests are closed-canopied evergreen forests characterized by relatively short (< 15 m) canopies, mosses, ferns, epiphytes and woody climbers. These forests are found in the higher (> 1500 m a.s.l.) elevations of the eastern Himalaya, north-eastern India, and the Western Ghats. In the Western Ghats, these forests are known as shola and are restricted to the Nilgiris, Palnis, Anamalais and Tirunelveli hills. These stunted forests are found in frost-free valleys amidst montane grasslands.

Himalayan moist temperate forests are conifer-dominated and tall-canopied (up to 40 m) forests found throughout the Himalaya and hilly tracts of north-eastern India, from about 1500 m to 3000 m a.s.l.

Himalayan dry temperate forests are sometimes distinguished as a distinct forest type (but see Singh and Singh 1987). Like their moist counterparts, dry temperate forests are also conifer-dominated, but have a high frequency of xerophytic shrubs and are found in relatively higher and drier (< 2000 mm annual rainfall) tracts of the Himalaya.

Subalpine forests are conifer-dominated, short-canopied (< 15 m) forests that bear numerous epiphytes. They occur beyond Himalayan temperate forests and up to the treeline, grading into alpine vegetation types such as alpine meadows.

Littoral and swamp forests are evergreen-species dominated forests found where the soil is submerged in saline or fresh water, periodically or throughout the year. Pneumatophores, and stilt, knee, and buttress roots are common adaptations to the submerged conditions. Littoral and tidal swamp forests (which include mangrove scrub and mangrove forests) consist of halophytic plants with seeds that germinate while still on the parent tree and are found in river deltas along the coastal regions of India, including the Andaman and Nicobar Islands. Freshwater swamp forests are found in waterlogged locations in the wet forests of southern Western Ghats, Eastern and Western Himalaya, and the Ganges and Brahmaputra valleys.

A number of subtypes of these major vegetation types exist across the Indian subcontinent. The cited literature may be consulted for further details.

References

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CHANDRAN M. (2015) Grassland vegetation of India: An update. In: Rawat G, Adhikari B (eds) Ecology and management of grassland habitats in India. Wildlife Institute of India, Dehradun, India

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