Ecologists call large, distinct, easily differentiated formations or communities having distinct flora and fauna are biomes. Biomes are generally recognized by and named after the dominant plant species or community.
Vegetation of India
The most important factors used in this classification of Indian vegetations are rainfall, temperature, edaphic factors, biotic influence and life forms. These are two common types of plant formation in India.
Champion and Seth (1968) have recognized the 16 major types of forests in India.
I. Moist Tropical forests
(1) Tropical Wet Evergreen Forests:
Western Ghats, Assam, Bengal, Mysore and Andamans e.g. Diterocapus, Hopea, Mangifera, Emblica, Michelia, Lagerostroemia.
(2) Tropical moist semi-evergreen forests:
Western Ghats, Assam, Orissa e.g. Terminalia, Shorea, Michelia, Eugenia.
(3) Tropical moist deciduous forests:
Western Ghats, Chota Nagpur, Khasi Hills, e.g. Albizzia, Melia, Terninalia, Eugenia.
(4) Littoral and Swamp forests:
These forests comprise mostly evergreen and occur along sea coast in wet and marshy areas. E.g. Rhizophora, Phoenix, Ipomea, Phragmites etc.
II. Dry Tropical Forests
5. Tropical dry deciduous forest:
These forests are distributed almost throughout the country except Kashmir, beyond Bengal, Rajasthan and Western Ghats. E.g. Tectona grandis, Terminalia, Emblica, Acacia, Zizypus.
6. Tropical Dry deciduous forests of South East Deccan Region:
Some parts of Tamil Nadu and Karnataka coasts. Eg. Ixora, Sterculia.
7. Tropical Thorn Forest:
W. Rajasthan, S. Punjab, Bundelkhand, Gujarat, Maharashtra, Madhya Pradesh and Tamil Nadu. E.g. Capparis, Euphorbia, Zizypus.
III. Montane (Mountainous) Subtropical Forest
8. Subtropical board leaved hill forests:
These forests are dense have predominantly evergreen species and occur in relatively moist areas in eastern Himalayas, Bengal, Assam, Khasi Hills, Nilgiri, Mahabaleshwar, e.g. Quercus, Ficus, Bamboos, Populus, Mangifera.
9. Subtropical pine forests:
Western Himalaya and Khasi Jayantia hills of Assam. E.g. Pinus roxbourghii and P. khasya.
10. Subtropical dry evergreen forests:
Lower elevations of Himalayas have xerophytic forests containing ‘mainly thorny and small leaved evergreen species. Eg. Acacia, Olea.
IV. Montane Temperate Forests
11. Montane wet temperate forests:
Eastern Himalaya with high rainfall as Sholas. Eg. Betula, Acer, Populus, Ulmus.
12. Himalayan moist temperate forests:
Central and Western Himalaya. Eg. Contoneaster, Berbesis, Quercus, Cedrus, Picea, Abies.
13. Himalayan dry temperate forests:
Western Himalaya UP, HP, Punjab to Kashmir. Eg. Picea, Larix, Juniperus.
V. Alpine Forests
14. Sub Alpine Forests:
In Himalayas above 3000 m. e.g. Cotoneastor, Lonicera, Smilax.
15. Moist Alpine Scrub:
Throughout Himalaya above timber line to 5500 m. e.g. Juniperus, Rhododendron.
16. Dry-alpine scrub:
In low rainfall areas as xerophytic e.g. Juniperus, Eurotia, Salix etc. upto 5500 m.
b. Grassland Vegetation:
Natural grasslands are not present during succession. Three types of grasslands occur in India.
(1) Xerophilous: dry regions of north west India under semi deserts conditions.
(2) Mesophilous: flats grass or savannas in deciduous forest of U.P
(3) Hygrophilous: wet savannas
These above basic types of grassland are further divided into eight subtypes which is named on dominant species.
Keystone species: Within biological communities, some species may be important in determining the ability of large no. of other species to persist in the community. These crucial species are known as keystone species.