Phytogeography is the study of the distribution of plant species across geographical regions, considering factors such as climate, soil, altitude, and biotic influences. India, with its vast territory and diverse climate, exhibits remarkable floristic diversity, leading to its division into distinct phytogeographical regions. Several botanists, notably J.D. Hooker and D. Chatterjee, have classified India into multiple phytogeographical zones based on vegetation types, climate, and floristic composition.
Major Phytogeographical Regions of India
communities and ecological characteristics:
- Western Himalayas
- Eastern Himalayas
- Indus Plain
- Gangetic Plain
- Central India
- Deccan Plateau
- Western Coast (Malabar)
- Assam
- Andaman and Nicobar Islands
1. Western Himalayas
- Location: Includes Jammu & Kashmir, Himachal Pradesh, and parts of Uttarakhand and Punjab.
- Climate: Varies from wet in the outer southern ranges to drier in the inner northern parts; annual rainfall between 100–200 cm; snowfall in winter.
- Vegetation: Divided into three altitudinal zones:
- Submontane (up to 1500 m): Dominated by Sal (Shorea robusta), Terminalia, and Acacia.
- Montane (1500–3500 m): Conifers like Pinus, Cedrus deodara, Picea, and Abies; broad-leaved trees such as Quercus (oaks) and Aesculus.
- Alpine (above 3500 m): Alpine meadows with herbaceous plants like Primula, Ranunculus, and Polygonum.
2. Eastern Himalayas
- Location: Sikkim, North Bengal, Arunachal Pradesh, Bhutan, and adjoining areas.
- Climate: Receives higher rainfall than the western Himalayas, with lush, dense forests.
- Vegetation: Rich in both tropical and temperate species, including Magnolia, Michelia, Rhododendron, and a high diversity of orchids and ferns. Alpine zones have species like Juniperus and Rhododendron.
3. Indus Plain
- Location: Covers parts of Punjab, Haryana, and Rajasthan.
- Climate: Arid to semi-arid, with low rainfall.
- Vegetation: Dominated by xerophytic (drought-resistant) shrubs and grasses such as Acacia, Prosopis, Salvadora, and Capparis. Riverine areas support Dalbergia sissoo and Populus.
4. Gangetic Plain
- Location: Extends from eastern Rajasthan through Uttar Pradesh, Bihar, and West Bengal.
- Climate: Humid subtropical, with fertile alluvial soils.
- Vegetation: Originally covered by moist and dry deciduous forests (Shorea robusta, Bombax ceiba, Terminalia), now largely replaced by agricultural crops; tall grasses like Saccharum and Themeda are common in the Terai.
5. Central India
- Location: Includes Madhya Pradesh, Chhattisgarh, and adjacent regions.
- Climate: Tropical, with a mix of dry and moist deciduous forests.
- Vegetation: Teak (Tectona grandis), Sal (Shorea robusta), and bamboo are dominant, along with a variety of shrubs and herbs.
6. Deccan Plateau
- Location: Occupies much of peninsular India south of the Gangetic plain and east of the Western Ghats.
- Climate: Tropical, with marked dry and wet seasons.
- Vegetation: Dry deciduous forests with species like Anogeissus, Acacia, Hardwickia, and Santalum album (sandalwood); in wetter areas, moist deciduous forests with Terminalia and Pterocarpus.
7. Western Coast (Malabar)
- Location: Narrow strip along the western coastline, including the Western Ghats.
- Climate: High rainfall due to the southwest monsoon.
- Vegetation: Tropical evergreen forests, rich in endemic species; includes Dipterocarpus, Hopea, and a wide variety of palms, bamboos, and orchids. The Western Ghats are recognized as a biodiversity hotspot.
8. Assam
- Location: Brahmaputra valley and adjoining hill regions (Naga, Khasi, Jaintia hills).
- Climate: High rainfall, humid.
- Vegetation: Dense tropical evergreen and semi-evergreen forests, with species like Dipterocarpus, Shorea, and a rich diversity of bamboos and orchids.
9. Andaman and Nicobar Islands
- Location: Bay of Bengal.
- Climate: Tropical, humid, with heavy rainfall.
- Vegetation: Tropical rainforests, mangroves, and coastal vegetation; high levels of endemism and unique species adapted to insular conditions.
Factors Influencing Phytogeographical Divisions
- Climatic Factors: Temperature, precipitation, humidity, and light intensity strongly influence plant distribution.
- Edaphic Factors: Soil type, fertility, and drainage.
- Biotic Factors: Human activity, grazing, and competition among species.
- Altitude and Topography: Especially significant in the Himalayan regions.
Significance of Phytogeographical Divisions
- Conservation: Understanding these divisions helps prioritize areas for conservation, especially biodiversity hotspots like the Western Ghats and Eastern Himalayas.
- Agriculture and Forestry: Guides selection of crops and tree species suitable for different regions.
- Research and Education: Provides a framework for botanical research and ecological studies.
Summary Table: Phytogeographical Regions of India
| Region | Key Features & Vegetation Types |
| Western Himalayas | Submontane, montane, alpine; conifers, oaks, alpine herbs |
| Eastern Himalayas | Tropical to alpine forests; rhododendrons, orchids, magnolias |
| Indus Plain | Arid; xerophytes, acacias, riverine forests |
| Gangetic Plain | Alluvial; moist/dry deciduous forests, tall grasses, agriculture |
| Central India | Dry/moist deciduous forests; teak, sal, bamboo |
| Deccan Plateau | Dry deciduous, scrub; sandalwood, acacia, terminalia |
| Western Coast (Malabar) | Tropical evergreen; dipterocarps, palms, high endemism |
| Assam | Evergreen/semi-evergreen; bamboos, orchids, dipterocarps |
| Andaman & Nicobar | Rainforest, mangroves; high endemism, coastal flora |