PHYTOGEOGRAPHY OF INDIA
Phytogeography:-
> Phytogeography is the study of distribution of plant species and elucidation of origin of flora.
> Distribution of plants is mainly controlled by climatic factors.
i. Temperature, Altitude, Precipitation, Atm moisture, Light intensity and duration.
ii. Type of soil.
iii. Biotic factors play an important role in distribution and establishment of species.
Phytogeographical regions of India:-
> Phyto geographical regions are also called as Botanical regions.
> D. Chatterjee has divided India in to 9 botanical zones.
1. Western Himalayas
2. Eastern Himalayas
3. Indus plains
4. Gangetic plains
5. Central India
6. Deccan
7. Western Coast of Malabar
8. Assam
9. Bay Islands of Andaman and Nicobar
1. Western Himalayas:-
- Northern India:- highest range of Himalayas.
- Climate and vegetation:- truly tropical at low altitude and temperate arctic type at high altitude.
- Northern mountain:- western, central and eastern zones.
- Western Himalayas:- North and South Kashmir, a part of Punjab.
- Rainfall:- 100 to 200 cm annually.
- Snowfall during winter.
- Divided into 3 subzones:
i) Submontane zone:- up to 1500 m altitude –Shivalik area – Shorea robusta.
ii) Temperate zone:- from 1500 m t0 3500 m altitude – oaks are dominant.
iii) Alpine zone:- above 3500 m up to snowline – dominated by conifers.
2. Eastern Himalayas:-
- Extend from Sikkim to upper Assam, Darjeeling.
- Divided into:
i) Tropical submontane zone:- warm humid climate – extend up to altitude of 1800 m – Sal forest.
ii) Temperate or montane zone:- upper temperate zone (3000-4000 m – conifers and Rhododendron, lower temperate zone (1800-3000 m – Oaks, Michelia).
iii) Alpine zone:- 4000 m up to snowline – absence of trees – dominated by shrubs and meadows – Rhododendron and Juniper.
- Considered to be richest vegetational units in the world consisting of foreign plant species.
3. Indus Plains:-
- Includes part of Punjab, Rajasthan, Kutch, Delhi and Gujarat.
- Characterized by dry hot summer and dry cold winter.
- Rainfall – 70 cm, in some regions – 10-15 cm.
- Soil is saline.
- Some parts have become desert due to excessive dryness.
- Vegetation – bushy and thorny.
- Acacia arabica, Salvadora are common.
4. Gangetic Plains:-
- One of the richest vegetational zones in India.
- Part of Delhi, whole of UP, Bihar, West Bengal and part of Orissa.
- Rainfall – 50 to 150 cm.
- Most land under cultivation.
- Crop plants – wheat, barley, maize, jowar, bajra, urad, moong, sugarcane, pea, potato, rice.
5. Central India:-
- Covers MP, Chhatisgarh, part of Orissa, Gujarat.
- Hilly area.
- Rainfall – 100-170 cm.
- Some places are at high altitude – 500 -700 m.
- Teak trees are common.
- Divided into:
i) Sal forest
ii) mixed deciduous forest
iii) thorny forest
6 Deccan:-
- Whole of Southern peninsular India including Satpura and Southern part of Godawari river.
- Rainfall – 100 cm.
- Divided into:
i) Deccan plateau – teak forest, Acacia, Santalum album.
ii) Coromandel coast – halophytic species.
7. Western Coast of Malabar:-
- Small botanical region – Cape Comorin to Gujarat and Western Ghat.
- Region of heavy rainfall.
- 4 types of forests:
i) Tropical forests:- 700 m altitude – tall trees, root buttresses – Artocarpus hirsuta.
ii) Mixed deciduous forests:- 1600 m – Terminalia spp., teak, bamboo.
iii) Temperate evergreen forests (sholas):- above 1200 m – Gardenia robtusa, Michelia nilgirica.
iv) Mangrove vegetation:- west coast of Malabar region – high rainfall.
8. Assam:-
- Rich in vegetation.
- Covers valley of Brahmaputra, Naga hills and Manipur.
- Heavy rainfall.
- Cherrapunji – one of the rainiest places in world – 1000 cm rainfall.
- Ficus, Artocarpus, Michelia.
- Orchids and ferns are rich in this region.
9. Bay Islands of Andaman and Nicobar:-
- Represent elevated portions of submarine mountains.
- Humid climate.
- In Andaman – beech forest, evergreen forest, semi-evergreen forest, deciduous forest and mangrove forest.
- Rhizophora, Mimusops are common.
- Some part is under cultivation – rice and sugarcane.