Flora of Mumbai-2

Continuing the tryst with Flora with an effort to understand Floristic biodiversity and landscape character, atleast three sources of information have been useful to view the Floristic composition of the landscape of the Mumbai region:

1. BOTANICAL REGION: A Botanical region is roughly similar to the geographical regions ( i.e. Malabar, Deccan, Gangetic Plains, Himalayan etc.) 
2. Forest Type of the Mumbai region (Forest Type– the coverage/ extent of any/ all floristic types.)
3. HISTORIC ACCOUNTS OF AGRICULTURAL AND HORTICULTURAL PRACTICES-  sourced from the Gazetteer of Bombay (SM Edwards 1909, Vol I pp 80- 125)

 FLORA OF MUMBAI- a brief summary:

With respect to the Botanical Regions of India, Mumbai comes under the Malabar region, which is continuous along the West Coast. This region is characterized by Tropical and Sub-Tropical Moist (Broadleaf) Forest type.

As per the eco-system classification of the Forest Types of India (Champion and Seth, 1931), the Mumbai region is dominated by the Sub-Tropical Moist Deciduous Forest type.

A study of the recordings in the Gazetteer of Bombay  (Vol I pp 80- 125  ) indicates a large portion of the natural landscape of the Bombay region having characteristics of a seasonal and Littoral Swamp- which is a different Forest Type.

The Manmade landscape of the erstwhile Bombay region is also recorded as a mixed palette of Horticultural practices –introduction of exotic/ non-native plant species (now naturalized), Fruit Orchards and Vegetable farming. 

The average rainfall of Mumbai - 2300 mm- coupled with its subtropical climate can sustain a broad palette of plant material, including exotics. In order to conserve the amount of water used in landscape irrigation and address native plant diversity, the preference of native and naturalized species over exotics, plays an important role. The Botanical diversity of the Mumbai region has some common parameters. 

	BOTANICAL REGION	FOREST TYPE
Native Forest Type	Tropical and Sub-Tropical Moist (Broadleaf) Forest	Sub-Tropical    Moist Deciduous	Tropical Seasonal  Swamp Forest
Mean Annual Rainfall	1200-3000	1900- 3000 mm	1000-2000 mm
# of Rainy Days	63-150	100-110	~ 100
# of Dry Months	3-8 months	4-6	4-6 months
Annual Mean Humidity	Upto 80%	80%	>80 %
Mean Annual Temp	24-27 C	Upto 30 C	Upto 30 C
Mean Maximum Temp	43C	40 C- 43C	-------
Natural water availability (rainfall) /natural irrigation rate	Approx 30 mm per day for 100 days	Approx 30 mm per  dayfor 100 days	Approx 20 mm per  dayfor 100 days
Species Natural Occurrence:	Albizzia spp. Dendrocalamus strictus (bamboo) Lagerstroemia spp. Mimusops elengi Schleichera trijuga Tectona grandis (teak) 10-25% Terminalia spp. Zizyphus jujuba	Atrocarpus spp. Albizzia spp. Amoora rohituka Anona spp. Eugenia spp. Michelia spp. Terminalia spp.	Borasus flabellifer Cocos nucifera Phoenix sylvestris Syzygium cumini   Mangrove scrub  Acanthus spp.  Avicennia spp.  Salvadora persica

 ISSUE:

Current horticultural practice is to provide between 4 to 6 litres per sq.mt of water during establishment and reducing to approx 3-4 litres thereon. This is due to the predominant use of lawns, exotic plants, and the urge to have a manicured look.

Compare this statistic to the natural water availability in the table above.  

LESSON:

If the Mean annual rainfall is taken as the optimum water requirement for the planting, then from this, the daily water requirement can be calculated. Due to the naturalization of these species, their ability to cope with dry spells is much more than exotics. This further reduces the daily demand for water.