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19.1 Introduction
Mangroves are assemblages of salt tolerant shrubs and trees (also called hydrophytes) that grow along the inter-tidal regions in the form of narrow strips or as
extensive patches in estuarine habitats and river deltas of tropical and sub-tropical
coastal areas. The term “mangrove” originated from the Portuguese and English
words ‘Mangue’ and ‘Grove’. These two words mean ‘mangrove plants’ and ‘group
of trees’ respectively. The term ‘mangrove’ is, thus representative of a single plant
as well as a plant community. MacNae (1968) proposed ‘mangal’ as a term for the
community, leaving “mangrove” for the constituent plant species.
The term ‘mangrove’ describes both the ecosystem and the plant families that
have developed specialized adaptations to live in the tidal environment. Majority of
plants are evergreen trees, although deciduous trees, perennial and evergreen shrubs,
parasites and climbers, perennial grasses and perennial ferns are also common constituents of this ecosystem together with algae and fungi (Tomlinson 1986).
Recently, Mukherjee et al. (2014) have arrived at the following definition of
mangrove through consensus: Mangroves are woody plants that grow normally in
the tropical and sub-tropical latitudes along the land- sea interface, bays, estuaries,
lagoons and back waters. These plants and their associated organisms constitute the
“mangrove forest” or “mangal”. The mangal and its associated abiotic factors constitute the “mangrove ecosystem”.
Mangroves occur world-wide in the tropics and subtropics, mainly between
32°N and 38°S latitudes. Sheltered environment with brackish water influx, estuarine and deltaic muddy soil, good rainfall (1000–3000 mm) and temperature
between 26 and 35° C are considered as ideal habitat for luxuriant growth of
mangroves.
In comparison to terrestrial forests, the structure of the mangrove forests appears
to be relatively simple as the forest canopy cover, usually comprises of the main
branches and leaves of the trees, and there are few smaller plants on the floor of the
forest (Kathiresan and Bingham 2001). The vines and shrubs common to the most
of the tropical terrestrial forests are missing in case of mangrove forests, though
there is often a carpet of mangrove seedlings present. The missing understory, in
case of mangrove forests, is basically due to the prevailing harsh conditions and the
lack of presence of light.
To survive in harsh coastal conditions, mangrove plants exhibit a wide variety of
adaptations in terms of morphology, physiology, anatomy, physiognomy, development of seed and seedlings, sclerophyllous leaves with sunken stomata, and vivipary
are some of the common adaptations. The roots possess pneumatopores or lenticels
for the purpose of gaseous exchange. Exclusion of salt through rhizo-filtration,
excretion of salts through salt glands, and the ability to deposit salt in older leaves,
barks and pneumatophores help the plants to acquire high level of salt tolerance
(Tomlinson 1986). The control of tissue water potential is done through specialized
leaves and stems.
Ajai and H.B. Chauhan
19.1 Introduction
Mangroves are assemblages of salt tolerant shrubs and trees (also called hydrophytes) that grow along the inter-tidal regions in the form of narrow strips or as
extensive patches in estuarine habitats and river deltas of tropical and sub-tropical
coastal areas. The term “mangrove” originated from the Portuguese and English
words ‘Mangue’ and ‘Grove’. These two words mean ‘mangrove plants’ and ‘group
of trees’ respectively. The term ‘mangrove’ is, thus representative of a single plant
as well as a plant community. MacNae (1968) proposed ‘mangal’ as a term for the
community, leaving “mangrove” for the constituent plant species.
The term ‘mangrove’ describes both the ecosystem and the plant families that
have developed specialized adaptations to live in the tidal environment. Majority of
plants are evergreen trees, although deciduous trees, perennial and evergreen shrubs,
parasites and climbers, perennial grasses and perennial ferns are also common constituents of this ecosystem together with algae and fungi (Tomlinson 1986).
Recently, Mukherjee et al. (2014) have arrived at the following definition of
mangrove through consensus: Mangroves are woody plants that grow normally in
the tropical and sub-tropical latitudes along the land- sea interface, bays, estuaries,
lagoons and back waters. These plants and their associated organisms constitute the
“mangrove forest” or “mangal”. The mangal and its associated abiotic factors constitute the “mangrove ecosystem”.
Mangroves occur world-wide in the tropics and subtropics, mainly between
32°N and 38°S latitudes. Sheltered environment with brackish water influx, estuarine and deltaic muddy soil, good rainfall (1000–3000 mm) and temperature
between 26 and 35° C are considered as ideal habitat for luxuriant growth of
mangroves.
In comparison to terrestrial forests, the structure of the mangrove forests appears
to be relatively simple as the forest canopy cover, usually comprises of the main
branches and leaves of the trees, and there are few smaller plants on the floor of the
forest (Kathiresan and Bingham 2001). The vines and shrubs common to the most
of the tropical terrestrial forests are missing in case of mangrove forests, though
there is often a carpet of mangrove seedlings present. The missing understory, in
case of mangrove forests, is basically due to the prevailing harsh conditions and the
lack of presence of light.
To survive in harsh coastal conditions, mangrove plants exhibit a wide variety of
adaptations in terms of morphology, physiology, anatomy, physiognomy, development of seed and seedlings, sclerophyllous leaves with sunken stomata, and vivipary
are some of the common adaptations. The roots possess pneumatopores or lenticels
for the purpose of gaseous exchange. Exclusion of salt through rhizo-filtration,
excretion of salts through salt glands, and the ability to deposit salt in older leaves,
barks and pneumatophores help the plants to acquire high level of salt tolerance
(Tomlinson 1986). The control of tissue water potential is done through specialized
leaves and stems.
Ajai and H.B. Chauhan