404
Study, further, revealed not much variations
in the species composition, but a change in the
bulk of different species, was discernible. The
2-m-depth zone recorded a monospecifi c stand
throughout the year consisting mainly of Najas
minor, Nelumbo nucifera, etc. However, Najas
minor, Ceratophyllum demersum and Hydrilla
verticillata were the perennial species (Unni
1972 ). Further, Cyperus alopecuroides and
Echinochloa crus-pavonis along with local
patches of Oryza rufi pogon, Eleocharis plantaginea and the pleustonic Eichhornia crassipes
develop along the very shallow eastern margin of
the lake when the water level starts rising in
June. Nymphaea cyanea generally comes up in
water level not >2m. Beyond it, Nelumbo
nucifera appears and may occupy the whole of
the deeper part of the basin. Further, patches of
Trapa bispinosa generally develop in water
which is 1–2.5 m deep.
AM succession has been recorded in this lake.
The monsoon varieties are succeeded by late
monsoon and winter varieties, notably
Limnophyton obtusifolium, fl oating mat of Azolla
pinnata, Spirodela polyrhiza and Pistia stratiotes. Subsequently, Nymphaea cyanea fl ourish
with fl owering and fruiting and then generally
degenerate. They are replaced by Nymphoides
cristatum, N. indicum, etc. Further, Nelumbo
nucifera seem to appear in deeper water. Further,
the leaves of Trapa fall off, might be due to
decrease in temperature. Eichhornia was found
to be wafted to the north side of the lake where it
may form a sudd for 2–3 months mainly due to
reduction in emergent and fl oating AM.
These observations refl ect that, in at least
small eutrophic lakes in the tropics, there is generally succession of one species by another during the annual seasonal cycle that occurs in
temperate latitudes.
In addition to the above, it had sometimes
been found that the marked seasonal variation in
water level generally produces another interesting feature in the cycle of vegetation. As the
water becomes increasingly shallow with the
change in seasons and dries up over the fl at eastern side of the basin, the newly exposed mud is
colonised by a characteristic eulittoral fl ora, in
which the composites Gnaphalium indicum and
Sphaeranthus indicus are important.
20.3.11 Wetlands of Odisha (Orissa)
The province of Odisha is blessed with a large
area of wetlands of different kinds. They include
the Chilika Lake, which is one of the largest
brackish water lakes in Asia. However, some of
the wetlands are discussed below.
20.3.11.1 Bhitarkanika Mangroves
These mangrove wetlands lie in the Odisha province of India. The wetland covers an area of
650 km
2 in the river delta of the Brahmani and
Baitarani rivers.
History
The Bhitarkanika Mangroves were Zamindari
forests till 1952. They were inducted in Forest
Department with the abolition of Zamindari system by the Government of Odisha. In 1975, an
area of 672 km
2 was declared as the Bhitarkanika
Wildlife Sanctuary. The core area of the sanctuary, with an area of 145 km
2
, was declared
Bhitarkanika National Park in September 1998.
Bhitarkanika Mangroves were designated as a
Ramsar wetland of international importance in
2002.
Ecology
The Bhitarkanika Mangroves are home to 55 of
India’s 58 known mangrove species. The mangroves harbour one of India’s largest populations
of saltwater crocodiles. Gahirmatha Beach is the
world’s most important nesting beach for olive
ridley sea turtles. The wetland also hosts a large
and diverse population of resident and migratory
birds.
20.3.11.2 Chilika Lake
It is one of the biggest brackish water lakes in
Asia. An account of this lake is given below.
Geography and Topography
Chilika Lake ( Chilka Lake ) lies at 0–2 m MSL,
between 19° 28′ and 19° 54′ N and 85° 6′ and 85°
20 Wetlands of India
Study, further, revealed not much variations
in the species composition, but a change in the
bulk of different species, was discernible. The
2-m-depth zone recorded a monospecifi c stand
throughout the year consisting mainly of Najas
minor, Nelumbo nucifera, etc. However, Najas
minor, Ceratophyllum demersum and Hydrilla
verticillata were the perennial species (Unni
1972 ). Further, Cyperus alopecuroides and
Echinochloa crus-pavonis along with local
patches of Oryza rufi pogon, Eleocharis plantaginea and the pleustonic Eichhornia crassipes
develop along the very shallow eastern margin of
the lake when the water level starts rising in
June. Nymphaea cyanea generally comes up in
water level not >2m. Beyond it, Nelumbo
nucifera appears and may occupy the whole of
the deeper part of the basin. Further, patches of
Trapa bispinosa generally develop in water
which is 1–2.5 m deep.
AM succession has been recorded in this lake.
The monsoon varieties are succeeded by late
monsoon and winter varieties, notably
Limnophyton obtusifolium, fl oating mat of Azolla
pinnata, Spirodela polyrhiza and Pistia stratiotes. Subsequently, Nymphaea cyanea fl ourish
with fl owering and fruiting and then generally
degenerate. They are replaced by Nymphoides
cristatum, N. indicum, etc. Further, Nelumbo
nucifera seem to appear in deeper water. Further,
the leaves of Trapa fall off, might be due to
decrease in temperature. Eichhornia was found
to be wafted to the north side of the lake where it
may form a sudd for 2–3 months mainly due to
reduction in emergent and fl oating AM.
These observations refl ect that, in at least
small eutrophic lakes in the tropics, there is generally succession of one species by another during the annual seasonal cycle that occurs in
temperate latitudes.
In addition to the above, it had sometimes
been found that the marked seasonal variation in
water level generally produces another interesting feature in the cycle of vegetation. As the
water becomes increasingly shallow with the
change in seasons and dries up over the fl at eastern side of the basin, the newly exposed mud is
colonised by a characteristic eulittoral fl ora, in
which the composites Gnaphalium indicum and
Sphaeranthus indicus are important.
20.3.11 Wetlands of Odisha (Orissa)
The province of Odisha is blessed with a large
area of wetlands of different kinds. They include
the Chilika Lake, which is one of the largest
brackish water lakes in Asia. However, some of
the wetlands are discussed below.
20.3.11.1 Bhitarkanika Mangroves
These mangrove wetlands lie in the Odisha province of India. The wetland covers an area of
650 km
2 in the river delta of the Brahmani and
Baitarani rivers.
History
The Bhitarkanika Mangroves were Zamindari
forests till 1952. They were inducted in Forest
Department with the abolition of Zamindari system by the Government of Odisha. In 1975, an
area of 672 km
2 was declared as the Bhitarkanika
Wildlife Sanctuary. The core area of the sanctuary, with an area of 145 km
2
, was declared
Bhitarkanika National Park in September 1998.
Bhitarkanika Mangroves were designated as a
Ramsar wetland of international importance in
2002.
Ecology
The Bhitarkanika Mangroves are home to 55 of
India’s 58 known mangrove species. The mangroves harbour one of India’s largest populations
of saltwater crocodiles. Gahirmatha Beach is the
world’s most important nesting beach for olive
ridley sea turtles. The wetland also hosts a large
and diverse population of resident and migratory
birds.
20.3.11.2 Chilika Lake
It is one of the biggest brackish water lakes in
Asia. An account of this lake is given below.
Geography and Topography
Chilika Lake ( Chilka Lake ) lies at 0–2 m MSL,
between 19° 28′ and 19° 54′ N and 85° 6′ and 85°
20 Wetlands of India