265
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_18, © Springer India 2013
18.1 Wetlands from Tropic
to Temperate
Wetlands have a worldwide similarity which
crosses the climate bar. This is in contrast to
vegetation of well-drained soils. Various parameters are used for the classifi cation of wetlands.
Aquatic plants are signifi cant components of a
wetland ecosystem, and they are often considered
in the classifi cation of wetlands. The wetlands
often harbour a rich diversity of aquatic plants.
Nevertheless, sometimes, the wetlands present a
hostile chemical environment which the plant
roots have to endure much. The constituent species generally possess morphological, anatomical
and physiological adaptations which permit them
to adapt with the frequent fl ooding, lack of dissolved oxygen and the resulting chemical reduction of the soil. Regular fl ooding may also limit
many large herbivores. In temperate climate, the
accessibility may be refl ected amongst the reed
swamps. Consequently, there will be less grazing
pressure compared to dry land pastures.
Aquatic littoral habitats are associated with
the static water of lakes and ponds. On the other
hand, the lotic system is associated with the riverside situations. The most widespread vegetation
generally belongs to the families of monocotyledons, e.g. the Cyperaceae, Poaceae and
Sparganiaceae. They are found to a big extent in
some parts of the world, e.g. 150,000 km
2 in the
Sudd of the upper Nile and >10,000 km
2 in the
Botswana Okovanggo. The great reed swamp
tract of the Camargue has largely been drained
for rice and other crop production in Europe.
Slow-fl owing rivers and streams, which are
fringed by a reed swamp, are, more or less, indistinguishable from that of still waters. Faster- fl owing
headwaters and immature rivers of unpredictable
catchments often lack any specialised riverine
vegetation.
Nutrient-rich groundwater mires ( valley mires )
may carry a species-rich fen vegetation. It intergrades with the wet health of oligotrophic
groundwater mires. Conversely, rainfed peatlands ( blanket mires and raised mires ) are generally acid, mineral defi cient. They are vegetated
with poor biomass, in which the bog mosses
( Sphagnum spp.) play a prominent role. It may be
noted that, in the tropics, peats may carry a reed
swamp–fen, riverine swamp forest or, in the case
of rainfed peat, a species-poor swamp forest.
Rice ( Oryza sativa ) is a domesticated tropical
reed swamp grass, and more than half of the
world’s population is supported by rice. Large
quantity of rice is produced through paddy culture in which the young seedlings are planted into
shallow water by fl ooding a previously cultivated, usually green manured soil. Its varieties
range from deepwater ‘fl oating’ rice to up land
rice which are never fl ooded.
The wetland varieties are, probably, the most
waterlogging tolerant of all plants because the
organically rich, microbially active wetland
soils generally produce extremes of anoxia and
chemical reduction.
18
Classifi cation of Wetlands
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_18, © Springer India 2013
18.1 Wetlands from Tropic
to Temperate
Wetlands have a worldwide similarity which
crosses the climate bar. This is in contrast to
vegetation of well-drained soils. Various parameters are used for the classifi cation of wetlands.
Aquatic plants are signifi cant components of a
wetland ecosystem, and they are often considered
in the classifi cation of wetlands. The wetlands
often harbour a rich diversity of aquatic plants.
Nevertheless, sometimes, the wetlands present a
hostile chemical environment which the plant
roots have to endure much. The constituent species generally possess morphological, anatomical
and physiological adaptations which permit them
to adapt with the frequent fl ooding, lack of dissolved oxygen and the resulting chemical reduction of the soil. Regular fl ooding may also limit
many large herbivores. In temperate climate, the
accessibility may be refl ected amongst the reed
swamps. Consequently, there will be less grazing
pressure compared to dry land pastures.
Aquatic littoral habitats are associated with
the static water of lakes and ponds. On the other
hand, the lotic system is associated with the riverside situations. The most widespread vegetation
generally belongs to the families of monocotyledons, e.g. the Cyperaceae, Poaceae and
Sparganiaceae. They are found to a big extent in
some parts of the world, e.g. 150,000 km
2 in the
Sudd of the upper Nile and >10,000 km
2 in the
Botswana Okovanggo. The great reed swamp
tract of the Camargue has largely been drained
for rice and other crop production in Europe.
Slow-fl owing rivers and streams, which are
fringed by a reed swamp, are, more or less, indistinguishable from that of still waters. Faster- fl owing
headwaters and immature rivers of unpredictable
catchments often lack any specialised riverine
vegetation.
Nutrient-rich groundwater mires ( valley mires )
may carry a species-rich fen vegetation. It intergrades with the wet health of oligotrophic
groundwater mires. Conversely, rainfed peatlands ( blanket mires and raised mires ) are generally acid, mineral defi cient. They are vegetated
with poor biomass, in which the bog mosses
( Sphagnum spp.) play a prominent role. It may be
noted that, in the tropics, peats may carry a reed
swamp–fen, riverine swamp forest or, in the case
of rainfed peat, a species-poor swamp forest.
Rice ( Oryza sativa ) is a domesticated tropical
reed swamp grass, and more than half of the
world’s population is supported by rice. Large
quantity of rice is produced through paddy culture in which the young seedlings are planted into
shallow water by fl ooding a previously cultivated, usually green manured soil. Its varieties
range from deepwater ‘fl oating’ rice to up land
rice which are never fl ooded.
The wetland varieties are, probably, the most
waterlogging tolerant of all plants because the
organically rich, microbially active wetland
soils generally produce extremes of anoxia and
chemical reduction.
18
Classifi cation of Wetlands