276
1998). Some of the important physico-chemical
characteristics of water and soil of the freshwater swamps are as follows:
(a) They are generally acidic to circum-neutral
depending on the accumulation of peat.
(b) Nutrient and mineral contents may be rich or
poor. This depends on whether these are
rainwater- fed swamps or groundwater discharge swamps.
(c) An alluvial river swamp may often show a
water quality which could be quite different
from that of the adjacent river.
Notwithstanding the above, many FW
swamps, specially the alluvial river swamps, are
open to river fl ooding and other inputs of neutral
and generally well-mineralised waters. However,
the buffering capacity of the water in cypress
swamps is generally low. Little or no alkalinity
and low concentration of dissolved ions and
nutrients are some of the signifi cant features of
precipitation-dominated swamps, like the
cypress domes.
18.8.7 Ecosystem Structure
18.8.7.1 Vegetation
Plant communities which either depend on or
adapt to the almost continuously wet environment are generally found in the southern deepwater swamps, like the cypress wetlands. The
dominant canopy vegetation found in alluvial
river swamps of the SE USA includes bald
cypress ( Taxodium distichum ) and water tupelo
( Nyssa aquatica ). Many of the pure tupelo stands
are thought to be the result of the selective logging of bald cypress (Penfound 1952).
18.8.7.2 Fire
Fire is generally infrequent in swamps because of
the standing water. But it could be a signifi cant
ecological factor during droughts or in swamps
which have been artifi cially drained. However , it
is generally more frequent in the forested
swamps, say in Florida. This could be because of
quite frequent lightning storms and relatively
longer dry season (Motzkin et al. 1993).
18.8.7.3 Consumers
Populations of invertebrates, particularly of the
benthic macro-invertebrates, have been analysed
in a number of cypress–tupelo swamps. A rich
diversity and signifi cant number of invertebrates
have been found in permanently fl ooded swamps.
The species include crayfi sh, clams, oligochaete
worms, snails, freshwater shrimp, midges and
amphipods (Beck 1977).
18.8.7.4 Fish
Fish are both temporary and permanent residents
of alluvial river swamps (Wharton et al. 1976,
1981). A number of studies recorded the value of
sloughs and backswamps for fi sh and shellfi sh
spawning and feeding during the fl ooding season
(Lambou 1965, 1990). Further, the deepwater
swamps often serve as reservoir for fi sh when
fl ooding ceases, although the backwaters are less
than optimum for aquatic life because of fl uctuating water levels and occasional low DO levels.
Several species of forage minnows often dominate alluvial river swamps where most larger
fi shes are temporary residents of the wetlands
(Clark 1979).
18.8.7.5 Amphibians and Reptiles
Amphibians and reptiles occur in swamps mainly
because of their ability to adapt to fl uctuating
water levels. Nine to ten species of frogs are
common in many SE cypress–gum swamps
(Clark 1979).
18.8.8 Ecosystem Function
(a) Swamp productivity is closely linked to its
hydrologic regime.
(b) Swamps may be nutrient sinks whether the
nutrients are a natural source or are artifi -
cially applied. The function of forested
wetlands as nutrient sinks was suggested by
Kitchens et al. (1975).
(c) Decomposition of woody and nonwoody
material in swamps is affected by the
water regime and the subsequent degree of
anaerobiosis.
18 Classifi cation of Wetlands
1998). Some of the important physico-chemical
characteristics of water and soil of the freshwater swamps are as follows:
(a) They are generally acidic to circum-neutral
depending on the accumulation of peat.
(b) Nutrient and mineral contents may be rich or
poor. This depends on whether these are
rainwater- fed swamps or groundwater discharge swamps.
(c) An alluvial river swamp may often show a
water quality which could be quite different
from that of the adjacent river.
Notwithstanding the above, many FW
swamps, specially the alluvial river swamps, are
open to river fl ooding and other inputs of neutral
and generally well-mineralised waters. However,
the buffering capacity of the water in cypress
swamps is generally low. Little or no alkalinity
and low concentration of dissolved ions and
nutrients are some of the signifi cant features of
precipitation-dominated swamps, like the
cypress domes.
18.8.7 Ecosystem Structure
18.8.7.1 Vegetation
Plant communities which either depend on or
adapt to the almost continuously wet environment are generally found in the southern deepwater swamps, like the cypress wetlands. The
dominant canopy vegetation found in alluvial
river swamps of the SE USA includes bald
cypress ( Taxodium distichum ) and water tupelo
( Nyssa aquatica ). Many of the pure tupelo stands
are thought to be the result of the selective logging of bald cypress (Penfound 1952).
18.8.7.2 Fire
Fire is generally infrequent in swamps because of
the standing water. But it could be a signifi cant
ecological factor during droughts or in swamps
which have been artifi cially drained. However , it
is generally more frequent in the forested
swamps, say in Florida. This could be because of
quite frequent lightning storms and relatively
longer dry season (Motzkin et al. 1993).
18.8.7.3 Consumers
Populations of invertebrates, particularly of the
benthic macro-invertebrates, have been analysed
in a number of cypress–tupelo swamps. A rich
diversity and signifi cant number of invertebrates
have been found in permanently fl ooded swamps.
The species include crayfi sh, clams, oligochaete
worms, snails, freshwater shrimp, midges and
amphipods (Beck 1977).
18.8.7.4 Fish
Fish are both temporary and permanent residents
of alluvial river swamps (Wharton et al. 1976,
1981). A number of studies recorded the value of
sloughs and backswamps for fi sh and shellfi sh
spawning and feeding during the fl ooding season
(Lambou 1965, 1990). Further, the deepwater
swamps often serve as reservoir for fi sh when
fl ooding ceases, although the backwaters are less
than optimum for aquatic life because of fl uctuating water levels and occasional low DO levels.
Several species of forage minnows often dominate alluvial river swamps where most larger
fi shes are temporary residents of the wetlands
(Clark 1979).
18.8.7.5 Amphibians and Reptiles
Amphibians and reptiles occur in swamps mainly
because of their ability to adapt to fl uctuating
water levels. Nine to ten species of frogs are
common in many SE cypress–gum swamps
(Clark 1979).
18.8.8 Ecosystem Function
(a) Swamp productivity is closely linked to its
hydrologic regime.
(b) Swamps may be nutrient sinks whether the
nutrients are a natural source or are artifi -
cially applied. The function of forested
wetlands as nutrient sinks was suggested by
Kitchens et al. (1975).
(c) Decomposition of woody and nonwoody
material in swamps is affected by the
water regime and the subsequent degree of
anaerobiosis.
18 Classifi cation of Wetlands