48
both the % and the amount of exchangeable
hydrogen ions increase as organic content
increases. Incidentally, the high cation capacity
for sphagnum moss peat is caused by long-chain
polymers of uronic acid (Clymo 1983).
4.2
Organic Soils
(Organic Wetland Soil)
The remains of plants in various stages of
decomposition primarily composes the organic
soil. This accumulates in the wetlands as a result
of anaerobic conditions created by standing
water or poorly drained conditions. Two of the
more important characteristics of organic soil,
namely, peat and muck, are botanical in origin
(Clymo 1983).
4.2.1 Botanical Origin
The botanical origin of organic material could be:
(a) Mosses,
(b) herbaceous material,
(c) wood and leaf litter
Organic soils may originate from herbaceous
grasses, such as reed grass (Phragmites) and wild
rice (Zizania). Organic soils may also be produced in freshwater marshes by plant fragments
from a number of non-grass plants, e.g. Typha
and Nymphaea.
4.2.1.1 Decomposition
One of the key characteristics of organic peat is
the state of decomposition or humification of
wetland soils. The original plant structure is
altered physically and chemically as decomposition proceeds until the resulting material little
resembles the parent material.
Notwithstanding the above, organic soils (histosols) are classified into four groups as follows:
(a) ‘Saprists’ (muck): Two-thirds or more of the
material is decomposed and
(b) ‘Fibrists’ (peat):
fibres are identifiable.
(c) ‘Hemists’ (mucky-peat of peaty-muck):
Conditions fall between saprist and fibrist soil.
(d) ‘Folists’: Organic soils caused by excessive
moisture.
Further, organic soils are generally dark in
colour.
An account of the peat-forming mires is given
below:
Peat-forming mires are most typical of high
latitudes. Here, low temperature limits both evaporation and microbial respiration. The circumstances of peat formation are three-fold (Moore
and Bellamy 1973). Notwithstanding the above,
in extremely wet soils, organic matter accumulates faster than microbial respiration can dispose
it off. This may create organic peat soils or histosols which is an azonal group that occurs anywhere and without any necessary relationship to
surrounding zonal soil types. These peats are,
generally, strongly acid peat formers, such as
sphagnum moss species, plants belonging to
Cyperaceae and some grasses. Neutral and mildly
alkaline peats are associated with fen vegetation.
This fen, at its richest, is a species-diverse luxuriant herbaceous ecosystem which intergrades
through a more acid, calcium-deficient poor fen
to acid peat bog vegetation. In late succession,
organic fen peats become colonised by floodtolerant trees and shrubs, which characteristically
include the alders and willows in North America
and Eurasia.
Primary peats are those which are formed in
hollows which receive drainage water, and the
accumulation of the peat actually reduces the
water capacity of the basin. Secondary peats
develop from primary by over- spillage of the
growing peat onto surfaces adjacent to the primary basin. Tertiary peats are independent of a
pre-existing drainage basin and are formed on
any level or gently sloping surface when precipitation substantially exceeds evaporation.
Secondary peats are similar to the primary
peats with which they are associated. They
remain in capillary contact with the underlying
soil solution but with a sufficiently high precipitation–evaporation (P/E) ratio. Tertiary peat
growth involves loss of hydrological contact with
underlying system.
4 Lentic Soil or Mud (Physico-chemical Characteristics of Soil)
both the % and the amount of exchangeable
hydrogen ions increase as organic content
increases. Incidentally, the high cation capacity
for sphagnum moss peat is caused by long-chain
polymers of uronic acid (Clymo 1983).
4.2
Organic Soils
(Organic Wetland Soil)
The remains of plants in various stages of
decomposition primarily composes the organic
soil. This accumulates in the wetlands as a result
of anaerobic conditions created by standing
water or poorly drained conditions. Two of the
more important characteristics of organic soil,
namely, peat and muck, are botanical in origin
(Clymo 1983).
4.2.1 Botanical Origin
The botanical origin of organic material could be:
(a) Mosses,
(b) herbaceous material,
(c) wood and leaf litter
Organic soils may originate from herbaceous
grasses, such as reed grass (Phragmites) and wild
rice (Zizania). Organic soils may also be produced in freshwater marshes by plant fragments
from a number of non-grass plants, e.g. Typha
and Nymphaea.
4.2.1.1 Decomposition
One of the key characteristics of organic peat is
the state of decomposition or humification of
wetland soils. The original plant structure is
altered physically and chemically as decomposition proceeds until the resulting material little
resembles the parent material.
Notwithstanding the above, organic soils (histosols) are classified into four groups as follows:
(a) ‘Saprists’ (muck): Two-thirds or more of the
material is decomposed and
(b) ‘Fibrists’ (peat):
fibres are identifiable.
(c) ‘Hemists’ (mucky-peat of peaty-muck):
Conditions fall between saprist and fibrist soil.
(d) ‘Folists’: Organic soils caused by excessive
moisture.
Further, organic soils are generally dark in
colour.
An account of the peat-forming mires is given
below:
Peat-forming mires are most typical of high
latitudes. Here, low temperature limits both evaporation and microbial respiration. The circumstances of peat formation are three-fold (Moore
and Bellamy 1973). Notwithstanding the above,
in extremely wet soils, organic matter accumulates faster than microbial respiration can dispose
it off. This may create organic peat soils or histosols which is an azonal group that occurs anywhere and without any necessary relationship to
surrounding zonal soil types. These peats are,
generally, strongly acid peat formers, such as
sphagnum moss species, plants belonging to
Cyperaceae and some grasses. Neutral and mildly
alkaline peats are associated with fen vegetation.
This fen, at its richest, is a species-diverse luxuriant herbaceous ecosystem which intergrades
through a more acid, calcium-deficient poor fen
to acid peat bog vegetation. In late succession,
organic fen peats become colonised by floodtolerant trees and shrubs, which characteristically
include the alders and willows in North America
and Eurasia.
Primary peats are those which are formed in
hollows which receive drainage water, and the
accumulation of the peat actually reduces the
water capacity of the basin. Secondary peats
develop from primary by over- spillage of the
growing peat onto surfaces adjacent to the primary basin. Tertiary peats are independent of a
pre-existing drainage basin and are formed on
any level or gently sloping surface when precipitation substantially exceeds evaporation.
Secondary peats are similar to the primary
peats with which they are associated. They
remain in capillary contact with the underlying
soil solution but with a sufficiently high precipitation–evaporation (P/E) ratio. Tertiary peat
growth involves loss of hydrological contact with
underlying system.
4 Lentic Soil or Mud (Physico-chemical Characteristics of Soil)