212
Accordingly, they have characteristics of both the
systems. However, there are some major differences between wetlands and drier upland ecosystems. In the wetlands, more nutrients are tied up
in organic deposits and are lost from the ecosystem cycling as peat deposits or organic exports.
Further, wetlands are more frequently open to
nutrient fluxes than the upland ecosystems. As
such, they may not be much dependent on the
recycling of nutrients. However, wetlands, which
are not open to these fluxes, often have lower productivities and slower nutrient cycling than comparable upland ecosystems.
Concomitant to above, wetlands are similar to
deep aquatic ecosystems, in that most of the
nutrients are primarily tied up in sediments and
peats. In most deep aquatic systems, the retention
of nutrients in organic sediments is probably longer than in wetlands. However, wetlands usually
involve larger biotic storages of nutrients than do
deep aquatic ecosystems, which are primarily
plankton dominated.
Further, another important difference between
wetlands and lakes is that most wetland plants
obtain their nutrients from the sediments, whereas
phytoplankton depends on nutrients dissolved in
the water column. Wetland plants have often been
called ‘nutrient pumps’, which bring nutrients
from the anaerobic sediments to the above- ground
strata. On the other hand, phytoplankton in lakes
could be viewed as ‘nutrient dumps’ which take
nutrients out of the aerobic zone and, through settling and death, deposit the nutrients in the anaerobic sediments. Thus, the plants in these two
environments could be viewed as having decidedly different functions in nutrient cycling.
Summary
1. Wetland biogeochemical cycles feature a
blending of chemical transformation and
chemical transport processes which are, perhaps, not shared by many other ecosystems.
2. The transport and transformation of chemicals in ecosystems is known as biogeochemical cycle. It involves a great number of
interrelated physical, chemical and biological
processes.
3. The biogeochemical processes are markedly
influenced by the unique and diverse hydrologic conditions in wetlands. These processes lead to changes in the chemical forms
of materials within wetlands. Also, these
processes, in turn, play roles to determine the
overall wetland productivity.
4. The biogeochemistry of wetlands could be
divided into two broad aspects, namely, (1)
intra-system cycling through various transformation processes and (2) the exchange of
chemicals between a wetland and its surroundings. The wetland soils are important
media, in which many of the wetland chemical transformations take place.
5. The remains of plants in various stages of
decomposition primarily compose the
organic soil. On the other hand, mineral soils
develop certain characteristics when flooded
for extended periods. This helps in their
identification.
6. Further, organic soils are different from
mineral soils in a number of physico-chemical features other than the % of OC.
Anaerobic conditions usually result when
soils (whether mineral or organic) are inundated with water.
7. Redox potential or oxidation–reduction
potential is a measure of the electron pressure (or availability) in a solution.
8. Nitrogen often is one of the most limiting
nutrients in flooded soils. Microbial denitrification of nitrates to gaseous form of nitrogen
in wetlands and their subsequent release to the
atmosphere remain one of the more significant ways, in which nitrogen is lost from the
lithosphere and hydrosphere to the
atmosphere.
9. However, the reduction of Mn and Fe comes
below the reduction of nitrate on the redox
potential scale. Fe and Mn are found in wetlands primarily in their reduced forms. In
wetlands, sulphur occurs in several different
states of oxidation. It is transformed through
several pathways like nitrogen. These are
mediated by microbes. Further, in wetlands,
sulphur is rarely present in such low concen13 Wetland Biogeochemistry
Accordingly, they have characteristics of both the
systems. However, there are some major differences between wetlands and drier upland ecosystems. In the wetlands, more nutrients are tied up
in organic deposits and are lost from the ecosystem cycling as peat deposits or organic exports.
Further, wetlands are more frequently open to
nutrient fluxes than the upland ecosystems. As
such, they may not be much dependent on the
recycling of nutrients. However, wetlands, which
are not open to these fluxes, often have lower productivities and slower nutrient cycling than comparable upland ecosystems.
Concomitant to above, wetlands are similar to
deep aquatic ecosystems, in that most of the
nutrients are primarily tied up in sediments and
peats. In most deep aquatic systems, the retention
of nutrients in organic sediments is probably longer than in wetlands. However, wetlands usually
involve larger biotic storages of nutrients than do
deep aquatic ecosystems, which are primarily
plankton dominated.
Further, another important difference between
wetlands and lakes is that most wetland plants
obtain their nutrients from the sediments, whereas
phytoplankton depends on nutrients dissolved in
the water column. Wetland plants have often been
called ‘nutrient pumps’, which bring nutrients
from the anaerobic sediments to the above- ground
strata. On the other hand, phytoplankton in lakes
could be viewed as ‘nutrient dumps’ which take
nutrients out of the aerobic zone and, through settling and death, deposit the nutrients in the anaerobic sediments. Thus, the plants in these two
environments could be viewed as having decidedly different functions in nutrient cycling.
Summary
1. Wetland biogeochemical cycles feature a
blending of chemical transformation and
chemical transport processes which are, perhaps, not shared by many other ecosystems.
2. The transport and transformation of chemicals in ecosystems is known as biogeochemical cycle. It involves a great number of
interrelated physical, chemical and biological
processes.
3. The biogeochemical processes are markedly
influenced by the unique and diverse hydrologic conditions in wetlands. These processes lead to changes in the chemical forms
of materials within wetlands. Also, these
processes, in turn, play roles to determine the
overall wetland productivity.
4. The biogeochemistry of wetlands could be
divided into two broad aspects, namely, (1)
intra-system cycling through various transformation processes and (2) the exchange of
chemicals between a wetland and its surroundings. The wetland soils are important
media, in which many of the wetland chemical transformations take place.
5. The remains of plants in various stages of
decomposition primarily compose the
organic soil. On the other hand, mineral soils
develop certain characteristics when flooded
for extended periods. This helps in their
identification.
6. Further, organic soils are different from
mineral soils in a number of physico-chemical features other than the % of OC.
Anaerobic conditions usually result when
soils (whether mineral or organic) are inundated with water.
7. Redox potential or oxidation–reduction
potential is a measure of the electron pressure (or availability) in a solution.
8. Nitrogen often is one of the most limiting
nutrients in flooded soils. Microbial denitrification of nitrates to gaseous form of nitrogen
in wetlands and their subsequent release to the
atmosphere remain one of the more significant ways, in which nitrogen is lost from the
lithosphere and hydrosphere to the
atmosphere.
9. However, the reduction of Mn and Fe comes
below the reduction of nitrate on the redox
potential scale. Fe and Mn are found in wetlands primarily in their reduced forms. In
wetlands, sulphur occurs in several different
states of oxidation. It is transformed through
several pathways like nitrogen. These are
mediated by microbes. Further, in wetlands,
sulphur is rarely present in such low concen13 Wetland Biogeochemistry