Acrotelm Catotelm on:
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The acrotelm is one of two distinct layers in undisturbed
Fluctuations in the position of the water table in a peat bog occur within the acrotelm, and hence conditions may vary from aerobic to anaerobic with time.
Where there are extensive geological fluctuations in the peatland surface, the depth of the acrotelm may change fundamentally over a couple of meters of distance. In general, the acrotelm has a higher hydraulic conductivity and a lower bulk density than the catotelm. Other characteristics are shared by these two zones.
Completely developed acrotelm, only found in
peat bog
A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muske ...
s. It overlies the catotelm. The boundary between the two layers is defined by the transition from peat
Peat is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. ''Sphagnum'' moss, also called peat moss, is one of the most ...
containing living plants (acrotelm) to peat containing dead plant material (catotelm). This typically coincides with the lowest level of the water table
The water table is the upper surface of the phreatic zone or zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, which may be fresh, saline, or brackish, depending on the loc ...
. To lower the water table before harvesting, ditching
In aviation, a water landing is, in the broadest sense, an aircraft landing on a body of water. Seaplanes, such as floatplanes and flying boats, land on water as a normal operation. Ditching is a controlled emergency landing on the water sur ...
is performed first.
Natural peatlands
Fluctuations in the position of the water table in a peat bog occur within the acrotelm, and hence conditions may vary from aerobic to anaerobic with time.
Where there are extensive geological fluctuations in the peatland surface, the depth of the acrotelm may change fundamentally over a couple of meters of distance. In general, the acrotelm has a higher hydraulic conductivity and a lower bulk density than the catotelm. Other characteristics are shared by these two zones.
Mined peatlands
After ditching, the acrotelm becomes thicker and more effective, drying the peat and simplifying harvesting. Drainage andsubsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...
lower the elevation of the peat surface, significantly lowering the soil's hydraulic conductivity
In science and engineering, hydraulic conductivity (, in SI units of meters per second), is a property of porous materials, soils and Rock (geology), rocks, that describes the ease with which a fluid (usually water) can move through the porosity, ...
.
Importance of atmospheric deposition
Completely developed acrotelm, only found in ombrotrophic
Ombrotrophic ("cloud-fed"), from Ancient Greek ὄμβρος (''ómvros'') meaning "rain" and τροφή (''trofí'') meaning "food"), refers to Soil, soils or vegetation which receive all of their water and nutrients from precipitation, rather ...
bogs, make it possible to study atmospheric deposition and how it affects ecosystems. Through the relatively quick disintegration of the acrotelm, only a small portion of the total nutrients locked up in the plant material are mineralized, making them available for additional plant development inclusive of bacterial and fungal activity.
See also
*Mire
A peatland is a type of wetland whose soils consist of Soil organic matter, organic matter from decaying plants, forming layers of peat. Peatlands arise because of incomplete decomposition of organic matter, usually litter from vegetation, du ...
* Raised bog
Raised bogs, also called ombrotrophic bogs, are acidic, wet habitats that are poor in mineral salts and are home to flora and fauna that can cope with such extreme conditions. Raised bogs, unlike fens, are exclusively fed by precipitation (ombro ...
* Swamp
A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
References
{{Hydrology-stub Bogs Pedology