Marsh
A marsh, or morass, is a type of wetland characterized by being intermittently or continuously flooded with water that is not deep and with predominately soft-stemmed vegetation, such as grasses and sedges, that are adapted to conditions of saturated soil. The water of a marsh can be fresh, brackish, or saline. Like swamps, a marsh generally is considered to be a wetland that does not accumulate substantial peat deposits (NSC 2005).
In North America, marshes usually are regarded as wetlands dominated by soft-stemmed vegetation, while swamps usually are regarded as wetlands dominated by woody vegetation, such as trees and woody bushes (EPA 2004; NSC 2005). However, this distinction does not necessarily apply in other areas; for instance, in Africa swamps may be dominated by papyrus.
Elsewhere, a marsh is distinguished from a swamp by being a wetland with less open water surface and shallower water than a swamp.
Historically, salt marshes have sometimes been treated as "wastelands", along with other wetlands.
Marshes are critically important wildlife habitats, often serving as breeding grounds for a wide variety of animal life.
Constructed wetlands featuring surface-flow design are usually in the form of a marsh.
Definition and geology
A marsh is a type of wetland. A wetland is a transitional environment between permanently aquatic and terrestrial environments that shares characteristics of both environments and where water, which covers the soil or is near the surface for substantial parts of the year, is the key factor in determining the nature of the ecosystem and soil. Although wetlands have aspects similar to both wet and and dry environments, they cannot be classified unambiguously as either aquatic or terrestrial (Barbier et al. 1997). In the United States, the four general categories of wetlands, according to the Environmental Protection Agency, are marshes, swamps, bogs, and fens (EPA 2004).
The Environmental Prortection Agency defines marshes as "wetlands frequently or continually inundated with water, characterized by emergent soft-stemmed vegetation adapted to saturated soil conditions" (EPA 2006).
The National Wetlands Research Center of the U.S. Geological Survey defines marshes as "a wetland dominated by grasses" (NWRC 2007).
The Natural Resources Conservation Service of the United States Department of Agriculture defines wetlands as "periodically wet or continually flooded areas with the surface not deeply submerged; covered dominantly with sedges, cattails, rushes, or other hydrophytic plants." (NRCS 2007).
The National Safety Council defines swamps as "a type of wetland that does not accumulate appreciable peat deposits and is dominated by herbaceous vegetation (NSC 2005).
However, although in North America marshes and swamps are usually differentiated based on swamps including a large amount of woody vegetation and marshes mainly soft-stemmed vegetation (EPA 2004; NSC 2005; NRCS 2007), this definition is not universal. Marshes are further distinguished from swamps by having water that is not as deep.
Types
There are many types of marshes. Marshes may be freshwater, brackish water, or saltwater, and may be tidal or non-tidal (NSC 2005; EPA 2006).
NWRC 2007
BRACKISH MARSH - marshes occurring where salinity ranges from 3-15 parts per thousand (ppt); dominated by Spartina patens (wiregrass)
FRESHWATER MARSH - grassy wetlands that occur along rivers and lakes; dominated by grasses, reeds, rushes, and sedges
INTERMEDIATE MARSH - a marsh occurring where the salinity is about 3 parts per thousand (ppt) - a transitional area between fresh and brackish marshes; common plants are bull tongue, roseau cane, and wiregrass
SALTWATER MARSH - saltwater (15-18 parts per thousand or greater) wetlands occurring along the coast; dominated by saltwater grasses such as Spartina alterniflora (oyster grass)
- A fresh-water marsh's main feature is its openness, with only low-growing or "emergent" plants. It may feature grasses, rushes, reeds, typhas, sedges, and other herbaceous plants (possibly with low-growing woody plants) in a context of shallow water. It is an open form of fen.
- A coastal salt marsh may be associated with estuaries and along waterways between coastal barrier islands and the inner coast. The plants may extend from reed in mildly brackish water to salicornia on otherwise bare marine mud. It may be converted to human use as pasture (salting) or for salt production (saltern).
Coastal marshes may be associated with estuaries and along waterways between coastal barrier islands and the inner coast. The estuarine marsh, or tidal marsh, is often based on soils consisting of sandy bottoms or bay muds. An example is the Tantramar Marsh of eastern Canada.
A salt marsh is a type of marsh that is a transitional zone between land and salty or brackish water (e.g., sloughs, bays, estuaries). It is dominated by halophytic (salt tolerant) herbaceous plants.
We now know that salt marshes are one of the most biologically productive habitats on the planet, rivaling tropical rainforests.
salt marsh: flat, poorly drained area that is subject to period or occasional overflow by salt water, containing water that is brackish to strongly saline, and usually covered with a thick mat of grassy halophytic plants; e.g. a coastal marsh periodically flooded by the sea, or an inland marsh, (or salina) in an arid region and subject ot intermittent overflow by salty water.
A tidal marsh is a type of marsh that is found along coasts and estuaries of which the flooding characteristics are determined by the tidal movement of the adjacent estuary, sea or ocean [1]. According to the salinity of the flooding water, freshwater, brackish and saline tidal marshes are distinguished.
Marshes are generally characterized by very slow-moving waters. They are usually associated with adjacent rivers or lakes. (ocean)
Characteristics
Typically a marsh features grasses, rushes, reeds, typhas, sedges, and other herbaceous plants (possibly with low-growing woody plants) in a context of shallow water.
Below water decomposition processes often produce marsh gas, which may through self-ignition manifest as Will o' the wisps (aka. Jack-a-lanterns or spirites).
Images
Marsh in Point Pelee, Ontario, Canada
Marsh in Long Point, Ontario, Canada
See also
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ReferencesISBN links support NWE through referral fees
- Barbier, E. B., M. Mike Acreman, and D. Knowler. 1997. Economic Valuation of Wetlands: A Guide for Policy Makers and Planners. Gland, Switzerland: Ramsar Convention Bureau. ISBN 294007321X.
- Environmental Protection Agency. 2006. Marshes. U.S. Environmental Protection Agency. Retrieved November 15, 2007.
- Environmental Protection Agency. 2006b. Wetlands definitions. U.S. Environmental Protection Agency. November 15, 2007.
- Environmental Protection Agency. 2004. Wetlands overview. U.S. Environmental Protection Agency EPA 843-F-04-011a (December 2004). Retrieved November 15, 2007.
- Natural Resources Conservation Service (NRCS), United States Department of Agriculture. 2007. National Soil Survey Handbook: Glossary Of landform and geologic terms (Part 629). NRCS USDA. Retrieved November 15, 2007.
- National Safety Council (NSC). 2005. Marsh. Environmental Health Center, National Safety Council. Retrieved November 15, 2007.
- National Wetlands Research Center (NWRC), United States Geological Survey. 2007. Marsh. NWRC USGS. Retrieved November 15, 2007.
External links
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