Marsh
In geography, a marsh, or morass, is a type of wetland which is subject to frequent or continuous inundation.[1] 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. A marsh is different from a swamp, which has a greater proportion of open water surface, and is generally deeper than a marsh. In North America, the term swamp is used for wetland dominated by trees rather than grasses and low herbs.
In North America, swamps are usually regarded as wetlands dominated by trees and woody bushes rather than grasses and low herbs, while a marsh in North America is a wetland dominated by soft-stemmed vegetation, rather than woody vegetation (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 swamp is distinguished from a marsh by being a wetland with more open water surface and deeper water than a marsh.
The water of a marsh can be fresh, brackish or saline. 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. Historically, salt marshes have sometimes been treated as "wastelands", along with other wetlands. We now know that salt marshes are one of the most biologically productive habitats on the planet, rivaling tropical rainforests.
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 [2]. According to the salinity of the flooding water, freshwater, brackish and saline tidal marshes are distinguished.
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).
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.
- 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).
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).
EPA 2006. "Marshes are defined as wetlands frequently or continually inundated with water, characterized by emergent soft-stemmed vegetation adapted to saturated soil conditions."
The National Wetlands Research Center of the U.S. Geological Survey defines swamps as "" (NWRC 2007). MARSH - an environment where terrestrial and aquatic habitats overlap; a wetland dominated by grasses 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)
The Natural Resources Conservation Service of the United States Department of Agriculture defines wetlands as "" (NRCS 2007).
marsh: periodically wet or continually flooded areas with the surface not deeply submerged. Covered dominantly with sedges, cattails, rushes, or other hydrophytic plants.
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.
The National Safety Council defines swamps as "a type of wetland that does not accumulate appreciable peat deposits and is dominated by herbaceous vegetation. Marshes may be either fresh or saltwater, tidal or non-tidal." (NSC 2005).
However, although in North America swamps are usually regarded as including a large amount of woody vegetation (EPA 2004; NSC 2005; NRCS 2007), this definition is not universal.
Marshes are generally characterized by very slow-moving waters. They are usually associated with adjacent rivers or lakes. (ocean)
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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- ↑ U.S. Environmental Protection Agency: Characterization of marshes
- ↑ [1] U.S. Environmental Protection Agency: Tidal marshes
