A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of roles in the environment, principally water purification, flood control, carbon sink and shoreline stability. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Wetlands occur naturally on every continent except Antarctica, the largest including the Amazon River basin, the West Siberian Plain, and the Pantanal in South America. The water found in wetlands can be freshwater, brackish, or saltwater. The main wetland types include swamps, marshes, bogs, and fens; and sub-types include mangrove, carr, pocosin, and varzea.
The UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth. International conservation efforts are being used in conjunction with the development of rapid assessment tools to inform people about wetland issues.
Constructed wetlands can be used to treat municipal and industrial wastewater as well as stormwater runoff and they also play a role in water-sensitive urban design.
The substrate is usually organic in nature and may contain peat in varying amounts or be composed entirely of muck. The swamp substrate is typically nutrient-rich and neutral to alkaline but can be acidic and nutrient-poor.
Coniferous swamps vary in composition, with different species of conifer dominating, and varying amounts of deciduous hardwoods growing within the swamp. A wide diversity of plants is represented within the swamps, with certain species dominating in a variety of microhabitats dependent on factors such as available sunlight (as in cases of trees downed by wind or disease), soil Ph, standing groundwater, and differences of elevation within the swamp such as tussocks and nurse logs.
The different types of coniferous swamps are referred to according to their dominant trees. Rich conifer swamp is dominated by Northern white-cedar and typically occurs south of the climatic tension zone throughout the Midwest and northeastern United States and adjacent areas in Canada. North of the climatic tension zone, tamarack (Larix laricina) is the dominant species of conifer in minerotrophic wetlands classified as rich tamarack swamp. A roughly equal mix of hardwood trees and conifers is known as a hardwood-conifer swamp. (Full article...)
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