Wetlands definition

Swamps are forested, freshwater wetlands on submerged soils in which little peat accumulates. This is the US definition elsewhere the term also includes non-forested wetlands with reeds. Swamps tend to form in warmer climates. 

The first boreal ecosystem we consider is that most analogous to water, namely, the wetland. During summer, P averaged 0.8 mm day less than E for wetlands (Table 3). However, by definition, this comparison is incomplete for fens because water supply to this system exceeds rainfall by virtue of ground-water intrusion, although this is often difficult to quantify with certainty. In Tlible 3, the Saskatchewan, Zotino, and Schefferville sites were fens but it... 

Definition Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. For purposes of this classification, wetlands must have one or more of the following three attributes (i) at least periodically, the land supports predominately hydrophytes, (ii) the substrate is predominately undrained hydric soil, and (iii) the substrate is nonsoil and is saturated with water or covered by shallow water at some time during the growing season of each year. Source Cowardin et al. (1979). U.S. Department of Interior—Fish and Wildlife Service. This definition places emphasis on all three major attributes of wetlands, and is difficult to apply as it requires a comprehensive study of the site. The boundaries identified by this criteria are much more reliable than the EPA definition. 

The Committee on Wetlands Characterization, Water Science and Technology Board, National Academy of Sciences, developed a reference definition for wetland that stands outside the interests of any private or public agency (Lewis, 1995). A wetland is an ecosystem that depends on constant or recurrent, shallow inundation or saturation at or near the surface of the substrate. The minimum essential characteristics of a wetland are recurrent, sustained inundation or saturation at or near the surface and the presence of physical, chemical, and biological features reflective of recurrent, sustained inundation or saturation. Common diagnostic features of wetlands are hydric soils and hydrophytic vegetation. These features will be present except where specific physicochemical, biotic, or anthropogenic factors have removed them or prevented their development. ... 

Wetlands, as defined by various groups, are limited to areas in which there are emergent plants. At present this definition is the most commonly accepted, although there is considerable disagreement on the boundaries of developing wetlands from upland areas. 

In the context of soils and biogeochemistry, we provide a much broader definition of wetlands Wetlands consist of a biologically active soil or sediment in which the content of water in or the overlying floodwater is great enough to inhibit oxygen diffusion into the soil/sediment and stimulate... 

A narrower scientific definition (and the most commonly accepted one) would limit wetlands to areas in which there are plants. This type of wetland is usually much higher in soil organic matter than those without emergent plants. This is due to the high production of plant biomass and the slow rate of organic matter decomposition, because of the limited supply of oxygen in the wet soil. 

The hydroperiod of wetlands is dependent on flow, depth, frequency, duration (the amount of time wetlands are in standing water), seasonality, and frequency of flooding (average number of times wetlands are flooded or saturated). Thus, the hydroperiod of a wetland includes all aspects of water budget (rainfall, evapotranspiration, and subsurface and surface flow) irrespective of the source of the water. The following qualitative definitions have been presented for wetland hydroperiods in tidal and nontidal wetlands (Cowardin et al., 1979 summarized by Mitsch and Gosselink, 2000). 

Although this definition primarily focuses on uplands, in a broader sense, it does include soils that undergo periodic or continuous flooding. Depending on scientific disciplines and ecosystems, soils saturated with water are often called flooded soils, wetland soils, waterlogged soils, and marsh soils. Soil scientists have used terms such as flooded soils, waterlogged soils, and paddy soils. Ecologists refer to these systems as wetland soils. Now, wetland soils have been defined as hydric soils. 

By definition, all wetlands have hydric soils. However, land areas with hydric soil features may not support all functions of wetlands. With a broader definition, wetland soils can be divided into the following major groups ... 

Wetlands are usually defined by hydric soils, the presence of vegetation adapted to wet conditions, and hydrology. There are several definitions of wetlands, each stressing different characteristics and wetland values. 

Discuss the various definitions of wetlands, including how they differ. 

Two sets of data are given to illustrate how different researchers have arrived at different figures this is because definitions of biome types vary. Note that wetlands were examined in Section 4.5 and croplands are discussed in Section 6.2. It must also be noted that the living components of the Earth s biomes contribute to carbon flows other than those related to the large scale biosphere - atmosphere exchanges etc. These include the provision of medicines, fibres, perfumes, foods and biomass fuels. 

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