Freshwater Wetlands - Hydro-Environmental Analysis: Freshwater Environments - page 510

FIGURE 19.1 Example of a wetland. (From the cover page of Dahl, T.E., Status and trends of wetlands in the
conterminous United States 1986 to 1997. U.S. Fish and Wildlife Service, Washington, DC, 2000.)
Some of the available deinitions by federal agencies are provided in Table 19.1. In many cases,
individual states or other organizations also have speciic deinitions, which, in some cases, are in
conlict.
19.2 WETLAND TYPES
One aspect of deining a wetland is to develop a wetlands classiication system. Conversely, the
classiication of wetlands, as discussed later, emphasizes the dificulty in arriving at a general
deinition.
There are a variety of types and classiication systems of wetlands. The wetland types or classii-
cations often depend upon the speciic purpose of that classiication, such as for research or regula-
tory purposes or to delineate wetlands from other terrestrial or aquatic systems. The characteristics
of wetlands are also a foundation for their protection and management. For example, bogs and fens
are often characterized as dificult or impossible to replace, so they may receive greater protection
than other wetland types.
19.2.1 b oGS and f enS
Bogs are found on saturated, low-nutrient, acidic, peat soils that only support low shrubs, herbs, and
a few tree species on a mat of sphagnum moss. While their productivity is low, bogs have substan-
tial peat accumulation (>40 cm) and accumulations of partially decayed vegetation. Additionally,
they have high water tables and contain acid-loving vegetation. Bogs are stagnant systems, with no