Wetland Natural Communities

from the 2015 NCWAP:

Wetlands perform many ecosystem services, including flood protection and pollution control, and they provide essential breeding, rearing, and foraging sites for numerous fish and wildlife species. Wetlands are defined by hydrology (wetness), plant community com- position, and soil characteristics (FGDC 2013; Cowardin et al. 1979). From a landscape perspective, they function as transitional lands between terrestrial and aquatic systems where the water table is at or near the land surface or where the land is covered by shallow water (FGDC 2013; Cowardin et al. 1979).

Wetlands are regulated under the Clean Water Act, Sections 404 and 401, and the USACE has regulatory authority over impacts to sites that have been delineated as jurisdictional resources (USACE 1987). Wetlands that fall under regulatory authority have one or more of three attributes: they support predominantly hydrophytic vegetation at least periodically; the substrate is predominantly undrained hydric soil; or the substrate is nonsoil and is saturated with water or covered by shallow water at some time during the growing season each year (FGDC 2013). Hydrophytic vegetation are plants that grow in water or on a substrate (e.g., soil) that is at least periodically deficient in oxygen as a result of excessive water con- tent (Cowardin et al. 1979). Hydric soils are wet long enough to periodically produce anaerobic conditions, thereby influencing the growth and type of plants that occur (Cowardin et al. 1979).

There are several methods for characterizing wetlands that are based on dominant vege- tation communities, dominant soil characteristics, or dominant hydrologic factors. One method defines them based on the relationship between hydrology, geomorphology, and function (Brinson 1993). The approach places emphasis on the importance of abiotic features such as the chemical characteristics of water, habitat maintenance, and water storage and transport. In this document wetland communities are defined based on descriptions by Schafale and Weakley (1990) and Schafale (2012), which use dominant vegetation characteris- tics and hydrology as a basis for their descriptions.

Wetland community descriptions are provided in alphabetical order in Sections 4.3.1 through 4.3.11. Floodplain communities have been included in this Section as a wetland community type; however, depending on the location of some floodplains the landscape may also be interspersed with upland communities. Mountain and Piedmont bogs are among the rarest natural communities in the Southern Appalachians and in North Carolina. Unlike northern bogs of glacial origin, Southern Appalachian bogs form in poorly drained depressions or on gentle slopes, generally in relatively flat valley bottoms which are not subject to flooding. They may vary from being permanently wet to intermittently dry and are generally fed by seepage. They are underlain by wet organic or mucky mineral soils, which are very acidic.

The factors responsible for creating and maintaining bog communities are not well known. Grazing has been nearly universal in bogs, and few examples exist in pristine condition. Most are experiencing invasion of shrubs or trees at the expense of the herbaceous zones. This tendency toward rapid succession suggests that some form of periodic or chronic natural disturbance, now disrupted, may have kept the bogs open. Potential past disturbances include flooding by Beavers, grazing by herds of large mammals, fires, and clearing by Native Americans.

There are three community types within this ecosystem: Southern Appalachian bog, Southern Appalachian fen, and swamp forest–bog complex:

• The Southern Appalachian bog and Southern Appalachian fen types have a mosaic or zoned pattern of shrub thickets and herb-dominated areas, mostly underlain by sphag- num mats. Trees may be scattered throughout or may dominate on the edges. The shrub and herb layers of the bog, while not highly diverse, are uniquely adapted to the acidic, nutrient-poor environment of the bog and may include numerous rare species. Fens occur on high pH (basic) soils, but otherwise have the same vegetative zones as bogs; only one Southern Appalachian fen is known in North Carolina (in Ashe County).

• Swamp forest-bog complex types occur along streams and are dominated by trees, but may have boggy herbs and sphagnum moss in canopy openings.

The 2005 WAP described bogs and associated wetlands (mountain bogs) as a priority habitat in the Southern Blue Ridge Mountains ecoregion (see Chapter 5) (NCWRC 2005).