Northern Prairie Wildlife Research Center
Classification of Wetlands and Deepwater Habitats of the United States
Definition. The Class Forested Wetland is characterized by woody
vegetation that is 6 m tall or taller. All water regimes are
included except subtidal.
Description. Forested Wetlands are most common in the eastern
United States and in those sections of the West where moisture is
relatively abundant, particularly along rivers and in the
mountains. They occur only in the Palustrine and Estuarine Systems
and normally possess an overstory of trees, an understory of young
trees or shrubs, and a herbaceous layer. Forested Wetlands in the
Estuarine System, which include the mangrove forests of Florida,
Puerto Rico, and the Virgin Islands, are known by such names as
swamps, hammocks, heads, and bottoms. These names often occur in
combination with species names or plant associations such as cedar
swamp or bottomland hardwoods.
Subclasses and Dominance Types.
Broad-leaved Deciduous. -- Dominant trees typical of Broadleaved
Deciduous Wetlands, which are represented throughout the
United States, are most common in the South and East. Common
dominants are species such as red maple, American elm (Ulmus
americana), ashes (Fraxinus pennsylvanica and F. nigra), black gum
(Nyssa sylvatica), tupelo gum (N. aquatica), swamp white oak
(Quercus bicolor), overcup oak (Q. lyrata), and basket oak (Q.
michauxii). Wetlands in this subclass generally occur on mineral
soils or highly decomposed organic soils.
Needle-leaved Deciduous. -- The southern representative of the
Needle-leaved Deciduous Subclass is bald cypress (Taxodium
distichum), which is noted for its ability to tolerate long
periods of surface inundation. Tamarack is characteristic of the
Boreal Forest Region, where it occurs as a dominant on organic
soils. Relatively few other species are included in this Subclass.
Broad-Leaved Evergreen. -- In the Southeast, Broadleaved Evergreen
Wetlands reach their greatest development. Red bay (Persea
borbonia), loblolly bay (Gordonia lasianthus), and sweet bay
(Magnolia virginiana) are prevalent, especially on organic soils.
This Subclass also includes red mangrove, black mangrove
(Avicennia germinans), and white mangrove (Languncularia
racemosa), which are adapted to varying levels of salinity.
Needle-leaved Evergreen. -- Black spruce, growing on organic
soils, represents a major dominant of the Needle-leaved Evergreen
Subclass in the North. Though black spruce is common on nutrient-poor
soils, Northern white cedar (Thuja occidentalis) dominates
northern wetlands on more nutrient-rich sites. Along the Atlantic
Coast, Atlantic white cedar (Chamaecyparis thyoides) is one of the
most common dominants on organic soils. Pond pine is a common
needle-leaved evergreen found in the Southeast in association with
dense stands of broad-leaved evergreen and deciduous shrubs.
Dead. -- Dead Forested Wetlands are dominated by dead woody
vegetation taller than 6 m (20 feet). Like Dead Scrub-Shrub
Wetlands, they are most common in, or around the edges of, man-made
impoundments and beaver ponds. The same factors that produce
Dead Scrub-Shrub Wetlands produce Dead Forested Wetlands.
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