Definition: In Forested Wetlands, trees are the dominant life form—i.e., the tallest life form with at least 30 percent areal coverage. Trees are defined as woody plants at least 6 m (20 ft) in height. All Water Regimes except Subtidal and Regularly Flooded-Tidal Fresh are included. Not all Water Regimes apply to all subclasses.


Description: Forested Wetlands are most common in the eastern U.S. 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 an 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. Such common names are often applied, in combination with species names or plant association names, in Palustrine forests as well (e.g., cedar swamp, bottomland hardwoods). 


Subclasses and Dominance Types: 


  • Broad-leaved Deciduous -  In this Subclass, broad-leaved deciduous species have the greatest areal coverage in the tree layer. Broad-leaved Deciduous Forested Wetlands, which are represented throughout the United States, are most common in the South and East. Common Dominance Types include 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 swamp chestnut oak (Q. michauxii). Wetlands in this Subclass generally occur on mineral soils or highly decomposed organic soils. 


  • Needle-leaved Deciduous -  In this Subclass, needle-leaved deciduous species have the greatest areal coverage in the tree layer. The southern representative of the Needle-leaved Deciduous Subclass is bald cypress, 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 this Subclass, broad-leaved evergreen species have the greatest areal coverage in the tree layer. In the Southeast, Broad-leaved Evergreen Forested Wetlands reach their greatest development. Red bay (Persea borbonia), loblolly bay (Gordonia lasianthus), and sweet bay (Magnolia virginiana) are prevalent, especially on organic soils. Other Dominance Types include red mangrove (Rhizophora mangle), black mangrove (Avicennia germinans), and white mangrove (Languncularia racemosa), which are adapted to varying levels of salinity. 


  • Needle-leaved Evergreen -  In this Subclass, needle-leaved evergreen species have the greatest areal coverage in the tree layer. Black spruce, growing on nutrient-poor organic soils, represents a major dominant of the Needle-leaved Evergreen Subclass in the North. Eastern arborvitae (Thuja occidentalis) dominates northern wetlands on more nutrientrich 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 needleleaved evergreen found in the Southeast in association with dense stands of broad-leaved evergreen and deciduous shrubs. 


  • Dead - This Subclass includes stands of dead woody plants at least 6 m tall, regardless of their density, with less than 30 percent cover of living vegetation. If living vegetation equals or exceeds 30 percent in such stands, the Class and Subclass are based on the dominant life form of the living plants. Dead Forested Wetlands usually are produced by a prolonged rise in the water level resulting from impoundment by humans or beavers. In tidal areas, hurricanes, coastal subsidence, and sea level rise also may be responsible.

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