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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 Palus- 

 trine 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 Estu- 

 arine 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 

 Broad-leaved 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 (Frax- 

 inus 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 representa- 

 tive 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, Broad- 

 leaved Evergreen Wetlands reach their greatest develop- 

 ment. 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 ger- 

 minans), 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 South- 

 east 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. 



Modifiers 



To fully describe wetlands and deepwater habitats, one 

 must apply certain Modifiers at the Class level and at lower 

 levels in the classification hierarchy. The Modifiers 

 described below were adapted from existing classifications 

 or were developed specifically for this system. 



Water Regime Modifiers 



Precise description of hydrologic characteristics requires 

 detailed knowledge of the duration and timing of surface 

 inundation, both yearly and long-term, as well as an under- 

 standing of groundwater fluctuations. Because such in- 

 formation is seldom available, the water regimes that, in 

 part, determine characteristic wetland and deepwater 

 plant and animal communities are described here in only 

 general terms. Water regimes are grouped under two ma- 

 jor headings, Tidal and Nontidal. 



Tidal Water Regime Modifiers are used for wetlands and 

 deepwater habitats in the Estuarine and Marine Systems 

 and Nontidal Modifiers are used for all nontidal parts of 

 the Palustrine, Lacustrine, and Riverine Systems. The 

 Tidal Subsystem of the Riverine System and tidally in- 

 fluenced parts of the Palustrine and Lacustrine Systems 

 require careful selection of Water Regime Modifiers. We 

 designate subtidal and irregularly exposed wetlands and 

 deepwater habitats in the Palustrine, Riverine, and Lacus- 

 trine Systems as permanently flooded-tidal rather than 

 subtidal, and Palustrine, Riverine, and Lacustrine wet- 

 lands regularly flooded by the tide as regularly flooded. 

 If Palustrine, Riverine, and Lacustrine wetlands are on- 

 ly irregularly flooded by tides, we designate them by the 

 appropriate nontidal Water Regime Modifier with the 

 word tidal added, as in seasonally flooded-tidal. 



Tidal 



The water regimes are largely determined by oceanic 

 tides. 



Subtidal. The substrate is permanently flooded with 

 tidal water. 



Irregularly Exposed. The land surface is exposed by 

 tides less often than daily. 



Regularly Flooded. Tidal water alternately floods and 

 exposes the land surface at least once daily. 



Irregularly Flooded. Tidal water floods the land surface 

 less often than daily. 



The periodicity and amplitude of tides vary in different 

 parts of the United States, mainly because of differences 

 in latitude and geomorphology. On the Atlantic Coast, two 

 nearly equal high tides are the rule (semidiurnal). On the 

 Gulf Coast, there is frequently only one high tide and one 

 low tide each day (diurnal); and on the Pacific Coast there 



