2 2 



as reed {Phragmites communis), manna grasses (G/v- 

 ceria spp.), slough grass (Beckmannia syzigachne), and 

 whitetop [Scolochloa festucacea). There is also a 

 variety of broad-leaved persistent emergents such as 

 purple loosestrife {Lythrum salicaria), dock (Rumex 

 mexicanus), waterwillow {Decodon vertieillatus), and 

 many species of smartweeds {Polygonum). 



Nonpersistent.— Wetlands in this subclass are 

 dominated by plants which fall to the surface of the 

 substrate or below the surface of the water at the end 

 of the growing season so that, at certain seasons of the 

 year, there is no obvious sign of emergent vegetation. 

 For example, wild rice (Zizania aquatica) does not 

 become apparent in the North Central States until 

 midsummer and fall, when it may form dense emergent 

 stands. Nonpersistent emergents also include species 

 such as arrow arum {Peltandra virginica), pickerelweed 

 (Pontederia cordata), and arrowheads (Sagittaria spp.). 

 Movement of ice in Estuarine, Riverine, and Lacus- 

 trine systems often removes all traces of emergent 

 vegetation during the winter. Where this occurs, the 

 area should be classified as Nonpersistent Emergent 

 Wetland. 



Scrub-Shrub Wetland 



Definition. The class Scrub-Shrub Wetland includes 

 areas dominated by woody vegetation less than 6 m 

 (20 feet) tall. The species include true shrubs, young 

 trees, and trees or shrubs that are small or stunted 

 because of environmental conditions. All water 

 regimes except subtidal are included. 



Description. Scrub-Shrub Wetlands may represent 

 a successional stage leading to Forested Wetland, or 

 they may be relatively stable communities. They occur 

 only in the Estuarine and Palustrine systems, but are 

 one of the most widespread classes in the United 

 States (Shaw and Fredine 1956). Scrub-Shrub Wet- 

 lands are known by many names, such as shrub swamp 

 (Shaw and Fredine 1956), shrub carr (Curtis 1959), bog 

 (Heinselman 1970), and pocosin (Kologiski 1977). For 

 practical reasons we have also included forests com- 

 posed of young trees less than 6 m tall. 



Subclasses and Dominance Types. 

 Broad-leaved Deciduous.— In Estuarine System 

 wetlands the predominant deciduous and broad-leaved 

 trees or shrubs are plants such as sea-myrtle (Bacchar- 

 is halimifolia) and marsh elder (Iva frutescens). In the 

 Palustrine System typical dominance types are alders 

 (Alnus spp.), willows (Salix spp.), buttonbush (Ceph- 

 alanthus occidentalis), red osier dogwood (Cornus 

 stolonifera), honeycup (Zenobia pulverulenta), spirea 

 {Spiraea douglasii), bog birch (Betula pumila), and 

 young trees of species such as red maple (Acer rubrum) 

 or black spruce (Picea mariana). 



Needle-leaved Deciduous. —This subclass, consist- 

 ing of wetlands where trees or shrubs are pre- 

 dominantly deciduous and needle-leaved, is repre- 



sented by young or stunted trees such as tamarack or 

 bald cypress (Taxodium distichum). 



Broad-leaved Evergreen. — In the Estuarine 

 System, vast wetland acreages are dominated by 

 mangroves (Rhizophora mangle. Languncularia race- 

 mosa, Conocarpus erectus, and Avicennia germinans) 

 that are less than 6 m tall. In the Palustrine System, 

 the broad-leaved evergreen species are typically found 

 on organic soils. Northern representatives are labra- 

 dor tea {Ledum groenlandicum), bog rosemary {An- 

 dromeda glaucophylla), bog laurel {Kalmia polifolia), 

 and the semi-evergreen leatherleaf {Chamaedaphne 

 calyculata). In the south, fetterbush (Lyonia lucida), 

 coastal sweetbells (Leucothoe axillaris), inkberry {Ilex 

 glabra), and the semi-evergreen black ti-ti (Cyrilla 

 racemiflora) are characteristic broad-leaved evergreen 

 species. 



Needle-leaved Evergreen.— The dominant species 

 in Needle-leaved Evergreen wetlands are young or 

 stunted trees such as black spruce or pond pine (Pinus 

 serotina). 



Dead— Head woody plants less than 6m tall 

 dominate dead scrub-shrub wetlands. These wetlands 

 are usually produced by a prolonged rise in the water 

 table resulting from impoundment of water by land- 

 slides, man, or beavers. Such wetlands may also result 

 from various other factors such as fire, salt spray, 

 insect infestation, air pollution, and herbicides. 



Forested Wetland 



Definition. The class Forested Wetland is charac- 

 terized 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, par- 

 ticularly 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 Broad-leaved Deciduous wetlands, which are repre- 

 sented 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). 



