10 



Table 2. Salinity Modifiers used in this classification system. 



Coastal Modifiers" 



Inland Modifiers' 1 



Salinity (parts per thousand) 



>40 



30.0-40 



0.5-30 



18.0-30 



5.0-18 



0.5-5 



<0.5 



"Coastal Modifiers are used in the Marine and Estuarine Systems. 



Tnland Modifiers are used in the Riverine, Lacustrine, and Palustrine Systems. 



c The term Brackish should not be used for inland wetlands or deepwater habitats. 



Approximate 



specific conductance 



Q/Mhos at 25°C) 



>60,000 



45,000-60,000 



800-45,000 



30,000-45,000 



8,000-30,000 



800- 8,000 



<800 



system to a depth of 2 m (6.6 feet) below low water or 

 to the maximum extent of nonpersistent emergents, if 

 these grow at depths greater than 2 m. 



Classes. Rock Bottom, Unconsolidated Bottom, Aquatic 

 Bed, Rocky Shore, Unconsolidated Shore, and Emergent 

 Wetland (nonpersistent). 



Palustrine System 



Definition. The Palustrine System (Fig. 6) includes all 

 nontidal wetlands dominated by trees, shrubs, persistent 

 emergents, emergent mosses or lichens, and all such wet- 

 lands that occur in tidal areas where salinity due to ocean- 

 derived salts is below 0.5°/oo. It also includes wetlands 

 lacking such vegetation, but with all of the following four 

 characteristics: (1) area less than 8 ha (20 acres); (2) ac- 

 tive wave-formed or bedrock shoreline features lacking; 

 (3) water depth in the deepest part of basin less than 2 m 

 at low water; and (4) salinity due to ocean-derived salts 

 less than 0.5%>o. 



Limits. The Palustrine System is bounded by upland or 

 by any of the other four Systems. 



Description. The Palustrine System was developed to 

 group the vegetated wetlands traditionally called by such 

 names as marsh, swamp, bog, fen, and prairie, which are 

 found throughout the United States. It also includes the 

 small, shallow, permanent or intermittent water bodies 

 often called ponds. Palustrine wetlands may be situated 

 shoreward of lakes, river channels, or estuaries; on river 

 floodplains; in isolated catchments; or on slopes. They may 

 also occur as islands in lakes or rivers. The erosive forces 

 of wind and water are of minor importance except dur- 

 ing severe floods. 



The emergent vegetation adjacent to rivers and lakes 

 is often referred to as "the shore zone" or the "zone of 

 emergent vegetation" (Reid and Wood 1976), and is gen- 

 erally considered separately from the river or lake. As an 

 example, Hynes (1970:85) wrote in reference to riverine 

 habitats, "We will not here consider the long list of emer- 

 gent plants which may occur along the banks out of the 



current, as they do not belong, strictly speaking, to the 

 running water habitat." There are often great similarities 

 between wetlands lying adjacent to lakes or rivers and 

 isolated wetlands of the same class in basins without open 

 water. 



Subsystems. None. 



Classes. Rock Bottom, Unconsolidated Bottom, Aquatic 

 Bed, Unconsolidated Shore, Moss-Lichen Wetland, Emer- 

 gent Wetland, Scrub-Shrub Wetland, and Forested 

 Wetland. 



Classes, Subclasses, and Dominance Types 



The CLASS is the highest taxonomic unit below the Sub- 

 system level. It describes the general appearance of the 

 habitat in terms of either the dominant life form of the 

 vegetation or the physiography and composition of the 

 substrate— features that can be recognized without the aid 

 of detailed environmental measurements. Vegetation is 

 used at two different levels in the classification. The life 

 forms— trees, shrubs, emergents, emergent mosses, and 

 lichens— are used to define Classes because they are 

 relatively easy to distinguish, do not change distribution 

 rapidly, and have traditionally been used as criteria for 

 classification of wetlands. 4 Other forms of vegetation, such 

 as submerged or floating-leaved rooted vascular plants, 

 free-floating vascular plants, submergent mosses, and 

 algae, though frequently more difficult to detect, are used 



4 Our initial attempts to use familiar terms such as marsh, swamp, 

 bog, and meadow at the Class level were unsuccessful primarily 

 because of wide discrepancies in the use of these terms in various 

 regions of the United States. In an effort to resolve that difficulty, 

 we based the Classes on the fundamental components (life form, 

 water regime, substrate type, water chemistry) that give rise to 

 such terms. We believe that this approach will greatly reduce the 

 misunderstandings and confusion that result from the use of the 

 familiar terms. 



