21 



than stones is predominantly organic soils of formerly 

 vegetated wetlands. In the Marine and Estuarine 

 systems, Organic Shores are often dominated by 

 microinvertebrates such as foraminifera, and by Nas- 

 sarius, Littorina, Uca, Modiolus, Mya, Nereis, and the 

 false angel wing Petricola pholadiformis. In the Lacus- 

 trine, Palustrine, and Riverine systems, examples of 

 dominance types are Canthocamptus, Bryocamptus, 

 Chironomus, and the backswimmer Notonecta. 



Vegetated. — Some nontidal shores are exposed for 

 a sufficient period to be colonized by herbaceous an- 

 nuals or seedling herbaceous perennials (pioneer 

 plants). This vegetation, unlike that of Emergent 

 Wetlands, is usually killed by rising water levels and 

 may be gone before the beginning of the next growing 

 season. Many of the pioneer species are not hydro- 

 phytes but are weedy mesophytes that cannot tolerate 

 wet soil or flooding. Examples of dominance types in 

 the Palustrine, Riverine, and Lacustrine systems are 

 cocklebur {Xanthium strummarium) and barnyard 

 grass (Echinochloa crusgalli). 



Dominance types for unconsolidated shores in the 

 Marine and Estuarine systems were taken primarily 

 from Smith (1964), Morris (1966), Abott (1968), 

 Ricketts and Calvin (1968), and Gosner (1971). Domi- 

 nance types for unconsolidated shores in the Lacus- 

 trine, Riverine, and Palustrine systems were taken pri- 

 marily from Stehr and Branson (1938), Kenk (1949), 

 Ward and Whipple (1959), Cummins et al. (1964), 

 Johnson (1970), Ingram (1971), Clarke (1973), and Hart 

 and Fuller (1974). 



Moss-Lichen Wetland 



Definition. The Moss-Lichen Wetland class includes 

 areas where mosses or lichens cover substrates other 

 than rock and where emergents, shrubs, or trees make 

 up less than 30% of the areal cover. The only water 

 regime is saturated. 



Description. Mosses and lichens are important com- 

 ponents of the flora in many wetlands, especially in the 

 north, but these plants usually form a ground cover 

 under a dominant layer of trees, shrubs, or emergents. 

 In some instances higher plants are uncommon and 

 mosses or lichens dominate the flora. Such 

 Moss-Lichen wetlands are not common, even in the 

 northern United States where they occur most fre- 

 quently. 



Subclasses and Dominance Types. 

 Moss. —Moss wetlands are most abundant in the 

 far north. Areas covered with peat mosses {Sphagnum 

 spp.) are usually called bogs (Golet and Larson 1974; 

 Jeglum et al. 1974; Zoltai et al. 1975), whether Sphag- 

 num or higher plants are dominant. In Alaska, 

 Drepanocladus and the liverwort Chiloscyphus fragilis 

 may dominate shallow pools with impermanent water; 

 peat moss and other mosses (Campylium stellatum, 

 Aulacomnium palustre, and Oncophorus wahlenbergii) 



are typical of wet soil in this region (Britton 1957; 

 Drury 1962). 



Lichen.— Lichen wetlands are also a northern sub- 

 class. Reindeer moss {Cladonia rangiferina) forms the 

 most important dominance type. Pollett and Bridge- 

 water (1973) described areas with mosses and lichens 

 as bogs or fens, the distinction being based on the 

 availability of nutrients and the particular plant 

 species present. The presence of Lichen Wetlands has 

 been noted in the Hudson Bay Lowlands (Sjors 1959) 

 and in Ontario (Jeglum et al. 1974). 



Emergent Wetland 



Definition. The Emergent Wetland class is charac- 

 terized by erect, rooted, herbaceous hydrophytes, 

 excluding mosses and lichens. This vegetation is 

 present for most of the growing season in most years. 

 These wetlands are usually dominated by perennial 

 plants. All water regimes are included except subtidal 

 and irregularly exposed. 



Description. In areas with relatively stable climatic 

 conditions, Emergent Wetlands maintain the same 

 appearance year after year. In other areas, such as the 

 prairies of the central United States, violent climatic 

 fluctuations cause them to revert to an open water 

 phase in some years (Stewart and Kantrud 1972). 

 Emergent Wetlands are found throughout the United 

 States and occur in all systems except the Marine. 

 Emergent Wetlands are known by many names, in- 

 cluding marsh, meadow, fen, prairie pothole, and 

 slough. Areas that are dominated by pioneer plants 

 that become established during periods of low water 

 are not Emergent Wetlands and should be classified as 

 Vegetated Unconsolidated Shores or Vegetated 

 Streambeds. 



Subclasses and Dominance Types. 

 Persistent.— Persistent Emergent Wetlands are 

 dominated by species that normally remain standing 

 at least until the beginning of the next growing season. 

 This subclass is found only in the Estuarine and Palus- 

 trine systems. 



Persistent Emergent Wetlands dominated by salt- 

 marsh cordgrass (Spartina alterniflora), saltmeadow 

 cordgrass (S. patens), big cordgrass (S. cynosuroides), 

 needlerush IJuncus roemerianus), narrow-leaved cat- 

 tail {Typha angustifolia), and southern wild rice (Zi- 

 zaniopsis miliacea) are major components of the 

 Estuarine Systems of the Atlantic and Gulf coasts of 

 the United States. On the Pacific Coast, common 

 pickleweed {Salicornia virginica), sea blite {Suaeda cali- 

 fornica), arrow grass (Triglochin maritima), and Cali- 

 fornia cordgrass (Spartina foliosa) are common domi- 

 nants. 



Palustrine Persistent Emergent Wetlands contain a 

 vast array of grasslike plants such as cattails (Typha 

 spp.), bulrushes (Scirpus spp.), saw grass (Cladium 

 jamaicense), sedges (Carex spp.); and true grasses such 



