U 



UPLAND PALUSTRINE UPLAND 



PALUSTRINE 



UPLAND 



PALUSTRINE 



UPLAND 



Seepage Zone 



a TEMPORARILY FLOODED 



b SEASONALLY FLOODED 



c SEMIPERMANENTLY FLOODED 



d INTERMITTENTLY EXPOSED 



e PERMANENTLY FLOODED 



f SATURATED 



■HIGH WATER 

 VERAGE WATER 

 LOW WATER 



Fig. 6. Distinguishing features and examples of habitats in the Palustrine System. 



assigned to the class Scrub-Shrub. When trees and 

 shrubs cover less than 30% of the area but the total 

 cover of vegetation (except pioneer species) is 30% or 

 greater, the wetland is assigned to the appropriate 

 class for the predominant life form below the shrub 

 layer. Finer differences in life forms are recognized at 

 the subclass level. For example, Forested Wetland is 

 divided into the subclasses Broad-leaved Deciduous, 

 Needle-leaved Deciduous, Broad-leaved Evergreen, 

 Needle-leaved Evergreen, and Dead. Subclasses are 

 named on the basis of the predominant life form. 



If vegetation covers less than 30% of the substrate, 

 the physiography and composition of the substrate are 

 the principal characteristics used to distinguish 

 classes. The nature of the substrate reflects regional 

 and local variations in geology and the influence of 

 wind, waves, and currents on erosion and deposition of 

 substrate materials. Bottoms, Shores, and Stream- 

 beds are separated on the basis of duration of inun- 

 dation. In the Riverine, Lacustrine, and Palustrine 

 systems, Bottoms are submerged all or most of the 

 time, whereas Streambeds and Shores are exposed all 

 or most of the time. In the Marine and Estuarine 

 systems, Bottoms are subtidal, whereas Streambeds 



and Shores are intertidal. Bottoms, Shores, and 

 Streambeds are further divided at the class level on 

 the basis of the important characteristic of rock versus 

 unconsolidated substrate. Subclasses are based on 

 finer distinctions in substrate material unless, as with 

 Streambeds and Shores, the substrate is covered by, 

 or shaded by, an aerial coverage of pioneering vascular 

 plants (often nonhydrophytes) of 30% or more; the 

 subclass is then simply vegetated. Further detail as to 

 the type of vegetation must be obtained at the level of 

 dominance type. Reefs are a unique class in which the 

 substrate itself is composed primarily of living and 

 dead animals. Subclasses of Reefs are designated on 

 the basis of the type of organism that formed the reef. 



The DOMINANCE TYPE is the taxonomic category 

 subordinate to subclass. Dominance types are deter- 

 mined on the basis of dominant plant species (e.g., 

 Jeglum et al. 1974), dominant sedentary or sessile 

 animal species (e.g., Thorson 1957), or dominant plant 

 and animal species (e.g., Stephenson and Stephenson 

 1972). A dominant plant species has traditionally 

 meant one that has control over the community 

 (Weaver and Clements 1938:91), and this plant is also 

 usually the predominant species (Cain and Castro 



