PART III: CHARACTERISTICS AND INDICATORS OF HYDROPHYTIC 

 VEGETATION, HYDRIC SOILS, AND WETLAND HYDROLOGY 



Hydrophytic Vegetation 



Definition 



29. Hydrophytic vegetation. Hydrophytic vegetation is defined herein 

 as the sum total of macrophytic plant life that occurs in areas where the 

 frequency and duration of inundation or soil saturation produce permanently or 

 periodically saturated soils of sufficient duration to exert a controlling 

 influence on the plant species present. The vegetation occurring in a wetland 

 may consist of more than one plant community (species association). The plant 

 community concept is followed throughout the manual. Emphasis is placed on 

 the assemblage of plant species that exert a controlling influence on the 

 character of the plant community, rather than on indicator species. Thus, the 

 presence of scattered individuals of an upland plant species in a community 

 dominated by hydrophytic species is not a sufficient basis for concluding that 

 the area is an upland community. Likewise, the presence of a few individuals 

 of a hydrophytic species in a community dominated by upland species is not a 

 sufficient basis for concluding that the area has hydrophytic vegetation. 

 CAUTION: In determining whether an area is "vegetated" for the purpose of 

 Section 404 jurisdiction, users must consider the density of vegetation at the 

 site being evaluated. While it is not possible to develop a numerical method 

 to determine how many plants or how much biomass is needed to establish an 

 area as being vegetated or unvegetated, it is intended that the predominant 

 condition of the site be used to make that characterization. This concept 

 applies to areas grading from wetland to upland, and from wetland to other 

 waters. This limitation would not necessarily apply to areas which have been 

 disturbed by man or recent natural events. 



30. Prevalence of vegetation. The definition of wetlands (para- 

 graph 26a) includes the phrase "prevalence of vegetation." Prevalence, as 

 applied to vegetation, is an imprecise, seldom-used ecological term. As used 

 in the wetlands definition, prevalence refers to the plant community or com- 

 munities that occur in an area at some point in time. Prevalent vegetation is 

 characterized by the dominant species comprising the plant community or com- 

 munities. Dominant plant species are those that contribute more to the char- 

 acter of a plant community than other species present, as estimated or 



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