measured in terms of some ecological parameter or parameters. The two most 

 commonly used estimates of dominance are basal area (trees) and percent areal 

 cover (herbs). Hydrophytic vegetation is prevalent in an area when the domi- 

 nant species comprising the plant community or communities are typically 

 adapted for life in saturated soil conditions. 



31. Typically adapted. The term "typically adapted" refers to a spe- 

 cies being normally or commonly suited to a given set of environmental condi- 

 tions, due to some morphological, physiological, or reproductive adaptation 

 (Appendix C, Section 3). As used in the CE wetlands definition, the governing 

 environmental conditions for hydrophytic vegetation are saturated soils re- 

 sulting from periodic inundation or saturation by surface or ground water. 

 These periodic events must occur for sufficient duration to result in 

 anaerobic soil conditions. When the dominant species in a plant community are 

 typically adapted for life in anaerobic soil conditions, hydrophytic vegeta- 

 tion is present. Species listed in Appendix C, Section 1 or 2 , that have an 

 indicator status of OBL, FACW, or FAC* (Table 1) are considered to be 

 typically adapted for life in anaerobic soil conditions (see paragraph 35a). 

 Influencing factors 



32. Many factors (e.g. light, temperature, soil texture and permeabil- 

 ity, man-induced disturbance, etc.) influence the character of hydrophytic 

 vegetation. However, hydrologic factors exert an overriding influence on spe- 

 cies that can occur in wetlands. Plants lacking morphological, physiological, 

 and/or reproductive adaptations cannot grow, effectively compete, reproduce, 

 and/or persist in areas that are subject to prolonged inundation or saturated 

 soil conditions. 



Geographic diversity 



33. Many hydrophytic vegetation types occur in the United States due to 

 the diversity of interactions among various factors that influence the distri- 

 bution of hydrophytic species. General climate and flora contribute greatly 

 to regional variations in hydrophytic vegetation. Consequently, the same as- 

 sociations of hydrophytic species occurring in the southeastern United States 

 are not found in the Pacific Northwest. In addition, local environmental con- 

 ditions (e.g. local climate, hydrologic regimes, soil series, salinity, etc.) 



* Species having a FAC- indicator status are not considered to be typically 

 adapted for life in anaerobic soil conditions. 



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