given plant community. These are accepted meth- 

 ods for evaluating plant communities. 



Field Indicators 



3.6. Having established the community dominants 

 for each stratum or performed a frequency analysis, 

 hydrophytic vegetation is considered present if: 



1) OBL species comprise all dominants in the 

 plant community (Note: In these cases, the area can 

 be considered wetland without detailed examination 

 of soils and hydrology, provided significant hydro- 

 logic modifications are not evident); or 



2) OBL species do not dominate each stratum, 

 but more than 50 percent of the dominants of all 

 strata are OBL, FACW, or FAC species (including 

 FACW+, FACW-, FAC+, and FAC-); or 



3) A plant community has a visually estimated 

 percent coverage of OBL and FACW species that 

 exceed the coverage of FACU and UPL species; or 



4) A frequency analysis of all species within the 

 community yields a prevalence index value of less 

 than 3.0 (where OBL = 1.0, FACW = 2.0, FAC = 

 3.0, FACU = 4.0, and UPL = 5.0); or 



5) A plant community has less than or equal to 

 50 percent of the dominant species from all strata 

 represented by OBL, FACW, and/or FAC species, 

 or a frequency analysis for all species within the 

 community yields a prevalence index value greater 

 than or equal to 3.0, and hydric soils and wetland 

 hydrology are present. (Note: In other words, if the 

 hydric soil and wetland hydrology criteria are met, 

 then the vegetation is considered hydrophytic. For 

 purposes of this manual, these situations are treated 

 as disturbed or problem area wetlands because 

 these plant communities are usually nonwetlands.) 



Other Sources of Information 



3.7. Besides learning the field indicators of hydro- 

 phytic vegetation presented above, one should also 

 become familiar with the technical literature on wet- 

 lands, especially for one's geographic region. 

 Sources of available literature include: taxonomic 

 plant manuals and field guides; scientific journals 

 dealing with botany, ecology, and wetiands in par- 



ticular; technical government reports on wetiands; 

 proceedings of wetiand workshops, conferences, 

 and symposia; and the FWS's national wetland 

 plant database, which contains habitat information 

 on about 7,000 plant species. Appendix A presents 

 examples of the first four sources of information. 

 In addition, the FWS's National Wetiands Invento- 

 ry (NWI) maps provide information on locations of 

 hydrophytic plant communities that may be studied 

 in the field to improve one's knowledge of such 

 communities in particular regions. 



Hydric Soils 



3.8. Due to their wetness during the growing sea- 

 son, hydric soils usually develop certain morpho- 

 logical properties that can be readily observed in 

 the field. Prolonged anaerobic soil conditions typi- 

 cally lower the soil redox potential and causes a 

 chemical reduction of some soil components, main- 

 ly iron oxides and manganese oxides. This reduc- 

 tion affects solubility, movement, and aggregation 

 of these oxides which is reflected in the soil color 

 and other physical characteristics that are usually 

 indicative of hydric soils. (Note: Much of the back- 

 ground material for this section was taken from 

 "Hydric Soils of New England" [Tiner and Vene- 

 man 1987].) 



3.9. Soils are separated into two major types on 

 the basis of material composition: organic soil and 

 mineral soil. In general, soils with at least 18 inch- 

 es of organic material in the upper part of the soil 

 profile and soils with organic material resting on 

 bedrock are considered organic soils (Histosols). 

 Soils largely composed of sand, silt, and/or clay 

 are mineral soils. (For technical definitions, see 

 "Soil Taxonomy", U.S.D.A. Soil Survey Staff 

 1975). 



3.10. Accumulation of organic matter in most or- 

 ganic soils results from prolonged anaerobic soil 

 conditions associated with long periods of submer- 

 gence or soil saturation during the growing season. 

 These saturated conditions impede aerobic decom- 

 position (oxidation) of the bulk organic materials 

 such as leaves, stems, and roots, and encourage 

 tiieir accumulation over time as peat or muck. Con- 

 sequently, most organic soils are characterized as 

 very poorly drained soils. Organic soils typically 

 form in waterlogged depressions, and peat or muck 

 deposits may range from about two feet to more 



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