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Field Identification of Hydric SoilsFor

Wetland Delineation

Colleen L. FilipponeSWES 574

The University of ArizonaNovember 2002

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Wetland (hydric) Soils: Soils that formed under conditions of saturation, flooding or ponding long enough during

the growing season to develop anaerobic conditions in the upper part (Federal Register, 1994).

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Wetland Delineation

• 1985 Food Security Act definition– Hydrophytic vegetation– Hydric soils– Hydrology

• COE Wetlands Delineation Manual 1987

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Hydric Soil Criteria and Indicators

National Technical Committee for Hydric SoilsU.S.D.A. N.R.C.S. Soils Division

Wetland Science Institute

Criteria

1. All Histosols except Folists2. Soils classified as Aquic, Albolls,

Aquisalids, Pachic or Cumulic that meet certain requirements

3. Frequently ponded soils4. Frequently flooded soils

Field Indicators

1. Characteristic morphologies originating in and as a result of biogeochemical processes under anaerobic conditions

2. Persist under saturated or unsaturated conditions

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Soil Science Basics

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Redox and depletionProcesses

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Redox Potential and Dominant Hydric Soil Indicator forming processes:

1. Accumulation or loss of iron, manganese, sulfur or carbon2. Presence of hydrogen sulfide gas3. Accumulated organic carbon (for soils formed from

parent materials low in Fe/Mn)

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Method:1. Choose transect and measure2. Remove loose and easily identifiable plant parts (iduffi layer)3. Dig hole to at least 50 cm, often deeper is required4. Specify which indicators have been matched

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Hydric Indicators for All Soils

A1. Histosols (wet) except Folists

A3. Black Histic10 YR or yellower

Value <3; Chroma <1

A4. Hydrogen Sulfide odor within 30 cm of

surface

A5. Stratified layers with thickness and color requirements

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A7-10. Muck (thickness and color requirements)

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A6. Organic bodies between 0 and 10 cm, dark surface, percent organic carbon requirements.

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Hydric Indicators for Sandy Soils

S4. Sandy gleyed matrix(specific color requirements) S6. Stripped matrix

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S5. Sandy Redox

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Hydric Soil Indicators for Loamy and Clayey Soils

F2. Loamy gleyed matrix F3. Depleted matrix

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F4. Depleted below dark surface F5. Thick dark surface

Hydric Soil Indicators for Loamy and Clayey Soils

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F6. Redox dark surface

Hydric Soil Indicators for Loamy and Clayey Soils

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F12. Iron/manganese masses

Fe, Mn and carbon indicators

Redox Features

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References

Hurt, G.W. and J.L. Richardson. Hydric Soils of the United States A Guide to Their Recognition. U.S.D.A., N.R.C.S., Soils Division, Wetlands Science Institute, National Technical Committee for Hydric Soils.

Richardson, J.L. and M.J. Vepraskas, (eds.). 2001. Wetland Soils Genesis, Hydrology, Landscapes, and Classification. CRC Press LLC. Boca Raton.

U.S. Department of Agriculture, Natural Resources Conservation Service. 1998. Field Indicators of Hydric Soils in the United States. Ver. 4.0. Hurt, G.W., P.M.Whited and R.F. Pringle (eds). USDA, NRCS Ft. Worth, TX.

Vepraskas, M.J. 1995. Redoximorphic Features for Identifying Aquic Conditions. North Carolina Agricultural Research Service Technical Bulletin 301. North Carolina State University. Raleigh, NC.