Redoximorphic Features Redoximorphic Features and Hydric Soilsand Hydric Soils

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

Redoximorphic Features Formed by changes in redox conditions in

saturated soil Reduction and oxidation of C, Fe, Mn, and

S compounds Translocation of C, Fe, Mn, and S

compounds

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

Redox TransformationsCoating of Fe2O3

Remove Fe

Brown Soil Fe3+

Fe2+

Gray Soil

2e- + 6H+ + Fe2O3 2Fe(II) + 3H2ONC STATENC STATE UNIVERSITY UNIVERSITY

DEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCENC STATENC STATE UNIVERSITY UNIVERSITY

DEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCENC STATENC STATE UNIVERSITY UNIVERSITY

DEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCENC STATENC STATE UNIVERSITY UNIVERSITY

DEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

Redox features are like M&Ms

=

In order to form features:

• must have anaerobic conditions (reduced and saturated)

• must have Fe and/or Mn (electron acceptor)

• must have microbes (bugs)

• must have carbon (food for the bugs)

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

Redoximorphic Features

• Redox concentrations – zone where Fe - Mn oxides have accumulated

• Redox depletions – zone where of Fe – Mn oxide have been stripped out

• Reduced matrix – low chroma matrix that changes color when exposed to air

Redox depletions (Fe depletions)

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

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Fe depletionsFe depletion on ped face

Fe depletion on pore

Fe depletion in ped interior

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

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Fe depletions

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Concentrations and depletionsConcentrations and depletions

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Redox concentrations (Fe masses, Fe pore linings)

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Fe masses and Fe pore linings

Pore lining on root channel

Pore lining on Ped surface

Nodule

Fe massin matrix

Concretion

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

Fe pore linings

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

Fe masses

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

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Reduction, oxidation and Reduction, oxidation and translocation = saturationtranslocation = saturation

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

1. Plant root grows into 1. Plant root grows into soilsoil2. Root dies and starts 2. Root dies and starts to decomposeto decompose

3. Water table rises3. Water table rises

4. Bacteria continue 4. Bacteria continue to decompose rootto decompose root

Oxygen reducedOxygen reduced

Nitrate reducedNitrate reduced

Fe reduced and Fe reduced and removed, soil turnsremoved, soil turns graygray

5. Reduced Fe moves 5. Reduced Fe moves away from decomposing away from decomposing rootroot

Reduced Fe oxidizes, Reduced Fe oxidizes, soil turnssoil turns redred

7. Root completely 7. Root completely decomposeddecomposed

6. Water drains from 6. Water drains from root channelroot channel

8. Water table drops8. Water table drops

Redox depletionRedox depletion

Redox Concentration Redox Concentration (Pore lining)(Pore lining)

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NC STATENC STATE UNIVERSITY UNIVERSITYDEPARTMENT of DEPARTMENT of SOIL SCIENCESOIL SCIENCE

Lithochromic mottle

Redox depletion

Concepts of Wetlands, Hydric Soils, and

Wetland Hydrology

What is a wetland?

Wetland Definition (as defined by FSA Manual and

COE 1987 Manual)

• has wetland hydrology

• has a predominance of hydrophytic vegetation

• the presence of hydric soil

Wetland hydrology occurs when:

• the water table is at or near the surface (12 inches) and,

• present for at least 5 percent (consecutive) of the growing season.

0

6

12

18

24

30

36

42

48

1 2 3 4 5 6 7 8 9 10 11 12

Month

Dep

th (

in.)

Determining Wetland Hydrology

Determining the Growing Season

• Use NRCS County Soil Survey for beginning and end dates

• Determine number of days in season

• Multiply by 0.05

• Usually between 12 and 14 days in this region

Definition of Hydric Soil

A hydric soil is a soil that formed under conditions of saturation,

flooding, or ponding long enough during the growing season to

develop anaerobic conditions in the upper part

Field Indicators of Hydric Soils

Field indicators of hydric soils are designed for on-site identification of

hydric soils

Field Indicators of Hydric Soils in the United States

Version 5.01