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Redoximorphic Features and Hydric Soils

NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE. Redoximorphic Features and Hydric Soils. NC STATE UNIVERSITY

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Redoximorphic Features and Hydric Soils

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  1. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Redoximorphic Features and Hydric Soils

  2. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL 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

  3. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Redox Transformations Coating of Fe2O3 Remove Fe Fe2+ Gray Soil Brown Soil Fe3+ 2e- + 6H+ + Fe2O3 2Fe(II) + 3H2O

  4. Redox features are like M&Ms =

  5. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE 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)

  6. 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

  7. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Redox depletions (Fe depletions)

  8. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Fe depletions Fe depletion in ped interior Fe depletion on ped face Fe depletion on pore

  9. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Fe depletions

  10. Concentrations and depletions NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE

  11. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Redox concentrations (Fe masses, Fe pore linings)

  12. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Fe masses and Fe pore linings Fe mass in matrix Pore lining on root channel Pore lining on Ped surface Concretion Nodule

  13. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Fe pore linings

  14. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Fe masses

  15. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Reduction, oxidation and translocation = saturation

  16. NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE Redox Concentration (Pore lining) 1. Plant root grows into soil 5. Reduced Fe moves away from decomposing root Reduced Fe oxidizes, soil turnsred 2. Root dies and starts to decompose 3. Water table rises 4. Bacteria continue to decompose root Oxygen reduced Nitrate reduced Fe reduced and removed, soil turnsgray 6. Water drains from root channel 7. Root completely decomposed 8. Water table drops Redox depletion

  17. Redox depletion Lithochromic mottle

  18. Concepts of Wetlands, Hydric Soils, and Wetland Hydrology

  19. What is a wetland?

  20. 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

  21. 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.

  22. Determining Wetland Hydrology Month 1 2 3 4 5 6 7 8 9 10 11 12 0 6 12 18 Depth (in.) 24 30 36 42 48

  23. 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

  24. 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

  25. Field Indicators of Hydric Soils Field indicators of hydric soils are designed for on-site identification of hydric soils

  26. Field Indicators of Hydric Soils in the United States Version 5.01

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