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Hydric Soil Indicators for Delineation

Hydric Soil Indicators for Delineation. by: Wade Hurt, USDA, NRCS, NSSC, Gainesville, FL, Chris Noble, USACE, Vicksburg, MS, and Victor Carlisle, University of Florida, Gainesville, FL. Introduction.

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Hydric Soil Indicators for Delineation

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  1. Hydric Soil Indicators for Delineation • by: Wade Hurt, USDA, NRCS, NSSC, Gainesville, FL, Chris Noble, USACE, Vicksburg, MS, and Victor Carlisle, University of Florida, Gainesville, FL.

  2. Introduction • The NTCHS approves hydric soil indicators for use in wetland identification and delineation as published in Field Indicators of Hydric Soils in the US (Hurt, et al. 2002). • Interior (wettest of wet) and boundary(delineation) indicators are not differentiated in the publication. • To facilitate use of HS indicators, wetland delineators need to know which indicators are the delineators and an understanding of the likely soil morphologies they would encounter inside and outside hydric soil boundaries. • This lecture differentiates interior and boundary indicators and describes likely soil morphologies at the delineation edge (Hurt and Carlisle. 2001).

  3. Interior: A1 A2 A3 • A1 (Histosols), A2 (Histic Epipedon), and A3 (Black Histic) are interior indicators. • A8, A9, A10, S2, and S3 are the boundary indicators used where organic soil materials are present. • Caution: A1 and A2 have Soil Taxonomy (Soil Survey Staff, 1999) requirements, however, you now understand that to delineate hydric soils a working knowledge of soil taxonomy is not a requirement.

  4. Interior: A4 S4 F2 • A4 (Hydrogen Sulfide), S4 (Sandy Gleyed Matrix, and F2 (Loamy Gleyed Matrix) are interior indicators. • “Rotten egg” odor and gleying show the soils are very reduced and identify only the wettest of the wet. Be especially careful to not misapply the hydrogen sulfide indicator. Soils produce other odors, specifically mercaptans. Mercaptans are sulfur-containing organic compound, especially ethyl mercaptan which is also and also called thinol. They are not hydrogen sulfide.

  5. Boundary: A5 • A5 (Stratified Materials) is routinely used to delineate hydric soils on flood plains and some flats. • Usually soils on the non hydric side of delineations are also stratified but chroma in one or more of the layers is 3 or more. • The next slide shows two soils. The one on the left fits the indicator A5 by having several strata within 15 cm all of which have chroma 2 or less and one or more of the strata have chroma of 3 or less and value 1 or less. The soil on the right (located about 2 meters upland from the other soil) fails A5 by having strata of chroma 3 or more.

  6. Boundary: A5

  7. Boundary: A6 • A6 (Organic Bodies) is routinely used to delineate hydric soils on flats of the Southern United States and Puerto Rico and as far north as New Jersey. • Soils on the non hydric side of delineations usually have organic accreted areas but they lack the required amount of organic carbon. • The soil material shown on the next slide has organic bodies. Only by texturing the bodies would you know if the required amount of carbon is present. If gritty the bodies would fail to have the required amount of carbon.

  8. Boundary: A6

  9. Boundary: A7 S1 F1 • A7 (5 cm Mucky Mineral), S1 (Sandy Mucky Mineral), and F1 (Loamy Mucky Mineral) are used to delineate hydric soils of flats and depressions. • Soils on the non hydric side of delineations have surface layers that lack the required amounts of organic carbon. • Much like the boundary indicator A6, these indicators require a certain amount of organic carbon. The soils on each side of delineation lines look very similar; only by texturing the bodies would you know if the required amount of carbon is present. If gritty the material would fail to have the required amount of carbon.

  10. Boundary: A8 A9 A10 S2 S3 • A8 (Muck Presence), A9 (1 cm Muck), A10 (2 cm Muck), S2 (2.5 cm Mucky Peat or Peat), and S3 (5 cm Mucky Peat or Peat) are used to delineate hydric soils of flats and depressions. • Soils on the non hydric side of delineations have surface layers that lack the required amount of organic carbon. In most locations the soils outside delineations established by these indicators not only lack the thickness requirements of these indicators they also lack any of the required material. • Much like the previously mentioned 4 indicators, these indicators require a certain amount of organic carbon. The soils on each side of delineation lines look very similar; only by texturing the bodies would you know if the required amount of carbon is present. If gritty the material would fail to have the required amount of carbon. The next slide shows the amount of carbon requires for A6, A7, A8, A9, A19, S1, and S2. • S2 and S3 are used in only 4 LRRs. In other LRRs mucky peat and peat have no relationship to the hydric status of a soil. The slide after the next shows a soil with about 5 cm of mucky peat (hemic soil material).

  11. P E R O R G A N I C S O I L M A T E R I A L C A S R E Q U I R E D BY E 18 I N D I C A T O R S N A 8 A 9 A 10 S 2 S 3 T O R G 12 M U C K Y M I N E R A L A S O I L M A T E R I A L N A S R E Q U I R E D BY I A 6 A 7 S 1 F 1 C C A 05 R M I N E R A L S O I L M A T E R I A L B O N 00 10 20 30 40 50 60+ P E R C E N T C L A Y

  12. Indicator S2 is for use in LRRs G and H only; indicator S3 is for use in LRRs F and M only. In other LRRs mucky peat and peat have no relationship to the hydric status of a soil.

  13. Boundary: A11 F3 F6 F7 • A11 (Depleted Below Dark Surface), F3 (Depleted Matrix), F6 (Redox Dark Surface), and F7 (Depleted Dark Surface) are used to delineate most types of wetlands throughout the U.S. • Soils on the nonhydric side of delineations usually lack chroma 2 or less or lack the required amounts of redox features. Or layers above the depleted matrix with chroma 3 or higher is more than 15 cm thick (next slide).

  14. This soil meets all the requirements of indicator F3 (depleted matrix with a depleted matrix starting within 25 cm (knife point) except the layers above the depleted matrix with chroma 3 or more are more than 15 cm thick. This soil is therefore nonhydric.

  15. Interior: A12 F16 • A12 (Thick Dark Surface) and F16 (High Plains Depression) are not normally used to delineate hydric soils. • These indicators normally occur inside the delineation line established by A11, F3, F6, F7, or F13 (normally A11 and F3 which are the most uses delineation indicators in the U.S.). • A12 has been used for delineation purposes in the Mollisol country in the Midwestern US, but only where construction activities have obliterated the natural hydric soil boundaries.

  16. Boundary: F8 F9 • F8 (Redox Depressions) and F9 (Vernal Pools) are used to delineate hydric soils that occur in closed depressions throughout the US. • Soils on the non hydric side of delineations usually lack any redox features. • Delineations created by these two indicators are perhaps some of the more obvious in the US. Soils on the nonhydric side show almost no evidence of reduction/anaerobiosis.

  17. Boundary: F10 • F10 (Marl) is used to delineate hydric soils in Southern Florida. • Soils on the non hydric side of delineations may meet all the requirements of marl but the value is less than 5 or they are the dry Histosols (Folists). • Wetland delineators, when first attempting to delineate based on this indicator, often become confused and may stay confused until they reread and understand. “Normally marl is the soil surface. No thickness is required” (Hurt, et al. 2002).

  18. Indicators A13 A14 A15 F11 F17 • The utility of these indicators are unknown.No information on the utility of these indicators have been provided to the NTCHS and the authors are unaware of their usefulness.

  19. Boundary: F12 F13 • F12 (Iron/Manganese Masses) is used to delineate hydric soils on flood plains throughout the US. F13 (Umbric Surface) is used to delineate hydric soils dominantly in the Southern US. Note that these indicators have landform restrictions. • Soils on the non hydric side of delineations created by F12 usually lack the required redox features within the required depths. Soils on the non hydric side of delineations created by F13 usually lack the required value or the layer is too thin. Examples of soils which meet these two indicators are provides on the next slide.

  20. Soils that meet indicators F12 (left) and F13 (right)

  21. Boundary: S5 S6 S7 • S5 (Sandy Redox), and S6 (Stripped Matrix) are used to delineate hydric soils throughout the US. S7 (Dark Surface) is used to delineate hydric soils on flats dominantly in the Southern US. • Soils on the non hydric side of delineations created by S5 and S6 usually lack the required redox features within the required depths. See the next slide for an example. • Soils on the non hydric side of delineations created by S7 usually have a salt and pepper appearance (see the second slide following) or the layer is too thin (see the third slide following form an example).

  22. The soil on the right has the indicator S6 starting within 15 cm of the surface and therefore is a hydric soil; the soil on the left has a stripped matrix starting below 15 cm and therefore is a nonhydric soil. The distance that separated these two soils was about 2 meters. Note that the hemic material above the mineral soil per instructions in Field Indicators of Hydric Soils in the US (Hurt, et al. 2002) was not considered when the hydric status of these soils was ascertained.

  23. This soil fails to have the required 10 cm of material that at least 70% covered, coated, or otherwise masked with organic material. It is “salt and pepper” at the surface and has the required coatings only from about 6 to 9 cm. This soil is nonhydric.

  24. The soil on the right has the indicator S7 with at least 10 cm of material that has at least 70 percent covered, coated, or otherwise masked with organic materials and therefore is a hydric soil; the soil on the left has the required material but it is less than 10 cm thick and therefore fails to meet the indicator S7. Note that the soil on the left is still a hydric soil; it meets indicator S9 (Thin Dark Surface).

  25. Interior: S8 S9 • S8 (Polyvalue Below Surface and S9 (Thin Dark Surface) are not normally used to delineate hydric soils. • These indicators normally occur inside the delineation line established by S5, S6, and S7. • In LRRs R and S they may, in certain locations, be delineation indicators.

  26. Regionalization • Now that we have separated the indicators based on their utility for delineation nationwide from those not used lets look at some specific LRRs to see if we can produce a more manageable listing. • The indicator use list for LRRs P,T, and U (Hurt and Vasilas. 2006) are: • P: A1, A2, A3, A4, A5, A6, A7, A9, A11, A12, S4, S5, S6, S7, F2, F3, F6, F8, F12, and F13. • T: A1, A2, A3, A4, A5, A6, A7, A9, A11, A12, A16 (MLRA 150A), S4, S5, S6, S7, S8, S9, F2, F3, F6, F8, F 11 (MLRA 151), F12, F13, F17 (MLRA 151), F18 (MLRA 150), and F20 (MLRAs 153C and 153D). • U: A1, A2, A3, A4, A5, A6, A7, A8, A11, A12, S4, S5, S6, S7, S8, S9, F2, F3, F6, F10, and F13. • By eliminating the interior indicators, those with unknown or limited utility, and the test indicators we arrive at the delineation indicators. • P: A5, A6, A7, A9, A11, S5, S6, S7, F3, F6, F8, F12, and F13. • T: A5, A6, A7, A9, A11, S5, S6, S7, F3, F6, F8, F12, and F13. • U: A5, A6, A7, A8, A11, S5, S6, S7, F3, F5, F6, F10, and F13.

  27. Regionalization/Minimization • From the information provided in the previous slide and if our interest is delineation, we can eliminated 6 indicators from the total list for LRR P, 10 from LRR T, and 6 from LRR U. Now we have a more manageable number of indicators with which we need to become familiar. There 12 delineation indicators for LRRs T and P and they are the same indicators. There are 13 delineation indicators for LRR U and they are the same as LRRs P and T except for muck thickness (A8 Vs A9) and the addition of A10 (marl). • Twenty indicators are for use or testing in California’s LRR C. Of these, seven identify very wet conditions (A1, A2, A3, A4, S4, F2, and F5) and four (F4, F6, F7, and TF7) are for very dark Mollisols which are rare in LRR C. Therefore the number of indicators with which one must become proficient is nine for all of LRR C. If one's area of interest is the Sacramento and San Joaquin Valleys, the number of indicators needed is only four (F3, F8, F9, and F12).

  28. Regionalization/Minimization • Twenty of the national indicators are identified for use in LRR N, an area that includes all or parts of Arkansas, Missouri, Alabama, Georgia, North and South Carolina, Tennessee, Kentucky, Virginia, West Virginia, Pennsylvania, Maryland, Ohio, and Indiana. Of these 20, seven occur only in very wet areas (A1, A2, A3, A4, A12, S4, and F2) and are not needed to delineate wetlands. Of the remaining thirteen, three (A12, F6, and F7) are useful only for delineating wet Mollisols, three (A10, S1, and F1) are for delineating muck or mucky soils, three others (S5, S6, S7) are for sandy soils only, and one (F13 is for use in a small area). Wet Mollisols, muck, mucky, and sandy soils are rare in LRR N. Therefore, to delineate most hydric soils in LRR N the number of indicators with which one must become proficient is four (A5, F3, F8, and F12).

  29. Summary • The NTCHS approves hydric soil indicators for use in wetland identification and delineation. • Interior (wettest of wet) and boundary(delineation) indicators have been differentiated. • Soil morphologies inside and outside hydric soil boundaries have been described. • 10 of the 45 indicators (A1, A2, A3, A4, S4, S8, S9, F2, F5, and F16) approved for use by the NTCHS are rarely used for delineation purposes. • 22 of the indicators (A5, A6, A7, A8, A9, A10, S1, S2, S3, S5, S6, S7, F1, F3, F4, F6, F7, F8, F9, F10, F12, and F13) are routinely used for delineation purposes. • The utility of 4 of the indicators (S10, F11, F14, and F15) is unknown. • By applying what we learned in this lecture we can seriously reduce the number of indicators with which we need to become familiar.

  30. Literature Cited • Hurt, G. W. and V.W. Carlisle. 2001. Delineating hydric soils. In Wetland Soils: Their Genesis, Morphology, Hydrology, Landscapes and Classification. J.L. Richardson and M.J. Vepraskas, (Eds.) Lewis Publishers, Boca Raton, FL. • Hurt, G.W. and L.M. Vasilas ( Eds.). 2006. Field indicators of hydric soils in the United States (Version 6.0), USDA, NRCS, Fort Worth, TX. http://soils.usda.gov/soil_use/hydric/field_ind.pdf • Soil Survey Staff. 1999. Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys. USDA Agricultural Handbook 436. US Govt. Printing Off., Washington, DC. http://soils.usda.gov/classification/taxonomy/main.htm

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