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refresher - Hydric Soils FINAL

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					       Hydric Soils

Wetland Delineation Certification Refresher
           General Information
• Soils consist of unconsolidated, natural
  mineral that supports, or is capable of
  supporting, plant life.
• Components that make up soil include:
  –   Sand;
  –   Silt;
  –   Clay; and
  –   Organic matter.
          General Information
• Most soils have 2 or more identifiable horizons,
  described from the surface downward.

• A soil horizon is a layer oriented approximately
  parallel to the soil surface, and is usually
  differentiated from contiguous horizons by
  characteristics that cam be seen or measured in the
  field (e.g. color, structure, texture, etc.).
               Typical Soil Horizons
                            Surface Organic Layer   O horizon
Area of primary interest                            A Horizon
                            Surface Mineral Layer
For delineation purposes.

                                   Subsoil          B Horizon


                                 Underlying         C Horizon
                                  Material


                                  Bedrock           R Horizon
A horizon


Bw horizon




C horizon
A horizon


E horizon


Bh horizon


Bs horizon
              Soil Horizons
• A horizon – Surface soil or topsoil:
  – Zone in which organic matter is usually being
    added to the mineral soil.
  – Zone from which both mineral and organic
    matter are being moved slowly downward.
  – Defined as having a value of 3 or less and a
    chroma of 2 or less.
                          Soil Colors
• Munsell Soil Color Book,
  7.5YR page.




                    A horizon
(Value 3 or less and Chroma 2 or less)
          Influencing Factors in
              Soil Formation
•   Climate
•   Parent Material
•   Relief
•   Organisms
•   Time
•   Hydrology – overriding factor for hydric soils.
                 Soil Color
• Soil colors are described as a combination
  of:
  – Hue (e.g. 10YR);
  – Value (e.g. 4/); and
  – Chroma (e.g. /1).

  Written as 10YR 4/1
                                 Hue
           Red


0   2.5R   5R 7.5R   10R
                              Yellow-Red


                           0 2.5YR 5YR 7.5YR 10YR
                                                       Yellow



                                                0   2.5Y   5Y 7.5Y   10Y
                 Value

                  • 10/0 - Pure White
The Lightness
or Darkness of
                  • 5/0 - “Gray”
Color

                  • 0/0 - Pure Black
                  Chroma
“Neutral”                                  “Pure”
  Color                                    Color



   /0        /2        /4        /6          /8

  Increasing strength of color




                     Increasing grayness
                Coloring Soils
• Optimum conditions
  –   Natural light;
  –   Clear, sunny day;
  –   Midday;
  –   Light at right angles;
  –   Soil moist.
    Describing Redox Features
• Matrix (predominant) color;
• Redox colors;
• Redox contrast, abundance, and size.
    Describing Redox Features
• Contrast                     • Abundance
  – Faint -- evident only        – Few -- less than 2%
    on close examination         – Common -- 2 to 20%
  – Distinct -- readily seen     – Many -- more than 20%
  – Prominent -- contrast
    strongly                   • Size
                                 – Fine -- < 5 mm
                                 – Medium -- 5 to 15 mm
                                 – Coarse -- > 15 mm
               Hydric Soils
• The hydric soil definition and criteria
  published in the 1987 Corps Manual are
  obsolete. Current hydric soil definition,
  criteria, and lists are available from the
  USDA at:

      http://soils.usda.gov/use/hydric/
       Hydric Soil Definition
• 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.

• Hydric soils support, or are capable of
  supporting, the growth and regeneration of
  hydrophytic vegetation.
        Hydric Soil Definition
• Hydric soils include those soils that are
  artificially wet.

• Hydric soils include those soils that are
  artificially drained, if the natural soil was
  hydric.
       Hydric Soil Definition
• Some series, designated as hydric, have
  phases that are not hydric depending on
  water table, flooding, and ponding
  characteristics.
        Criteria for Hydric Soils
• Four broad hydric soil criteria are:
   1.   Organic soils;
   2.   Mineral soils with high water tables;
   3.   Ponded soils;
   4.   Flooded soils.

• Hydric soil criteria were designed to
  generate a list of hydric soils from the
  national database.
• Except for criteria 3 and 4, they were not
  intended for field identification purposes.
      Criteria for Hydric Soils
Hydric Soil Criteria:
1. All Histels except Folistels, and Histosols
   except Folists;
2. Soils in Aquic suborders, great groups,
   or subgroups, Albolls suborder,
   Historthels great group, Histoturbels great
   group, Pachic subgroups, or Cumulic
   subgroups that are:
      Criteria for Hydric Soils
2a. Somewhat poorly drained with a water
    table equal to 0.0 foot (ft) from the surface
    during the growing season, or

    This criterion is an artifact of the way the
    soils database was populated over the
    years; artificially drained PD and VPD
    soils were called SWP in previous years.
       Criteria for Hydric Soils
2b. Poorly drained or very poorly drained and
  have either:
  i. Water table equal to 0.0 ft from the surface during the
     growing season if textures are coarse sand, sand, or fine
     sand in all layers within 20 inches, or for other soils
  ii. Water table at less than or equal to 0.5 ft from the
     surface during the growing season if permeability is
     equal to or greater than 6.0 inches / hr in all layers
     within 20 inches, or
  iii. Water table at less than or equal to 1.0 ft from the
     surface during the growing season if permeability is
     less than 6.0 inches / hr in any layer within 20 inches,
     or
    Criteria for Hydric Soils

3. Soils that are frequently ponded for
   long duration or very long duration
   during the growing season; or


4. Soils that are frequently flooded for
    long duration or very long duration
    during the growing season
          Hydric Soil Criteria
• Frequently – flooding, ponding, or saturation
  likely to occur often under usual weather
  conditions (>50 in 100 years).
• Ponded – water stands in closed depression.
• Flooded – soil surface temporarily covered with
  flowing water from any source.
• Long Duration – innundation for a single event
  ranges from 7 days to 1 month.
• Very Long Duration – innundation for a single
  event is greater than 1 month.
            Hydric Soil Lists
• A hydric soil list is an interpretative rating
  which must be confirmed by on-site
  investigation.
• Types of hydric soil lists:
   – National
   – State
   – Local or field office
  Local or field office lists have precedence
  over state and national lists.
    87 Manual Wetland Indicators
                 (Non-Sandy Soils)
• Indicators in descending order of reliability.
    a.   Organic soils (Histosols);
    b.   Histic epipedons;
    c.   Sulfidic material;
    d.   Aquic or peraquic moisture regime;
    e.   Reducing soil conditions;
    f.   Soil colors;
    g.   Soils appearing on hydric soils lists; and
    h.   Iron and manganese concretions.
    87 Manual Wetland Indicators
              (Non-Sandy Soils)
• Organic Soils
  (Histosols) – more
  than 50% of upper 32
  inches is organic
  material; or any
  organic material
  resting on bedrock.
87 Manual Wetland Indicators
       (Non-Sandy Soils)
                • Histic epipedon – an
                  8-16 inch layer of
                  organic material at, or
                  near, the surface of a
                  mineral hydric soil.
    87 Manual Wetland Indicators
               (Non-Sandy Soils)
• Sulfidic material –
  when mineral soils
  emit an odor of rotten
  eggs, hydrogen sulfide
  is present. Sulfides
  are produced only in a
  reducing environment.
    87 Manual Wetland Indicators
               (Non-Sandy Soils)
• Order of reducing reaction (fastest to slowest)
  Redox
  Potential Element Reaction
  +350 mV    Oxygen      O2 + 4H+ = 2H2O
  +220 mV    Nitrogen    2NO3- + 12H+ = N2 + 6H2O
  +200 mV    Manganese   MnO2 + 4H+ = Mn2+ + 2H2O
  +120 mV    Iron        Fe(OH)3 + 3H+ = Fe2+ + 3H2O
  -150 mV    Sulfur      SO42- + 10H+ = H2S + 4H2O
  -250 mV    Carbon      CO2 + 8H+ = CH4 + 2H2O
           87 Manual Wetland Indicators
                          (Non-Sandy Soils)
Subgroup - Great Group, Suborder, Order     • Aquic or peraquic
  4            3           2        1         moisture regime –
                                              An aquic moisture
   Vertic Udifluvent                          regime is a reducing
                                              one; a peraquic
• 4 – Vertic subgroup: High clay, shrink-
  swell.
                                              moisture regime is one
• 3 – Udi(c) great group: Humid climate.
                                              characterized by the
• 2 – Fluv(ic) suborder: Alluvial.            presence of ground
• 1 – Ent(isol) order: Minimal soil           water always at or
  development.                                near the surface.
Moisture regime information is
    found in the Suborder
   Soil Taxonomy Nomenclature
                     4     3 2 1
                   Typic Fluvaquents
•4 – Typic subgroup.
•3 – Fluv(ic) great group.
•2 – aqu(ic) suborder.
•1 – Ent(isol) order.

Typical4 Entisols1 with aquic2 moisture regimes
that occur on floodplains3.
   Soil Taxonomy Nomenclature
                  4      3 2 1
                Mollic Fluvaquents
•4 – Mollic subgroup.
•3 – Fluv(ic) great group.
•2 – aqu(ic) suborder.
•1 – Ent(isol) order.

Entisols1 with aquic2 moisture regimes that occur
on floodplains3 and have thick, dark surface
layers4.
     87 Manual Wetland Indicators
                   (Non-Sandy)
• Reducing soil
  conditions – reducing
  soil conditions as
  evidence by
  colorimetric field test,
  typically α,α’-dipyridl.
  Reduced iron reacts
  with the dye and
  results in a red
  coloration.
    87 Manual Wetland Indicators
                 (Non-Sandy)
• Soil colors – Soil color is often the most
  diagnostic indicators and include the
  following:
  – Gleyed soils – pronounced reduction of iron,
    managnese, and other minerals producing
    grayish, blueish, or greenish colors;
  – Soils with bright mottles and/or low matrix
    chroma.
     • Matrix of 2 or less in mottled soils;
     • Matrix of 1 or less in unmottled soils.
   87 Manual Wetland Indicators
            (Non-Sandy)
Gleyed         Mottled    Unmottled
  87 Manual Wetland Indicators
                (Non-Sandy)
• IMPORTANT NOTE:
 ! The statement in the 87 Manual that gleyed and
   low-chroma colors must be observed
   "immediately below the A-horizon or 10 inches
   (whichever is shallower)" is intended as
   general guidance.

 ! Certain “problem soils” may differ.
                Problem Soils
• Problem Soils as identified in 1992
  Clarification.
  –   Mollisols;
  –   Spodosols;
  –   Entisols;
  –   Red parent material.
    87 Manual Wetland Indicators
                     (Non-Sandy)
• “Problem Soils” may not exhibit typical
  soil color characteristics. Care must be
  taken when making hydric soil
  determinations in these areas.

• If a problem soil is present, follow the
  procedures outlined in:
  “Guidelines for Submitting Wetland Delineations to the St.
  Paul District Corps of Engineers and Local Units of
  Government in the State of Minnesota, (96-01078-SDE,
  April 17, 1996).”
    87 Manual Wetland Indicators
                  (Non-Sandy)
• Soils appearing on
  hydric soils lists –
  Using the criteria for
  hydric soils, the
  NTCHS has developed
  a list of hydric soils.
  Be sure that the
  mapped soil
  description matches
  the sampled soil.
87 Manual Wetland Indicators
         (Non-Sandy)
               • Iron and Manganese
                 concretions –
                 Concretions >2mm in
                 diameter and within
                 7.5cm of the surface
                 are evidence that the
                 soil is saturated for
                 long periods near the
                 surface.
     87 Manual Wetland Indicators
                    (Sandy Soils)
• Not all indicators can be applied to sandy
  soils, in particular, soil color should not be used
  as an indicator in most sandy soils.

• Additional indicators for sandy soils:
   – High organic matter content in surface horizon;
   – Streaking of subsurface horizons by organic matter;
     and
   – Organic pans.
    87 Manual Wetland Indicators
                   (Sandy Soils)
• High organic matter
  content in surface
  horizon: prolonged
  inundation or
  saturation creates
  anaerobic conditions
  that greatly reduce
  oxidation of organic
  matter causing it to
  accumulate above or
  in the surface horizon.
87 Manual Wetland Indicators
         (Sandy Soils)
                • Streaking of
                  subsurface horizons
                  by organic matter:
                  Organic matter is
                  moved downward
                  through sand as water
                  table fluctuates.
                  Sandy soil appears
                  vertically streaked
                  with darker areas.
    87 Manual Wetland Indicators
                   (Sandy Soils)
• Organic pans: As
  organic matter is
  moved downward
  through sandy soils, it
  tends to accumulate at
  the point representing
  the most commonly
  occurring depth to
  water table.
    87 Manual Wetland Indicators
                (Sandy Soils)
• In recently deposited sandy material (i.e.
  Entisols), it may be impossible to find any
  of these indicators. In such cases, consider
  this as a natural atypical situation.
• Entisols are identified as a “Problem Soil”.
• If a problem soil is present, follow the
  procedures in the St. Paul District Corps of
  Engineers guidelines.
 Additional Materials to Review
• In addition to the 87 Manual, delineators
  must also be familiar with the following
  publications:
  – Questions & Answers on 1987 Manual (CECW-OR,
    October 7, 1991);
  – Clarification and Interpretation of the 1987 Manual
    (CECW-OR, March 6, 1992); and
  – Guidelines for Submitting Wetland Delineations to the
    St. Paul District Corps of Engineers and Local Units of
    Government in the State of Minnesota (96-01078-SDE,
    April 17, 1996).
           Common Pitfalls
• Not sampling below the A horizon.
• Inconsistent hydric soil determinations.
• Calling drained hydric soils non-hydric.
• Using NRCS Field indicators in place of 87
  Manual criteria.
• Forgetting criteria 3 and 4 for hydric soils.
• Not recognizing and adjusting for problem
  soils (mollisols, entisols, and red parent
  material).

				
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