Altered Hydric Soils

1
Altered Hydric Soils

• by
• Wade Hurt, USDA, NRCS, NSSC/ University of
  Florida, Gainesville, FL, Chris Noble, USACE,
  Vicksburg, MS, and Victor Carlisle, University of
  Florida, Gainesville, FL.

2
Types of Altered Hydric Soils

• Artificial
• Drained (Protected)
• Historic
• Relict
• The objectives of this lecture are to outline
  criteria used to identify each of these
  alterations and to outline the impact of
  alterations on the hydric status of a soil.

3
Development of Altered Soils

• Hydrologic modification may result in
• 1. Artificial Hydric Soils
• 2. Drained (Protected) Hydric Soils.
• Soil modification may result in
• 1. Artificial Hydric Soils
• 2. Historic Hydric Soils
• 3. Relict Hydric Soils

4
Hydrologic Modification

• Hydrologic modification results where saturation
  and/or inundation (ponding or flooding) has been
  changed by human or geologic processes.
• Both geologic modifications and human
  modifications of hydrology may change the hydric
  status of a soil.

5
Soil Modification

• Soil modification result where soils (not
  hydrology) have been altered either through
  geologic or human additions or removals.
• Both geologic modifications and human
  modifications of a soil may change the hydric
  status of a soil.

6
Key

• Hydric Soils are currently supporting or capable
  of supporting wetland ecosystems. Soil
  modifications are not needed to maintain or
  restore a wetland. In the case of drained hydric
  soils, only removal of hydrologic modifications
  are needed to restore wetlands.
• Nonhydic soils currently are not supporting nor
  are they capable of supporting wetland
  ecosystems. Soil modifications are needed to
  create a wetland. Hydrology modifications may
  also create a wetland on nonhydric soils. The
  differences between creation and restoration will
  be discussed layer.

7
Review Why is a Soil Hydric

• A soil is hydric because it
• 1. Has a hydric soil indicator, or
• 2. Meets hydric soil criteria 3 or 4, or
• 3. By data meets the Hydric Soil
  Technical Standard (HSTS).

8
Artificial Hydric Soils

• Wetness of these altered soils has been increased
  by human activities (constructed wetlands,
  irrigation leaks, rice fields, lake skeins and
  other construction activities) or the soils have
  been altered by human activities (constructed
  wetlands, pond fringes and other excavations).
• These altered soils are hydric soils because
  they
• 1. Have a hydric soil indicator, or
• 2. Meet hydric soil criteria 3 or 4, or
• 3. By data meet the HSTS.

9
Artificial Hydric Soil
This dug pond has an artificial hydric soil
fringe that was created when the pond was
constructed. It now supports a wetland ecosystem.
10
Artificial Hydric Soil
The wetland shown here and on the first slide was
created by removing soil material from a
nonhydric soil. The resulting soil is an
Artificial Hydric Soil.
11
Artificial Hydric Soil
Construction activities, note the railroad in the
background, may be the reason wetlands and hydric
soils exist here.
12
Drained (Protected) Hydric Soils

• This is the 2nd type of altered hydric soils An
  attempt through human activities to decrease the
  wetness of these altered soils has been made
  (ditches, levees, dams, pumps, etc.).
• Even with reduced wetness these altered soils
  maintain their hydric status because they
• 1. Have a hydric soil indicator or,
• 2. Meet hydric soil criteria 3 or 4 or,
• 3. By data meet the HSTS.

13
Ditches, levees, dams, pumps, etc., do not alter
the hydric status of a soil.
14
Drained Hydric soils

• The concept of drained hydric soils maintaining
  their hydric status should be thoroughly
  understood. This is important to wetland
  scientist. By recognizing a soil with a hydric
  soil indicator as being hydric regardless of
  hydrologic alteration we keep soils capable of
  supporting wetlands (if hydrology was restored)
  in the same class as soils that are currently
  supporting wetlands.
• I have seen areas ditched, pumped, and protected
  by levees in the Mississippi delta that are in
  crop production (soybeans) that are still not
  drained hydric soils because they still pond
  water for up to one month during the growing
  season, still have a hydric soil indicator, and
  still meet the HSTS. One can hardly never
  underestimate the effect of ditches upon the
  hydric status of a soil.
• In normal circumstances a wetland requires the
  presence of three criteria (wetland hydrology,
  wetland vegetation, and hydric soils). For an
  area to be a wetland each of these criteria are
  met independently.

15
Historic Hydric Soils

• This is the 3rd type of altered hydric soils
  These altered soils have had additional soil
  material placed on top of the original soil by
  human activities to the extent that that they are
  no longer hydric (1993 flooding deposition on the
  Missouri River flood plain, filling a wetland).
  The additions may be intentional (illegal fill)
  or non intentional (erosional deposition).
• These altered soils are nonhydric because they
• 1. Do not have a hydric soil indicator and,
• 2. Do not meet hydric soil criteria 3 or 4 and,
• 3. Do not, by data, meet the HSTS.

16
Historic Hydric Soils are altered soils that were
once hydric but have had human modifications
(additions) such that they are no longer hydric.
The additions may be intentional (illegal fill)
or non intentional (erosional deposition).
Nonhydric Hydric
15 cm
17
Historic Hydric Soils

• Even though fill material has been placed over
  the entire soil area shown in the previous slide
  it has areas that are still hydric as well as
  areas that are no longer hydric. The area to the
  right of the vertical arrow is still hydric even
  though fill material has been placed on the
  surface it has the HS Indicator S6 (Stripped
  Matrix) starting within 15 cm (6 inches) of the
  surface. The lower horizontal arrow indicated
  where the stripped matrix starts. The soil area
  to the left of the vertical arrow still has a
  stripped matrix but it starts below the depth
  required (15 cm) by the HS Indicator S6 (Stripped
  Matrix).
• Can you think of other ways (other than the
  presence of a HS Indicator) that a soil can be
  proven to be hydric? What about monitoring to
  see if it floods or ponds long enough to satisfy
  Criteria 3 or 4 or monitoring to see if it meets
  the HSTS?

18
Areas which may have changed from hydric to
nonhydric.
Channelization and the resulting spoil may change
the hydric status of a soil. Also the
surrounding area may have reduced wetness.
Culvert
19
Historic Hydric or Still Hydric?
Depleted Matrix starts here
20
Historic?

• The soil in the previous slide has had fill
  material placed over the original soil. The knife
  blade points to the limit of the 10YR 5/4 fill
  material (24 cm). The blue arrow points to the
  start of HS indicator F3, Depleted Matrix (28
  cm). This new soil is nonhydric because the
  depleted matrix does not start within 25 cm and
  because the fill material has a chroma of 4. This
  is a Historic Hydric Soil.
• What if the same fill material was only 18 cm
  thick over the same underlying soil? This means
  the depleted matrix would start at 22 cm. Would
  the soil be hydric or nonhydric? This new soil
  would still be nonhydric. Remember the
  introductory Unless otherwise indicated,all
  mineral layers above any of the Indicators have
  dominant chroma 2 or less,or the layer(s)with
  dominant chroma of more than 2 is less than 15 cm
  (6 in)thick (Hurt, et al. 2002, p.5). It would
  still be a Historic Hydric Soil.
• In this example the fill material would have to
  be less than 15 cm (6 in) thick for the soil to
  be a hydric soil.

21
Relict Hydric Soils

• This is the 4th type of altered hydric soils
  These altered soils were once hydric but are no
  longer hydric due to geologic activities (pimple
  mounds of Texas Gulf Coast Prairie, stream
  downcutting).
• Only on close examination is it evident that
  hydric soil morphologies do not exist.
• These altered soils are nonhydric because they
• 1. Do not have a hydric soil indicator and,
• 2. Do not meet hydric soil criteria 3 or 4 and,
• 3. Do not, by data, meet the HSTS.

22
Relict Hydric Soils

• Several morphological characteristics can suggest
  relict redoximorphic features (Vepraskas, 1994).
  These are
• 1. Feature type and boundary characteristics,
• 2. Location to macropores,
• 3. Redox feature color, and
• 4. Pore lining continuity.

23
1. Feature and Boundary Characteristics

• A. Nodules and concretions
• B. Other redox concretions.

24
1 A Nodules and Concretions Feature and Boundary
Characteristics

• Contemporary nodules and concretions have
• 1. Diffuse boundaries (the color grade is
  commonly more than 2 mm wide),
• 2. Irregular surfaces, and
• 3. If smooth and round surfaces, red to yellow
  corona (halos) should be present.
• Relict nodules and concretions may have
• 1. Sharp boundaries (color grade is commonly less
  than 0.1 mm wide) and
• 2. Smooth surfaces.

25
Relict Features
These redoximorphic features (nodules) most
likely are relict because they have sharp
boundaries and smooth surfaces. (photograph
Vepraskas. 1994)
26
1 B Other Redox Concentrations Feature and
Boundary Characteristics

• Contemporary redox concentrations have diffuse
  boundaries.
• Relict redox concentrations may have sharp
  boundaries.

27
Contemporary redox concentrations have diffuse
boundaries. Relict redox concentrations may have
sharp boundaries.
3 cm
1 cm
28
2 Redox Macropore Features

• Contemporary macropores may have
• Fe depletions along stable macropores in which
  roots repeatedly grow that are not overlain by
  iron rich coatings.
• Relict macropores may have
• Fe depletions along stable macropores in which
  roots repeatedly grow that are overlain by iron
  rich coatings.

29
3 Redox Color Features

• Contemporary redox colors may be the results of
  the iron minerals
• 1. Ferrihydrite (5YR), Lepidiocrocite (7.5YR),
  Goethite (7.5YR, 10YR), and Jarosite (2.5Y) and
• 2. Have value and chroma 4 or more.
• Relict redox colors may be the results of the
  iron mineral
• 1. Hematite (10R, 5R, 2.5YR) and
• 2. Have value and chroma lt4.

30
4 Pore Lining Continuity

• Contemporary pore linings may be continuous
  especially around living roots. Relict pore
  linings may be broken and unrelated to live
  roots.
• Pictured below is a continuous pore lining
  (reddish area) parallel to a reduced area
  (blue-green).

31
Relict Hydric Soils Texas Gulf Coast Prairie
Present Land Surface Geologic Land Surface
Geologic Hydric Soil Boundary
Telferner
Present Hydric Soil Boundary
2m
Nada, Dry
Nada, Wet
0-10 cm lfs 10YR 5/3 10-29 cm sc 10YR 5/2 cd
10R 3/3
Cieno
0-19 cm fsl 10YR 4/2 19-27 cm scl 10YR 4/2 fd
7.5YR 4/6
0-12 cm fsl 10YR 4/2 12-29 cm scl 10YR 4/2 cd
7.5YR 4/6
0-10 cm l 10YR 5/3 cd 7.5YR 4/6 10-25 cm sl
10YR 5/2 cd 7.5YR 4/6
cd common distinct fd few distinct
32
Relict Hydric Soils Texas Gulf Coast Prairie

• The landscape depicted in the previous slide
  shows an area where climatic changes have made
  what once was the lowest area (Telferner soils)
  is now the highest area. Only by close
  examination do we know that the Telferner soils
  are now relict hydric soils the redox
  concentrations are 10R 3/3. cd common distinct
  and fd few distinct

33
Redox features forming
Original surface
Fill
34
Time and the formation of redox features

• The soil shown on the previous slide has fill
  material about 10 inches thick placed over the
  original soil that had a depleted matrix.
• The fill material had been in place for only a
  few years and redox features are forming in the
  lower ½ of the fill material indicating that in a
  few more years a hydric soil indicator would be
  present in the new soil.

35
Summary

• The types of Altered Hydric Soils are Artificial,
  Drained (Protected), Historic, and Relict hydric
  soil. Artificial hydric soils were once nonhydric
  but now are hydric soils created by human
  modifications to hydrology (additional water) or
  soil (removal of soil). Drained hydric soils
  were hydric and still are hydric soils created
  by human modifications to hydrology. Historic
  hydric soils were once hydric but are now
  nonhydric soils created by geologic or human
  modifications to soils (additions). Relict hydric
  soils were hydric but are now nonhydric soils
  created by geologic modifications to hydrology.
• A soil is hydric because it (1) Has a hydric
  soil indicator or, (2) Meets hydric soil criteria
  3 or 4 or, (3) By data meets the HSTS.

36
Caveats

• Modified soil and hydrology may be due to illegal
  or legal activities.
• By federal or state agency policy, modified areas
  may be subject to litigation (Section 404 CWA,
  Swampbuster) or still eligible for programs
  (USDAs EWP).

37
Literature Cited

• 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.pd
  f
• Vepraskas, M. J. 1994. Redoximorphic Features for
  Identifying Aquic Conditions. Tech. Bulletin 301.
  North Carolina Ag. Research Service, North
  Carolina State Univ., Raleigh, North Carolina.