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Hydric Soils Technical Note 2

Changes to "Field Indicators of Hydric Soils in the United States" (Version 3.2, July 1996).

Send comments to Wade Hurt.

The NTCHS met in Corvallis, Oregon in July 1997 and made the following changes.

Change 1: Inside cover, Forward, last sentence is changed to "In 1995, the National Technical Committee for Hydric Soils (NTCHS) recommended that this document be distributed to all interested governmental agencies, universities, groups, and individuals involved in wetland delineation for use, testing and research on wet soils and, in 1996, assumed formal responsibility for the further development, revision, and publication of this document."

Change 2: Page 1, Concepts: 3rd paragraph, last sentence is changed to "Some of these carbon accumulation features, such as Indicator A1 ... are rarely used for delineation purposes."

Change 3: Page 10, S5, Sandy Redox, first sentence is changed to "A layer starting within 15 cm (6 in.) of the soil surface that is at least 10 cm (4 in.) thick, and has a matrix with 60% or more chroma 2 or less with 2% or more distinct or prominent redox concentrations as soft masses and/or pore linings."

Change 4: Page 11, S7, Dark Surface, last sentence is changed to "The matrix color of the layer immediately below the dark surface must have chroma 2 or less."

Change 5: Page 11, S7, Dark Surface, User Notes, last sentence is changed to "Where the percent of covered or coated soil particles is less than 70 percent, a Dark Surface indicator is not present."

Change 6: Page 13, F3, Depleted Matrix, User Notes. First sentence is changed to "Redox concentrations including iron and manganese soft masses and/or pore linings are required in soils with matrix colors of 4/1, 4/2, and 5/2." Add the following sentence "A, E, and calcic horizons may have low chromas and high values and may therefore be mistaken for a depleted matrix; however, they are excluded from the concept of depleted matrix unless common or many, distinct or prominent redox concentrations as soft masses or pore linings are present."

Change 7: Page 13, F3, Depleted Matrix, User Notes, this sentence is added "The minimum thickness requirement is 2 in. if the depleted matrix is within the upper 15 cm (6 in.) of the mineral soil surface."

The complete User Notes for F3 would then read as follows:

Depleted Matrix User Notes: The depleted matrix must begin within 25 cm (10 in.) and continue for at least 15 cm (6 in.). The minimum thickness requirement is 5 cm (2 in.) if the depleted matrix is within the upper 15 cm (6 in.) of the mineral soil surface. Redox concentrations including iron/manganese soft masses and/or pore linings are required in soils with matrix colors of 4/1, 4/2, and 5/2. A, E, and calcic horizons may have low chromas and high values and may therefore be mistaken for a depleted matrix; however, they are excluded from the concept of depleted matrix unless common or many, distinct or prominent redox concentrations as soft masses or pore linings are present. See glossary for the complete definition of depleted matrix. The low chroma matrix must be due to wetness and not a relict or parent material feature.

Change 8: Pages 14, 15, and 16. The following two sentences are to be added to the User Notes of F4 (Depleted Below Dark Surface), F5 (Thick Dark Surface), and F9 (Vernal Pools): "Redox concentrations including iron/manganese soft masses and/or pore linings are required in soils with matrix colors of 4/1, 4/2, and 5/2. A, E and calcic horizons may have low chromas and high values and may therefore be mistaken for a depleted matrix; however, they are excluded from the concept of depleted matrix unless common or many, distinct or prominent redox concentrations as soft masses or pore linings are present."

Change 9: Page 16, F13, Umbric Surface, First sentence is changed to "In depressions and other concave landforms, a layer 15 ..."

Change 10: Page 17, F16, High Plains Depressions, First sentence is changed to "In closed depressions subject to ponding, the presence of a layer at least 10 cm (4 in.) thick within the upper 35 cm (13.5 in.) of the mineral soil; the entire 35 cm (13.5 in.) has chroma 1 or less and:

a. 1% or more redox concentrations as nodules or concretions, or

b. redox concentrations as nodules or concretions with distinct or prominent corona."

Change 11: Page 17, F16, High Plains Depression, Third sentence is changed to "The matrix color of the 35 cm (13.5 in.)  layer must be a chroma 1 or less; chroma 2 matrix colors are excluded; value is usually 3."

Change 12: Page 19, TF2, Red Parent Material, first sentence is changed to "In parent material with a hue of 7.5YR or redder, a layer at least 10 cm (4 in.) thick with a matrix value 4 or less and chroma 4 or less and 2% or more redox depletions and/or redox concentrations as soft masses and/or pore linings."

Change 13: Page 19, Red Parent Material, an additional sentence is added as "The minimum thickness requirement is 5 cm. (2 in.) if the layer is the mineral surface layer."

Change 14: Page 19, Red Parent Material, User Notes, an additional sentence is added as "This indicator also occurs on "Red River" flood plains such as the Chattahoochee, Congaree, Red, and Tennessee Rivers."

The red parent material indicator and user notes would thus read as follows:

TF2. Red Parent Material. For testing in LRRs with red parent material. In parent material with a hue of 7.5YR or redder, a layer at least 10 cm (4 in.) thick with a matrix value 4 or less and chroma 4 or less and 2% or more redox depletions and/or redox concentrations as soft masses and/or pore linings. The layer is entirely within 30 cm (12 in.) of the soil surface. The minimum thickness requirement is 5 cm (2 in.) if the layer is the mineral surface layer.

Red Parent Material User Notes: This indicator was developed for use in areas of red parent material such as: Triassic/Jurassic sediments in the Connecticut River valley, Permian "red beds" in Kansas, clayey red till and associated lacustrine deposits around the Great Lakes, and Jurassic sediments associated with "hogbacks" on the eastern edge of the Rocky mountains. This indicator also occurs on "Red River" flood plains such as the Chattahoochee, Congaree, Red, and Tennessee Rivers. Redox features most noticeable in red materials include redox depletions and soft manganese masses that are black or dark reddish black.

Change 15: Page 25, Glossary, Mucky Modified Texture, second sentence is changed to Mucky modified mineral soil with 60 percent clay has between 12 and 18 percent organic carbon.

Change 16: Page 13, F1, Loamy Mucky Mineral, First sentence is changed to "For use in all LRRs except V, W, X, and Y and MLRA 1 of LRR A."

Change 17: The following test indicator is added:

TA2. Structureless Muck. For testing in MLRAs 141, 143, 144b, 145, and 146 of LRR R. Starting within 15 cm (6 in.) of the soils surface on concave positions or in depressions, a layer of muck 2 cm (0.75 in.) or more thick that has no soil structure.

Structureless Muck User Notes: Non-hydric muck horizons have low moisture content and are usually fluffy or have weak to moderate structure. Hydric muck horizons are usually wet and amorphous or, if dry, then hard and difficult to rewet.