LOCATION OGTNA                   AK

Established Series
Rev. MHC/JPM
05/2022

OGTNA SERIES

The Ogtna series consists of very deep, well drained soils formed in stratified sandy and silty alluvium over sand and gravel. Ogtna soils are on low stream terraces. Slopes range from 0 to 9 percent. Mean annual temperature is about 26 degrees F., and the average annual precipitation is about 16 inches.

TAXONOMIC CLASS: Coarse-loamy over sandy or sandy-skeletal, mixed, superactive Typic Humicryepts

TYPICAL PEDON: Ogtna loam - on a level slope under willow scrub 2850 feet elevation. (All colors are for moist soil)

Oi--6 to 2 inches; dark reddish gray (2.5YR 3/1) peat; consisting of fibrous moss, roots, and twigs; many very fine roots; clear smooth boundary. (3 to 5 inches thick)

Oa--2 to 0 inches; black (10YR 2/1) muck; consisting of decomposed moss, roots, and twigs; many very fine roots; clear smooth boundary. (0 to 3 inches thick)

A/Oa1--0 to 4 inches; dark brown (10YR 3/3) and 40 percent black (10YR 2/1) occurring in a stratified pattern; stratified sand through muck with a composite texture of mucky fine sandy loam; moderate medium subangular blocky structure; very friable, nonsticky and nonplastic; many very fine roots; strongly acid (pH 5.4); clear smooth boundary. (3 to 10 inches thick)

A/Oa2--4 to 13 inches; dark brown (10YR 3/3) and 25 percent black (10YR 2/1) occurring in a stratified pattern; stratified sand, fine sand, very fine sand, silt and muck with a composite texture of loam; moderate medium subangular blocky structure; very friable, nonsticky and nonplastic; many very fine roots; moderately acid (pH 6.0); abrupt smooth boundary. (4 to 12 inches thick)

2C--13 to 60 inches; variegated extremely gravelly coarse sand; single grain; loose, nonsticky and nonplastic; 65 percent gravel; moderately acid (pH 6.0).

TYPE LOCATION: Gulkana River Area, Alaska; about 25 miles southwest of Paxson; the SE1/4 of the NE1/4 of section 1, T.13N., R.5W., Copper River Meridian.

RANGE IN CHARACTERISTICS: MAST ranges from 32 to 35 degrees F. The upper part of the control section is stratified very fine sandy loam, fine sandy loam, loamy fine sand, silt loam and muck. The composite texture contains less than 18 percent clay and more than 15 percent fine sand or coarser. Depth to sand and gravel ranges from 12 to 22 inches. The lower part of the control section is sand or coarse sand with occasional strata of sandy loam and silt loam. Composite texture is sandy and coarse fragment content ranges from 40 to 75 percent rounded gravel and cobble. The soil is strongly acid to moderately acid solum and slightly acid to neutral in the 2C horizons.

The A/Oa horizons have moist value of 2 or 3; and moist chroma from 1 through 3. Texture includes stratified very fine sandy loam, fine sandy loam or silt loam with muck and mucky peat.

The 2C horizon is variegated Coarse fragment content ranges from 40 to 75 percent with 35 to 65 percent gravel and 0 to 20 percent cobble.

COMPETING SERIES: There are no competing series in the same family and the Grubstake series in the same subgroup. Grubstake soils have loamy-skeletal particle-size control sections.

GEOGRAPHIC SETTING: Ogtna soils formed in stratified loamy alluvium over sandy-skeletal alluvium on low stream terraces. The terraces are often dissected. Slopes range from 0 to 7 percent.

GEOGRAPHICALLY ASSOCIATED SOILS:

The climate is subarctic continental with long, cold winters and short, warm summers. Mean annual precipitation ranges from 8 to 17 inches, and the mean annual snowfall is 39 to 68 inches. Mean January temperature is minus 10 degrees F., mean July temperature is 56 degrees F., and the mean annual temperature ranges from 23 to 27 degrees F.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate in the upper part and rapid in the gravelly substratum. Runoff is slow.

USE AND VEGETATION: Most areas have native vegetation of willow scrub.

DISTRIBUTION AND EXTENT: Copper River Basin, Alaska. The series is of minor extent.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: WASILLA, ALASKA

SERIES ESTABLISHED: Gulkana River Area, Alaska. 1999.

REMARKS: Diagnostic features and horizons recognized in this pedon include: an umbric epipedon from 0 to 13 inches; coarse-loamy particle size from 0 to 13 inches and sandy skeletal particle size from 13 to 60 inches; cryic temperature regime. Formerly classified as Entic Cryumbrepts.

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National Cooperative Soil Survey
U.S.A.