LOCATION SITKA                   AK

Established Series
Rev. CSC/JMD/JPM
02/2022

SITKA SERIES

The Sitka series consists of very deep, well drained soils formed in volcanic ash on mountainslopes and hillslopes. Slopes range from 35 to 75 percent. Mean annual precipitation is in excess of 60 inches and the mean annual temperature is about 46 degrees F.

TAXONOMIC CLASS: Medial, amorphic Andic Humicryods

TYPICAL PEDON: Sitka fine sandy loam - on a east facing slope of 70 percent at 1000 feet elevation under conifer forest vegetation. (All colors are for moist soil, all textures are apparent field textures)

Oi-- 3 to 2 inches; forest litter and living mosses; many very fine, fine and few medium roots; abrupt smooth boundary. (1 to 4 inches thick).

Oa-- 2 to 0 inches; muck; many very fine, fine and few medium roots; extremely acid (pH 4.0); abrupt wavy boundary. (1 to 4 inches thick)

E-- 0 to 2 inches; dark grayish brown (10YR 4/2) fine sandy loam; weak fine subangular blocky structure; friable; few very fine and fine, common medium, and few coarse roots; very strongly acid (pH 4.5); abrupt wavy boundary. (1 to 2 inches thick)

Bh-- 2 to 3 inches; black (5YR 2.5/1) mucky very fine sandy loam; weak fine subangular blocky structure; friable; strongly smeary; few very fine and fine, common medium and few coarse roots; very strongly acid (pH 4.5); abrupt wavy boundary. (1 to 8 inches thick)

Bhs1-- 3 to 7 inches; dark reddish brown (5YR 2.5/2) and (5YR 3/3) very fine sandy loam; weak fine subangular blocky structure; very friable; strongly smeary; few fine, many medium and few coarse roots; strongly acid (pH 5.5); clear wavy boundary. (0 to 6 inches thick)

Bhs2-- 7 to 13 inches; dark reddish brown (5YR 3/3) fine sandy loam; weak medium subangular blocky structure; friable; strongly smeary; few medium and coarse roots; strongly acid (pH 5.5); clear wavy boundary. (0 to 6 inches thick)

BC-- 13 to 31 inches; strong brown (7.5YR 4/6) gravelly very fine sandy loam; weak medium subangular blocky structure; friable; strongly smeary; 20 percent gravel size pumice; few medium and coarse roots; moderately acid (pH 6.0); clear wavy boundary. (6 to 35 inches thick)

C-- 31 to 60 inches; strong brown (7.5YR 4/6) very fine sandy loam; massive; friable; slightly acid (pH 6.5).

TYPE LOCATION: Krestof Island, Chatham Area Alaska; SE 1/4, SE 1/4, Sec. 22, T.54S., R.62E., Copper River Meridian.

RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 38 to 42 degrees F. The mean summer soil temperature is about 45 degrees F. Thickness of the solum ranges from 14 to 50 inches. Phosphorous retention is greater than 85 percent. Bulk density throughout the soil is less than 0.90 g/cc. Moist 15 bar water is between 30 and 100 percent. Reaction increases with depth, ranging from extremely acid to slightly acid. The coarse fragment content ranges from 0 to 20 percent gravel size pumice.

The E horizon has hue from 5YR to 10YR, value moist of 4 or 5 and chroma moist of 1 or 2. Texture is commonly fine sandy loam but ranges to include silt loam, loam or very fine sandy loam. The Bh horizon has hue of 2.5YR or 5YR, and chroma moist of 0 or 1. Texture is dominantly very fine sandy loam but ranges to include sandy loam, silt loam, or loam, often with substantial organic carbon content.

The Bhs horizon has hue of 2.5YR or 5YR, value and chroma moist of 2 or 3. Texture is dominantly very fine sandy loam but ranges to include fine sandy loam, sandy loam, or silt loam. This horizon may be absent in some pedons.

A Bs horizon is present in some pedons. Hue is 5YR or 7.5YR, value moist is 3 or 4, and chroma moist ranges from 3 to 8. Texture is dominantly very fine sandy loam but ranges to include fine sandy loam, sandy loam or silt loam. Coarse fragment content ranges from 0 to 10 percent gravel size pumice.

The BC horizon has hue from 5YR to 10YR, value moist of 3 or 4, and chroma moist from 2 to 6. Texture is dominantly very fine sandy loam but ranges to include fine sandy loam, sandy loam or silt loam. Coarse fragment content ranges from 0 to 20 percent gravel size pumice.

The C horizon is composed of several strata of ash which vary in texture, color, percent course fragments and consistence. Hue ranges from 5YR to 2.5Y, value moist from 2 to 5 and chroma moist from 1 to 8. Texture ranges to include very fine sandy loam, fine sandy loam, sandy loam and silt loam. Coarse fragment content ranges from 0 to 15 percent gravel size pumice.

COMPETING SERIES: There are no competing series in the same family.

GEOGRAPHIC SETTING: The Sitka soils are on mountainslopes and hillslopes and formed in volcanic ash. The climate is humid maritime with a mean annual precipitation range of 60 to 220 inches. The mean annual temperature is about 46 degrees F. and the mean summer temperature is about 57 degrees F. Elevation ranges from 0 to 3000 feet.

GEOGRAPHICALLY ASSOCIATED SOILS: These include the McGilvery, Sukoi and Verstovia soils on similar landforms. McGilvery soils are organic and less than 10 inches deep to bedrock. Sukoi soils are poorly drained and are in wet depressions. Verstovia soils are less than 20 inches deep to bedrock.

DRAINAGE AND PERMEABILITY: Well drained. Very slow runoff. Moderate permeability.

USE AND VEGETATION: The Sitka soils are used for timber production, watershed protection, wildlife habitat and recreation. The overstory vegetation is dominantly western hemlock. The under story vegetation is dominantly blueberry, wood fern and mosses.

DISTRIBUTION AND EXTENT: Southeast Alaska. The series is of moderate extent.

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

SERIES ESTABLISHED: Chatham Area, Tongass National Forest, Alaska, 1992.

REMARKS: Diagnostic horizons and features recognized in this soil are: Andic properties from 0 to 60 inches; a cryic temperature regime; an albic horizon from 0 to 2 inches; a spodic horizon from 2 to 13 inches; assumed moist 15 bar water between 30 and 100 percent.

Laboratory data on andic properties is not available for this soil. Laboratory data was used from the Sukoi series (NSSL S87AK-220-010) which is an associated soil with similar morphology.

ADDITIONAL DATA: Limited laboratory data is available for this soil: University of Idaho Numbers 83-AK-0353 and 83-AK-0357.

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National Cooperative Soil Survey
U.S.A.