LOCATION NAKOCHNA                AK

Established Series
Rev. KMO/DM
05/2022

NAKOCHNA SERIES

The Nakochna series consists of shallow, well drained soils formed in a mantle of ash influenced loess overlying granite bedrock. Nakochna soils are on mountain ridges and side slopes. Slopes range from 2 to 85 percent. The mean annual temperature is about 32 degrees F. The average annual precipitation is about 26 inches.

TAXONOMIC CLASS: Medial, amorphic Lithic Humicryods

TYPICAL PEDON: Nakochna silt loam - on a 3 percent slope under alpine tundra vegetation. (All colors are for moist soil)

Oi--0 to 2 inches; slightly decomposed plant material from alpine tundra vegetation; very strongly acid (pH 4.6) abrupt smooth boundary. (1 to 4 inches thick)

A--2 to 4 inches; very dark brown (10YR 2/2) silt loam; weak fine subangular blocky structure; very friable; many fine roots; very strongly acid; abrupt smooth boundary. (0 to 3 inches thick)

E--4 to 5 inches; dark grayish brown (10YR 4/2) silt loam; weak fine subangular blocky structure; very friable, nonsticky and nonplastic; many fine roots; very strongly acid; abrupt broken boundary. (1 to 2 inches thick)

Bhs1--5 to 6 inches; dark reddish brown (5YR 2.5/2) silt loam; weak fine granular structure; very friable, smeary, nonsticky and nonplastic; pockets of dark grayish brown (10YR 4/2) and very dusky red (2.5YR 2.5/2) frost churned material; very strongly acid; abrupt broken boundary.

Bhs2--6 to 8 inches; very dusky red (2.5YR 2.5/2) silt loam; weak fine granular structure; very friable, smeary, nonsticky and nonplastic; pockets of dark reddish brown (5YR 2.5/2 and 5YR 3/4) frost churned material; very strongly acid; gradual broken boundary. (Combined Bsh horizons: 3 to 9 inches thick)

Bs--8 to 14 inches; dark reddish brown (5YR 3/4) silt loam; weak fine granular structure; very friable, slightly smeary, nonsticky and nonplastic; pockets of very dusky red (2.5YR 2.5/2) and brown (10YR 4/3) frost churned material; very strongly acid; gradual broken boundary. (0 to 6 inches thick)

C--14 to 19 inches; brown (10YR 4/3) gravelly silt loam; massive; friable, nonsticky and nonplastic; 25 percent gravel; very strongly acid; abrupt wavy boundary. (0 to 7 inches thick)

2R--19 inches; hard granite bedrock.

TYPE LOCATION: Yentna Area, Alaska; in the NE 1/4 of the NW 1/4 of section 2, T.19N., R.13W., Seward Meridian.

RANGE IN CHARACTERISTICS: Depth to bedrock ranges from 14 to 20 inches. The solum ranges in thickness from 12 to 20 inches. Buried horizons are present in some pedons. The exchange complex of the solum is dominated by amorphous material. The upper 6 inches of the spodic horizons have more than 6 percent organic carbon. Frost action has churned and mixed the horizons. Coarse fragment content increases with depth in the profile. Total coarse fragment content in the control section is less than 35 percent with 5 to 10 percent cobbles and 5 to 25 percent gravel. Thin ash layers (1/4 to 1 inch thick) occur in the upper part of some pedons. Reaction throughout the profile is very strongly or strongly acid.

The A horizon has hue of 5YR to 10YR value of 2 to 4, and chroma of 1 to 3. Texture is silt loam or very fine sandy loam. This horizon is not evident in many horizons due to frost churning.

The E horizon has hue of 5YR to 10YR value of 4 to 6, and chroma of 1 or 2. Texture is silt loam or very fine sandy loam.

The Bhs horizons have hue of 2.5YR to 10YR value of 2 or 3, and chroma of 1 or 2. Texture is silt loam or very fine sandy loam.

The Bs horizon has hue from 2.5YR to 7.5YR value from 3 to 5, and chroma 3 to 6. Texture is silt loam or very fine sandy loam.

C Texture is silt loam or gravelly silt loam.

COMPETING SERIES: This is the Verstovia series. Verstovia soils are not churned by frost.

GEOGRAPHIC SETTING: Nakochna soils are on mountain ridges and side slopes. Slopes range from 2 to 80 percent. The soils formed in a mantle of ash influenced loess overlying granite bedrock. The surface is characterized by hummocks resulting from frost action. The mean annual temperature ranges from 30 to 34 degrees F. The average annual precipitation ranges from 20 to 50 inches.

GEOGRAPHICALLY ASSOCIATED SOILS: These include the Chuit, Kliskon, and Puntilla soils, all on similar landforms. Chuit, Kliskon, and Puntilla soils have a firm glacial till substratum to 60 inches or more.

DRAINAGE AND PERMEABILITY: Well drained. Low to very high runoff. Moderate permeability.

USE AND VEGETATION: The native vegetation is characteristic of alpine tundra mainly ericaceous shrubs, dwarf birch, prostrate willows, mosses, and lichens. Use is restricted by the short growing season.

DISTRIBUTION AND EXTENT: South Central Alaska Mountains. The series is of moderate extent.

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

SERIES ESTABLISHED: Yentna Area, Alaska, 1986.

REMARKS: Diagnostic horizons and features recognized in this pedon include: albic horizon from 4 to 5 inches; spodic horizons from 5 to 15 inches; cryic temperature regime; more than 6 percent organic carbon in the upper 4 inches of the spodic horizon; a lithic contact at 19 inches; an exchange complex dominated by amorphous material.

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National Cooperative Soil Survey
U.S.A.