LOCATION GUNNUK                  AK

Established Series
Rev. SR-EJK-JPM
05/2022

GUNNUK SERIES

The Gunnuk series consists of very deep, moderately well drained soils formed in silty glacio-marine or glacio-lacustrine sediments. Gunnuk soils occur on uplifted marine terraces or on glacial lake plains. Slopes range from 5 to 60 percent. Mean annual air temperature is about 45 F., and mean annual precipitation is about 90 inches.

TAXONOMIC CLASS: Fine-silty, mixed, semiactive Typic Haplocryods

TYPICAL PEDON: Gunnuk silt loam - on a south facing slope of 50 percent under spruce-hemlock forest at 250 feet elevation. (All colors are for moist soil).

Oa--6 to 0 inches; very dark grayish brown (10YR 3/2) muck; 20 percent fiber, 5 percent rubbed; primarily decomposed forest litter; many very fine and medium roots; extremely acid (pH 4.0 Truog); abrupt smooth boundary. (5 to 12 inches thick).

E--0 to 1 inch; gray (10YR 5/1) silt loam; weak fine platy structure; very friable, nonsticky and slightly plastic; many very fine and fine, and common medium roots; extremely acid (pH 4.2 Truog); abrupt wavy boundary. (1 to 3 inches thick).

Bh--1 to 3 inches; black (5YR 2.5/1) silt loam; moderate fine subangular blocky structure; very friable, nonsticky and slightly plastic; many fine, and common medium and coarse roots; very strongly acid (pH 4.5 Truog); abrupt wavy boundary. (1 to 4 inches thick).

Bs1--3 to 5 inches; dark brown (7.5YR 3/4) silt loam; moderate fine and very fine subangular blocky structure; friable, nonsticky and slightly plastic; common fine, and few medium roots; very strongly acid (pH 5.0 Truog); abrupt wavy boundary. (1 to 8 inches thick).

Bs2--5 to 9 inches; strong brown (7.5YR 4/6) silt loam; moderate fine and very fine subangular blocky structure; friable, nonsticky and slightly plastic; common fine, and few medium roots; strongly acid (pH 5.2 Truog); abrupt wavy boundary. (2 to 10 inches thick).

Bw--9 to 17 inches; light olive brown (2.5Y 5/4) silt loam; few fine faint dark yellowish brown (10YR 4/4) mottles; moderate medium and fine subangular blocky structure; firm, nonsticky and slightly plastic; few fine roots; strongly acid; (pH 5.5 Truog); gradual wavy boundary. (0 to 12 inches thick).

BC--17 to 34 inches; olive gray (5Y 5/2) silty clay loam; common medium prominent yellowish red (5YR 5/6) mottles; weak medium subangular blocky structure; firm, slightly sticky and slightly plastic; slightly acid (pH 6.2 Truog); gradual wavy boundary. (0 to 17 inches thick).

C--34 to 60 inches; olive (5Y 5/3) silty clay; common medium prominent yellowish red (5YR 4/6) mottles; massive; sticky and slightly plastic; slightly acid (pH 6.4 Truog).

TYPE LOCATION: Kupreanof Island, Alaska. 7 miles south east of Kake in SE 1/4, Section 18, T.57N., R.74E., Copper River Meridian.

RANGE IN CHARACTERISTICS: MAST ranges from 38 to 42 degrees F. Thickness of the solum ranges from 12 to 35 inches. The 10 to 40 inch control section has a weighted average of 18 to 35 percent clay with less than 15 percent fine sand or coarser. Texture is typically silt loam or silty clay loam but the range includes some subhorizons of very fine sandy loam, silty clay or clay loam. Coarse fragment content ranges from 0 to 15 percent in some pedons. The lower solum and C horizons are mottled. Reaction ranges from extremely acid to strongly acid in the upper solum and is slightly acid or neutral in the BC and C horizons.

The E horizon has hue of 10YR or 2.5Y, value of 3 to 6 and chroma of 1 or 2. Texture is silt loam, loam, or silty clay loam.

The Bh horizon has hue of 5YR, 7.5YR or 10YR, value of 2 or 3 and chroma of 1 or 2. Texture is silt loam or silty clay loam.

The Bs horizons have hue of 5YR, 7.5YR, or 10YR, value of 3 to 5 and chroma from 3 to 6. Texture is silt loam or silty clay loam.

The Bw horizon, when present, has hue of 10YR, 2.5Y or 5Y, value of 4 or 5 and chroma from 1 to 4. Texture is silt loam, silty clay loam or silty clay.

The C horizon has hue of 2.5Y or 5Y, value of 4 or 5 and chroma from 1 to 3. Texture is typically silt loam, silty clay loam or silty clay but often contains thin strata of very fine sandy loam, loam or clay loam.

COMPETING SERIES: This is the Sloduc series. Sloduc soils are mottled and contain iron and manganese concretions in the upper part of the spodic horizons.

GEOGRAPHIC SETTING: Gunnuk soils occur on uplifted glacial marine terraces and old glacial lake plains. Slopes range from 5 to 60 percent. Mean annual temperature is about 45 F., and mean annual precipitation is about 90 inches. Elevation is typically less than 300 feet but ranges from sea level to 900 feet.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Kupreanof, Maybeso and Wadleigh soils. Kupreanof soils are on colluvial footslopes and mountain sideslopes and have coarser textures. Maybeso soils are on concave slopes and are very poorly drained. Wadleigh soils are poorly drained soils on glacial moraines.

DRAINAGE AND PERMEABILITY: Moderately well drained. A perched water table is at depths of 10 to 40 inches for brief periods during the growing season. Permeability is moderately slow in the solum and very slow in the C horizon. Runoff is slow to medium under native vegetation, however if the surface organic horizon is disturbed the runoff is rapid.

USE AND VEGETATION: The Gunnuk soils are used for timber production, wildlife habitat and recreation. The native vegetation is a western hemlock-Sitka spruce forest with an understory of blueberry, rusty menziesia, bunchberry, five-leaf bramble and shield fern.

DISTRIBUTION AND EXTENT: Southeast Alaska. The series is not extensive.

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

SERIES ESTABLISHED: Stikine Area, Alaska, 1993.

REMARKS: Diagnostic horizons and features recognized in this soil are: a. spodic horizon from 1 to 9 inches; assumed cryic temperature regime; values less than 4 in the upper spodic horizons with mottles present immediately below the spodic horizon; weighted average particle size of fine-silty material from 10 to 40 inches.

The classification has been changed from medial over clayey, mixed, Humic Cryorthods. The type location has also been changed from the 1969 site because of insufficient documentation.

ADDITIONAL DATA: Lab data are available at the National Soil Survey Lab. NSSL Pedon Number: 86P0165

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National Cooperative Soil Survey
U.S.A.