LOCATION SLODUC AK

Established Series
Rev. EJK-JPM
02/2022

SLODUC SERIES

The Sloduc series consists of very deep, poorly drained soils formed in silty glacio-marine or glacio-lacustrine sediments. Sloduc 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 degrees F., and mean annual precipitation is about 90 inches.

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

TYPICAL PEDON: Sloduc silt loam - on a north facing slope of 1 percent, under forest vegetation. (All colors are for moist soil).

0i--10 to 7 inches; dark reddish brown (5YR 3/2) peat; 90 percent fiber, 60 percent rubbed; primarily moss and forest litter; many fine and medium roots; extremely acid (pH 4.0 Truog); clear wavy boundary. (0 to 4 inches thick)

0a--7 to 0 inches; dark reddish brown (5YR 2.5/2) muck; 20 percent fiber, 10 percent rubbed; primarily moss and forest litter; common fine, medium and coarse roots; extremely acid (pH 4.0 Truog); abrupt smooth boundary. (5 to 12 inches thick)

E--0 to 3 inches; gray (5YR 5/1) and dark reddish brown (5YR 3/2) silt loam; weak medium subangular blocky structure; very friable, nonsticky and nonplastic; common fine and few medium roots; very strongly acid (pH 4.5 Truog); clear wavy boundary. (1 to 4 inches thick)

Bh--3 to 6 inches; black (5YR 2.5/1) silt loam; moderate fine subangular blocky structure; very friable, slightly sticky and slightly plastic; few fine roots; common fine rounded concretions; very strongly acid (pH 5.0 Truog); clear wavy boundary. (1 to 4 inches thick)

Bhs--6 to 11 inches; dark grayish brown (10YR 4/2) silt loam; moderate medium and fine subangular blocky structures; friable, slightly sticky and slightly plastic; common dark reddish brown (5YR 2.5/2) coatings on peds; few fine rounded black (5YR 2.5/1) concretions; strongly acid (pH 5.3 Truog); clear wavy boundary. (4 to 7 inches thick)

BC1--11 to 16 inches; olive gray (5Y 5/2) silt loam; moderate medium subangular blocky structure; friable, slightly sticky and slightly plastic; common reddish gray (5YR 5/2) coatings in pores; common reddish brown (5YR 4/4) coatings on faces of peds; strongly acid (pH 5.5 Truog); gradual wavy boundary. (4 to 7 inches thick)

BC2--16 to 27 inches; gray (5Y 5/1) and light olive gray (5Y 6/2) silty clay loam; weak medium subangular blocky structure; firm, slightly sticky and slightly plastic; few reddish gray (5YR 5/2) coatings in pores; strongly acid (pH 5.5 Truog); gradual wavy boundary. (5 to 12 inches thick)

C--27 to 60 inches; olive gray (5Y 5/2) silty clay loam; massive; slightly sticky and slightly plastic; slightly acid (pH 6.5 Truog).

TYPE LOCATION: Kupreanof Island, Alaska, about 7 miles southeast of Kake; SE1/4, Section 18, T.57N., R.74E., Copper River Meridian.

RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 38 to 42 degrees F. Thickness of solum ranges from 10 to 27 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. The upper part of the solum is mottled and contains iron and/or manganese concretions. Reaction is extremely acid to strongly acid in the solum and slightly acid or neutral in the C horizon.

The E horizon has hue of 5YR, 7.5YR, 10YR, 2.5Y or 5Y, value from 3 to 6 and chroma of 1 or 2. Texture is silt 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 Bhs horizon has hue of 5YR, 7.5YR or 10YR, value of 3 or 4, and chroma of 1 or 2. Texture is silt loam or silty clay loam.

The C horizon has hue of 2.5Y or 5Y, value from 4 to 6 and chroma of 1 or 2. Texture is typically silt loam or silty clay loam but often has thin strata of very fine sandy loam, silty clay or clay loam.

COMPETING SERIES: This is the Gunnuk series. Gunnuk soils do not have mottles or concretions in the upper part of the spodic horizon.

GEOGRAPHIC SETTING: Sloduc soils occur on uplifted glacial marine terraces and on old glacial lake plains. Slopes range from 5 to 60 percent. Mean annual temperature is about 45 degrees 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: There are the Maybeso and Wadleigh soils. Maybeso soils are on concave slopes and are very poorly drained. Wadleigh soils are on glacial moraines and formed in glacial till.

DRAINAGE AND PERMEABILITY: Poorly drained. A perched water table is present at depths ranging from 0 to 20 inches during most of the year. Permeability is moderately slow in the solum and very slow in the C horizons. Runoff is slow under native vegetation, however, if the surface organic horizon is disturbed the runoff is medium to rapid.

USE AND VEGETATION: The Sloduc soils are used for timber production, wildlife habitat, and recreation. The native vegetation is primarily western hemlock with some Alaska yellow cedar, and Sitka spruce. Understory is dominantly blueberry, rusty menziesia, five-leaf bramble and skunk cabbage.

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: an spodic horizon from 3 to 16 inches; assumed cryic temperature regime; iron and/or manganese mottles and concretions throughout the spodic horizons; weighted average particle size of fine-silty material from 10 to 40 inches.

ADDITIONAL DATA: Lab samples are available at the National Soil Survey Lab. NSSL Pedon Number: 86P0164

National Cooperative Soil Survey
U.S.A.