LOCATION ISIDOR AK

Established Series
Rev: LAR/DMK/JPM
05/2022

ISIDOR SERIES

The Isidor series consists of shallow to compact glacial till, very poorly drained soils that formed in glacial till on moraines, drumlins, and backslopes and crests of hills. Slopes range from 0 to 40 percent. Mean annual temperature is about 45 degrees F., and the average annual precipitation is about 120 inches.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, shallow Placic Cryaquods

TYPICAL PEDON: Isidor silt loam - on a southeast facing, 15 percent hillslope at 200 feet elevation under conifer vegetation. (All colors are for moist soil)

Oe--9 to 0 inches; black (5YR 2.5/1) mucky peat; very friable, nonsticky and nonplastic; many fine, common medium and coarse roots; extremely acid (pH 4.0); clear smooth boundary. (4 to 9 inches thick)

E--0 to 4 inches; dark grayish brown (10YR 4/2) silt loam; weak fine subangular blocky structure; very friable, nonsticky and nonplastic; common fine and medium, and few coarse roots; 5 percent gravel; very strongly acid (pH 4.5); clear smooth boundary. (2 to 6 inches thick)

Bhs--4 to 10 inches; dark reddish brown (5YR 3/2) very gravelly sandy loam; weak fine subangular blocky structure; very friable, nonsticky and nonplastic; few fine and medium roots; 55 percent gravel; strongly acid (pH 5.5); abrupt smooth boundary. (4 to 11 inches thick)

Bsm/Bs--10 to 11 inches; 20 percent black (N 2/0) cemented iron and organic pan (about .2 inches thick); indurated; moderately acid (pH 5.8); 80 percent dark reddish brown (5YR 3/3) very gravelly sandy loam (about .8 inches thick); weak medium platy structure; friable, nonsticky and nonplastic; common large prominent very dusky red (2.5YR 2.5/2) and common medium distinct yellowish brown (10YR 5/8) mottles; 50 percent gravel; moderately acid (pH 6.0); abrupt smooth boundary. (1 to 2 inches thick)

Cd--11 to 60 inches; dark yellowish brown (10YR 4/4) extremely gravelly sandy loam; compact till; few medium distinct strong brown (7.5YR 5/8) and few fine faint grayish brown (10YR 5/2) mottles; massive; extremely firm; 75 percent gravel; very strongly acid (pH 4.5).

TYPE LOCATION: Ketchikan Soil Survey Area, Alaska; about 2000 feet south of Pt. Santa Gertrudis, Lulu Island; SW 1/4, NW 1/4, Section , T.73 S., R.79E., Copper River Meridian.

RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 38 to 42 degrees F. The histic epipedon ranges from 8 to 15 inches in thickness and includes part of the E horizon in some pedons. The thickness of the solum ranges from 10 to 14 inches. The depth to the compact till layer ranges from 10 to 14 inches. The rock fragment content in the particle size control section ranges from 40 to 60 percent and is dominantly gravel size. Reaction throughout the mineral layers is medium to very strongly acid. Coarse fragments are predominantly fine gravel in all horizons. The average summer soil temperature at the compact till surface is about 46 degrees F.

Colors in the Oe horizon range in hue from 5YR to 10YR with moist values of 2 or 3, and moist chromas from 0 to 2. The E horizon has hue of 10YR or 7.5YR; value moist ranges from 3 to 6; and the chroma moist is 2 or 3. The texture is commonly silt loam or mucky silt loam, but ranges to include sandy loam. Coarse fragment content is less than 35 percent and is dominantly gravel size.

The Bhs horizon has hue from 10YR through 5YR; value moist from 2 through 4; and chroma moist from 0 through 2. Texture is commonly sandy loam but ranges to include very fine sandy loam. Coarse fragment content ranges from 40 to 60 percent and is dominantly gravel.

The Bsm layer has hue from 2.5Y to 2.5YR, value moist of 2 or 2.5, and chroma moist of 0 or 1. The horizon is indurated with extremely firm consistence.

The Bs layer has hue from 2.5YR through 10R, value moist of 3 or 4, and chroma moist from 4 through 6.

The Cd horizon has hue ranging from 2.5Y through 10YR; value moist from 3 through 5; and chroma moist from 2 through 4. Mottles have hue of 7.5YR or 10YR, value moist of 4 or 5, and chroma moist from 2 through 8. Coarse fragment content ranges from 50 to 80 percent and is dominantly gravel size.

COMPETING SERIES: This is the inactive Shinaku series which is poorly defined. Also the Wadleigh series which lacks a placic layer.

GEOGRAPHIC SETTING: The Isidor soils are on moraines, drumlins, and hillslopes. The parent material is glacial till of mixed mineralogy. The climate is humid maritime with mean annual precipitation of 120 inches. The mean annual air temperature is 45 degrees F., and the average summer air temperature is 55 degrees F. The slope gradient is commonly 25 to 35 percent but ranges from 0 to 40 percent. Elevation ranges from 100 to 400 feet.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Kaikli, Kina, Maybeso, Mitkof, St. Nicholas, and Wadleigh soils. Kaikli, Kina, and Maybeso soils are organic soils in depressional areas. Mitkof and Wadleigh soils lack a placic horizon and are on hillslopes. St. Nicholas soils have a lithic contact within 20 inches of the surface and are on hillslopes.

DRAINAGE AND PERMEABILITY: Poorly drained. Moderate permeability above the placic horizon. Very slowly permeable in the placic layer and the compact till layer. Runoff is slow under native vegetation, however, if the surface is disturbed, the runoff is medium to rapid.

USE AND VEGETATION: The Isidor soils are used for wildlife habitat, recreation, watershed protection, and timber production. The overstory vegetation consists mainly of Alaska yellow cedar and lodgepole pine, with some western red cedar, western hemlock, and mountain hemlock included. The understory vegetation is dominantly Alaska yellow cedar, blueberries, mountain hemlock, and rusty menziesia. The ground cover is mainly salal, skunk cabbage, deer fern, bunchberry dogwood, and feather moss.

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

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

SERIES ESTABLISHED: Ketchikan Area, Alaska. 1994.

REMARKS: Diagnostic horizons and features recognized in this pedon include: an albic horizon from 0 to 4 inches; a spodic horizon from 4 to 10 inches; a histic epipedon from 9 to 0 inches; a thin placic layer; loamy-skeletal material from 0 to 10 inches; a cryic temperature regime.

National Cooperative Soil Survey
U.S.A.