Established Series
Rev. JPM


The Wasilla series consists of very deep, poorly drained soils formed in silty alluvium on floodplains and alluvial terraces. Slopes range from 0 to 3 percent. The mean annual temperature is about 34 degrees F., and the average annual precipitation is about 25 inches

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, acid Humic Cryaquepts

TYPICAL PEDON: Wasilla silt loam on a 1 percent slope under native grass. (All colors are for moist soils).

0e--4 inches to 0; very dark brown (10YR 2/2) mat of moderately decomposed moss and sedge; many fine and medium roots; abrupt smooth boundary. (2 to 7 inches thick)

A1--0 to 2 inches; dark brown (10YR 3/3) silt loam; weak fine granular structure; friable, nonsticky and nonplastic; many fine and medium roots; very strongly acid; abrupt smooth boundary. (1 to 5 inches thick)

A2g--2 to 10 inches; very dark grayish brown (10YR 3/2) silt loam; moderate fine granular structure; friable; nonsticky and nonplastic; common fine distinct yellowish red (5YR 5/6) mottles; common fine and medium roots; very strongly acid; abrupt smooth boundary. (0 to 8 inches thick)

C1g--10 to 26 inches; dark gray (2.5Y 4/0) silt loam; massive; friable, sticky and slightly plastic, common fine prominent strong brown (7.5YR 5/6) mottles; few fine roots; very strongly acid; clear wavy boundary. (5 to 16 inches thick)

C2g--26 to 60 inches; light gray (2.5Y 7/2) silt loam stratified with silty clay loam and fine sandy loam; massive, firm, sticky and plastic; common fine distinct yellowish brown (10YR 5/8) mottles; very strongly acid.

TYPE LOCATION: Yentna Area, Alaska; SE 1/4, SW 1/4, section 23, T.21N., R.9W., Seward Meridian.

RANGE IN CHARACTERISTICS: Thickness of the umbric epipedon ranges from 10 to 13 inches. Mottling and matrix chromas of 2 or less occur within 20 inches of the surface. The control section consists of strata of silt loam, fine sandy loam, and silty clay loam. Clay content ranges from 18 to 35 percent with greater than 15 percent fine sand or coarser. Gravelly alluvium or glacial till may occur below 40 inches. Reaction throughout the profile is very strongly or strongly acid.

The A horizon has hue of 7.5YR, 10YR, or 2.5Y; value moist of 2 or 3; and chroma moist from 1 through 3. Content of coarse fragments is less than 15 percent.

The C horizons have hue of 10YR, 2.5Y, or 5Y; value moist from 4 through 7; and chroma moist from 0 through 2.

COMPETING SERIES: These are the Clam Gulch and Melton series in the same subgroup. Clam Gulch soils contain less than 15 percent fine or coarser sand. Melton soils contain sandy or sandy skeletal material in the lower part of the control section.

GEOGRAPHIC SETTING: Wasilla soils are on floodplains and alluvial terraces. Slopes range from 0 to 3 percent. The mean annual temperature ranges from 32 to 36 degrees F., and the average annual precipitation ranges from 17 to 32 inches.

DRAINAGE AND PERMEABILITY: Poorly drained. Permeability is moderately slow. Runoff is slow. Subject to flooding.

USE AND VEGETATION: The native vegetation consists of alder, willows, grass, and scattered black spruce, paper birch, and cottonwood. Used for wildlife habitat.

DISTRIBUTION AND EXTENT: South-central Alaska. The series is of moderate extent.


SERIES ESTABLISHED: Matanuska Valley Area, Alaska, 1966.

REMARKS: Diagnostic horizons and features recognized in this profile include: An umbric epipedon from 0 to 10 inches; mottling and matrix chroma of 2 or less from 2 to 60 inches; a cryic temperature regime; pH is less than 5.5 (H2O,1:1) throughout the control section; clay content is between 18 and 35 percent from 10 to 40 inches.