LOCATION TOLSONA AK

Established Series
Rev. MHC/JPM
02/2022

TOLSONA SERIES

The Tolsona series consists of very poorly and poorly drained soils formed in a thin mantle of eolian silt overlying glacial till and associated outwash on gently sloping glacial till plains and in depressions between drumlins. Permafrost occurs at a depth between 14 and 26 inches below the mineral surface. Slopes range from 0 to 20 percent. Mean annual temperature is about 26 degrees F. and mean annual precipitation is about 12 inches.

TAXONOMIC CLASS:

TYPICAL PEDON: Tolsona peat - on a 5 percent slope under black spruce forest at 1700 feet elevation. When described the soil was wet.

Oi--8 to 4 inches; dark reddish brown (5YR 2.5/2) peat consisting of slightly decomposed moss, twigs and root fibers; clear smooth boundary. (3 to 6 inches thick)

Oe--4 inches to 0; black (10YR 2/2) mucky peat; partially decomposed moss, twigs, and root fibers; gradual smooth boundary. (3 to 7 inches thick)

A--0 to 3 inches; dark brown (10YR 3/3) and black (10YR 2/2) mucky silt loam; weak medium subangular blocky structure; very friable, nonsticky and nonplastic; common very fine and fine roots; neutral (pH 7.0); abrupt wavy boundary. (1 to 8 inches thick)

2C1-- 3 to 17 inches; dark grayish brown (2.5Y 4/2) gravelly loam; massive; very friable, slightly sticky and slightly plastic; common medium distinct dark yellowish brown (10YR 4/4) mottles; 20 percent gravel and 5 percent cobble; few very fine and fine roots; neutral (pH 7.2); gradual irregular boundary. (2 to 19 inches thick)

2C2--17 to 24 inches; olive gray (5Y 5/2) gravelly sandy loam; massive; very friable, nonsticky and nonplastic; 20 percent gravel; mildly alkaline (pH 7.4); abrupt smooth boundary. (0 to 10 inches thick)

2Cf--24 to 34 inches; olive gray (5Y 5/2) gravelly sandy loam; common medium distinct olive gray (2.5Y 4/4) mottles; frozen on August 10, 1984.

TYPE LOCATION: Copper River Area, Alaska; approximately 10 miles northeast of Chitina; about 700 feet north and 300 feet west of the SE corner of section 21, T. 3S., R. 7E., Copper River Meridian.

RANGE IN CHARACTERISTICS: The mean annual soil temperature is less than 32 degrees F. The mat of organic material consists of fibrous moss over partially decomposed moss, twigs, and root fibers 8 to 13 inches thick. Depth to permafrost ranges from 14 to 26 inches below the mineral surface 2 months after the summer solstice. The loess mantle ranges from less than 1 to 8 inches thick. The particle size control section has less than 18 percent clay and more than 15 percent fine sands or coarser. Coarse fragment content in the control section ranges from 0 to 25 percent. The soil is medium acid or slightly acid in the organic mat and slightly acid to mildly alkaline in the mineral soil.

The A horizon has hue of 7.5YR or 10YR; moist value of 2, 3, or 4; and moist chroma of 1, 2, or 3. Texture commonly is mucky silt loam but ranges to include silt loam or very fine sandy loam. Coarse fragment content ranges from 0 to 5 percent and is dominantly subangular gravel and cobble.

The 2C horizons have hue of 7.5YR, 10YR or 2.5Y; moist value of 2, 3, 4 or 5; and moist chroma of 1, 2, or 3. Textures include loam, fine sandy loam and sandy loam. Coarse fragment content ranges from 5 to 30 percent cobble and gravel. A lag concentration of coarse fragments is often present at the surface of the horizon. This horizon is often broken and discontinuous with pockets of A and C horizons intermixed. Mottles with moist value and chroma of 3 or 4 are common. The 2Cf horizon has hue of 10YR, 2.5Y, or 5Y; moist value of 3, 4, or 5; and moist chroma of 1 or 2. Textures include loam, fine sandy loam, or sandy loam. Coarse fragment content ranges from 5 to 30 percent cobble and gravel.

COMPETING SERIES: These are the Copper River, Deborah(T), Kuslina, Mendeltna, Saulich, and Umiat(T) series. Copper River and Deborah series have silty textures with less than 15 percent fine sand or coarser. Kuslina soils are stratified silt and sand. Mendeltna soils have more than 18 percent clay. Saulich soils have substantial mica content. Umiat soils have weathered bedrock within the control section.

GEOGRAPHIC SETTING: Tolsona soils formed in a thin eolian silt mantle overlying glacial till and associated outwash on gently sloping glacial till sheets and in depressional areas between drumlins. Slopes are 0 to 20 percent.

The climate is subarctic continental with long, cold winters and short, warm summers. Mean annual precipitation ranges from 8 to 17 inches and the mean annual snowfall ranges from 39 to 68 inches. Mean January temperature is minus 10 degrees F., mean July temperature is 56 degrees F., and the mean annual temperature ranges from 23 to 27 degrees F.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Klawasi and Tsana(T) soils. Klawasi soils are on lacustrine terraces and have less than 10 inches of silt loam over clayey substratums. Tsana soils are on similar landforms and are the thawed counterparts of the Tolsona soils. Due to disturbance of the organic mat, the permafrost table and water table have dropped below the control section in the Tsana soils.

DRAINAGE AND PERMEABILITY: Very poorly and poorly drained. Runoff is slow. Permeability is moderate above the permafrost. Altered drainage occurs where the insulating organic mat is destroyed by fire or clearing. Loss of the organic mat results in lowering of the permafrost level with subsequent lowering of the water table. Texture and permeability of the thawed substratum is similar to that of the overlying layers.

USE AND VEGETATION: Most areas of Tolsona soils have native vegetation of black spruce, white spruce, and tall willow. The successional state of vegetation in a given area is closely related to the fire history. This soil is used primarily for wildlife habitat.

DISTRIBUTION AND EXTENT: Copper River Basin. The series is extensive.

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

SERIES ESTABLISHED: Copper River Area, Alaska. 1986.

REMARKS: Diagnostic horizons and features recognized in this pedon are: a.histic epipedon from 8 inches to 0; permafrost at 24 inches and saturated conditions above the permafrost. Loamy particle size class from 10 to 34 inches; pH >5.5 (1:1,H20) in control section.

The Tsana series is recognized for pedons where the organic mat has been burned or mechanically cleared. In these pedons, the permafrost and water table have dropped below the series control section.

The Tolsona series formerly classified as Sandy.

National Cooperative Soil Survey
U.S.A.