LOCATION TONSINA                 AK

Established Series
Rev. MHC/JPM
02/2022

TONSINA SERIES


The Tonsina series consists of well drained soils formed in silty loess over loamy glacial till. Tonsina soils are on drumlins, till plains, and hills. Slopes range from 0 to 20 percent. Mean annual temperature is about 26 degrees F. and the average annual precipitation is about 12 inches.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive Cumulic Haplocryolls

TYPICAL PEDON: Tonsina silt loam - on a 1 percent slope under aspen forest at 1400 feet elevation.

Oi--2 inches to 0; undecomposed mat of roots, moss, leaves, and other forest litter; abrupt smooth boundary. (1 to 5 inches thick)

A--0 to 2 inches; very dark grayish brown (10YR 3/2) moist silt loam, light grayish brown (10YR 5/2) dry; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; many roots of all sizes; neutral (pH 7.2); clear smooth boundary. (1 to 7 inches thick)

Bw1--2 to 4 inches; dark brown (7.5YR 3/2) moist silt loam, brown (7.5YR 5/4) dry; convoluted streaks and patches of brown (7.5YR 4/4); weak thin platy structure; soft, very friable, nonsticky and nonplastic; many very fine, fine and medium roots; neutral (pH 7.2); clear wavy boundary. (0 to 15 inches thick)

Bw2--4 to 16 inches; dark brown (10YR 3/3) moist silt loam, grayish brown (10YR 5/2) dry; few medium faint convoluted streaks and patches of dark yellowish brown (10YR 3/4); moderate thin platy structure; slightly hard, friable, nonsticky and nonplastic; common very fine and fine roots; neutral (pH 7.2); abrupt broken boundary. (0 to 11 inches thick)

2C1--16 to 19 inches; very dark grayish brown (2.5Y 3/2) moist gravelly sandy loam; massive; very friable, nonsticky and nonplastic; few fine and very fine roots; mildly alkaline (pH 7.4); 15 to 20 percent gravel; abrupt broken boundary. (4 to 20 inches thick)

2C2--19 to 35 inches; dark gray (5Y 4/1) moist sandy loam; weak medium platy structure parting to weak fine subangular blocky; soft, very friable, nonsticky and nonplastic; few fine roots; moderately alkaline (pH 8.2); about 10 percent gravel, few subrounded cobbles; clear smooth boundary. (8 to 19 inches thick)

2C3--35 to 54 inches; dark gray (5Y 4/1) moist fine sandy loam; weak medium platy structure parting to weak fine subangular blocky; soft, very friable, nonsticky and nonplastic; few fine roots; moderately alkaline (pH 8.2); 5 to 10 percent gravel, few subrounded cobbles; clear smooth boundary. (0 to 19 inches thick)

2C4--54 to 60 inches; gray (5Y 5/1) moist fine sandy loam; massive; soft, very friable, nonsticky and nonplastic; moderately alkaline (pH8.2).

TYPE LOCATION: Copper River Area, Alaska; 5 miles northwest of the village of Kenny Lake; about 2200 feet east and 250 feet north of the SW corner of section 5, T.1S., R.2E., Copper River Meridian.

RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 32 to 35 degrees F. Thickness of the loess mantle ranges from 15 to 38 inches. Thickness of the solum ranges from 9 to 16 inches. The weighted average particle size of the control section has less than 18 percent clay, less than 35 percent rock fragments, and more than 15 percent fine sand or coarser.

The A horizon has hue of 7.5YR or 10YR; moist value of 2 or 3; moist chroma of 1, 2, or 3. Colors occur in horizontal or convoluted streaks and patches. Texture is silt, mucky silt loam, silt loam, or very fine sandy loam. Reaction is slightly acid or neutral.

The B horizons, when present, have hue of 7.5YR or 10YR; moist value of 3, 4, or 5; moist chroma of 2,3, or 4. Colors occur in horizontal or convoluted streaks and patches. Texture is silt, silt loam, or very fine sandy loam. Reaction is neutral of mildly alkaline.

The 2C horizons have hue of 2.5Y or 5Y; moist value of 3, 4, or 5; and moist chroma of 1 or 2. Texture is loam, sandy loam, or fine sandy loam. Rock fragment content ranges from 0 to 25 percent subangular gravel and 0 to 15 percent subangular cobble. Reaction is neutral to moderately alkaline.

COMPETING SERIES: There are no competing series in the same family.

GEOGRAPHIC SETTING: Tonsina soils formed in a silty loess mantle overlying loamy glacial till on drumlins, till plains, and hills. Slopes range from 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 is 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: This is the Copper River series on the same landforms. Copper River soils are the permafrost counterpart of the Tonsina series. The organic mat of the Copper River soils is undisturbed, resulting in better insulation, lower soil temperature, and permafrost within the control section.

DRAINAGE AND PERMEABILITY: Well drained; runoff is slow to rapid; permeability is moderate.

USE AND VEGETATION: Most areas of Tonsina soils have native vegetation of white spruce, quaking aspen, paper birch, and willows. Most areas have been burned, resulting in the transition from Copper River to Tonsina soils. The successional state of vegetation in a given area is closely related to the fire history. Small areas are cleared and used for small grains, grass, and vegetables.

DISTRIBUTION AND EXTENT: Copper River Basin. The series is of moderate extent. SERIES PROPOSED: Copper-Chitina Area, Alaska, 1962.

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

REMARKS: Diagnostic horizons and features recognized in this pedon include: a mollic epipedon from 0 to 16 inches; irregular organic carbon decrease with depth in epipedon; cryic temperature regime; weighted average particle size of coarse-loamy from 10 to 40 inches.

The Tonsina series is a thawed counterpart of the permafrost Copper River series.

ADDITIONAL DATA: Laboratory data is available for this soil: NSSL numbers S81AK-612-22.


National Cooperative Soil Survey
U.S.A.