LOCATION KECHUMSTUK AK
Tentative Series
Rev: DKS/JPM
02/2022
KECHUMSTUK SERIES
The Kechumstuk series consists of very deep, very poorly drained soils formed in organic matter and silty alluvium on alluvial plains. Slopes range from 0 to 2 percent. Mean annual temperature is 21 to 28 degrees F., and the average annual precipitation is 9 to 13 inches.
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, nonacid Histic Cryaquepts
TYPICAL PEDON: Kechumstuk peat - on a 0 percent slope under shrub birch at 1050 feet elevation. (All colors are for moist soil)
Oi--0 to 5 inches; very dark grayish brown (10YR 3/2) slightly decomposed peat; many very fine to medium roots; moderately acid (pH 6.0); clear smooth boundary.
Oa--5 to 13 inches; very dark grayish brown (10YR 3/2) highly decomposed muck; many very fine to fine roots; slightly acid (pH 6.2); clear smooth boundary.
Bg1--13 to 24 inches; gray (5Y 5/1) and olive gray (5Y 2.5/1) silt loam; massive; slightly sticky and slightly plastic; few very fine roots; neutral (pH 6.6); clear wavy boundary.
Bg2--24 to 51 inches; gray (5Y 5/1) and light olive brown (2.5Y 5/4) silt loam; massive; slightly sticky and slightly plastic; neutral (pH 6.6); clear wavy boundary.
C--51 to 80 inches; dark yellowish brown (10YR 4/4) and dark grayish brown (2.5Y 4/2) silt loam; massive; slightly sticky and slightly plastic; neutral (pH 6.6).
TYPE LOCATION: Gerstle River Area, Alaska; about 11 miles east of Delta Junction; SE 1/4 of the NW 1/4 of section 11, T.10S., R. 12 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 32 to 35 degrees F.
The O horizon ranges from slightly decomposed in the upper part to highly decomposed in the lower part. Reaction is moderately acid or slightly acid.
The Bg horizon has matrix hue of 2.5Y, 5Y, or 5GY; value from 3 to 6, and chroma from 0 to 2. Mottles of secondary colors with hue of 10YR or 2.5Y, value from 3 to 5, and chroma from 2 to 4 may be present. Texture is silt loam or very fine sandy loam. Few very thin strata of loamy fine sand or loamy very fine sandy are present in some pedons. Buried O or A horizons are present in some pedons. Reaction is slightly acid or neutral.
The C horizon has hue of 10YR or 2.5Y, value from 3 to 5, and chroma from 2 to 4. Texture is silt loam or very fine sandy loam. Few very thin strata of loamy fine sand or loamy very fine sand are present in some pedons. Sand and gravel may occur more than 40 inches below the top of the mineral material.
COMPETING SERIES: This is the
Slikok series. Slikok soils have a pH less than 5.5 (1:1, H2O) throughout the control section.
GEOGRAPHIC SETTING: Kechumstuk soils are on alluvial plains in broad valleys with slopes of 2 percent or less. They formed in silty alluvium in areas where the water table is near the surface due to groundwater discharge. Sandy or gravelly alluvium may be present below 40 inches. The climate is boreal continental, with short, warm summers and long, cold winters. Mean annual precipitation is 9 to 13 inches, approximately one third of which falls as snow. The mean annual temperature is 21 to 28 degrees F.
DRAINAGE AND PERMEABILITY: Very poorly drained. Very slow runoff. Moderate permeability.
USE AND VEGETATION: Kechumstuk soils support forest of tamarack and black spruce, usually stunted and sparse, over shrub birch and sedges. Treeless openings are present. The soils are used for wildlife habitat and watershed management.
DISTRIBUTION AND EXTENT: Interior Alaska. The extent of the series is currently unknown.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: WASILLA, ALASKA
SERIES PROPOSED: Gerstle River Area, Alaska, 1992.
REMARKS: Diagnostic features and horizons include: a histic epipedon; low chroma matrix in the upper 27 inches of mineral soil; cryic temperature regime; weighted average particle size of coarse-silty in the control section; and pH greater than 5.5 (1:1,H2O) throughout the mineral soil.
The strong gleying, weakly acid or nonacid reaction, and lack of permafrost in Kechumstuk soils result from groundwater discharge. The soil is saturated within 10 inches of the mineral surface during most of the summer.
National Cooperative Soil Survey
U.S.A.