LOCATION COSLAW MTEstablished Series
TAXONOMIC CLASS: Ashy-skeletal, glassy, shallow Ustivitrandic Haplocryepts
TYPICAL PEDON: Coslaw gravelly ashy sandy loam, in non-stocked forest (colors are for dry soil unless otherwise noted).
A--0 to 4 inches; grayish brown (2.5Y 5/2) gravelly ashy sandy loam, very dark grayish brown (2.5Y 3/2) moist; weak fine granular structure; slightly hard, very friable, nonsticky and nonplastic; few very fine and fine roots; 25 percent gravel; strongly acid (pH 5.4); clear wavy boundary. (2 to 6 inches thick)
Bw--4 to 18 inches; light brownish gray (2.5Y 6/2) very gravelly ashy sandy loam, very dark grayish brown (2.5Y 3/2) moist; weak medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; few very fine and fine roots; common very fine pores; 10 percent cobbles and 40 percent gravel; neutral (pH 6.6); gradual wavy boundary. (8 to 14 inches thick)
Cr--18 to 31 inches; light gray (5Y 7/2) decomposing welded tuff bedrock that crushes to very gravelly ashy sandy loam; neutral (pH 6.8).
R--31 inches; white fractured hard welded tuff bedrock.
TYPE LOCATION: Deer Lodge County, Montana; 2250 feet east and 1500 feet south of the NW corner of sec. 16, T. 3 N., R. 11 W.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 32 to 40 degrees F.
Mean summer soil temperature - 40 to 46 degrees F.
Moisture control section - between 8 and 18 inches, or between 8 inches and the paralithic contact if less than 18 inches.
Volcanic glass - 30 to 50 percent in the coarse silt and sand fraction.
Acid oxalate Al + 1/2 Fe - .12 to .20 percent
Depth to Cr horizon - 12 to 18 inches.
Depth to R horizon - 24 to 40 inches.
A horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 3, 4 or 5 moist
Chroma: 1 or 2
Texture: ashy sandy loam or ashy loam
Clay content: 10 to 20 percent
Rock fragments: 15 to 50 percent--0 to 15 percent cobbles and stones, 10 to 40 percent gravel
Reaction: pH 5.1 to 6.5
Bw horizon - Hue: 10YR, 2.5Y or 5Y
Value: 5, 6 or 7 dry, 3, 4, 5 or 6 moist
Chroma: 1 or 2
Texture: ashy loam, ashy sandy clay loam, ashy coarse sandy loam or ashy sandy loam
Clay content: 10 to 22 percent
Rock fragments: 35 to 60 percent--5 to 20 percent cobbles and stones, 30 to 40 percent gravel
Reaction: pH 5.6 to 7.3
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform- hills; mountains.
Elevation - 5,400 to 7,800 feet.
Slope - 15 to 70 percent.
Parent material - residuum from welded tuff or rhyolite bedrock.
Climate - long, cold winters; cold, moist springs; short, cool summers.
Mean annual precipitation - 20 to 30 inches.
Mean annual air temperature - 30 to 37 degrees F.
Frost-free period - 30 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained, moderate permeability.
USE AND VEGETATION: Coslaw soils are mainly used for woodland, watershed, and as wildlife habitat. The potential overstory vegetation is mainly: subalpine fir, lodgepole pine, whitebark pine (at higher elevations), and Douglas-fir (at lower elevations). Understory vegetation: grouse whortleberry, Oregongrape, pinegrass, white spiraea and common juniper.
DISTRIBUTION AND EXTENT: Coslaw soils are of small extent in southwestern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Deer Lodge County, Montana, 1999.
REMARKS: Soil interpretive record: MT1744. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the surface to 6 inches (A and upper part of Bw horizons); a cambic horizon from 4 to 18 inches (Bw horizon); a particle size control section from 10 to 18 inches (Bw horizon); a layer of decomposing welded tuff from 18 to 31 inches (Cr horizon); welded tuff bedrock at 31 inches (R horizon). Coslaw soils have a cryic temperature regime and an ustic moisture regime bordering on udic.
The 3/2008 description reflects a change in classification from Ashy-skeletal, glassy, shallow Vitrandic Eutrocryepts to Ashy-skeletal, glassy, shallow Ustivitrandic Haplocryepts due to revision of the cryepts great groups and subgroups. The competing series section was not updated and should be reviewed after all the cryepts have been re-classified.