LOCATION ARCETTE MTEstablished Series
TAXONOMIC CLASS: Fragmental, mixed Ustic Haplocryepts
TYPICAL PEDON: Arcette extremely gravelly loam, forested (colors are for dry soil unless otherwise noted).
Oi--0 to 2 inches; slightly decomposed and undecomposed organic matter composed of pine needles, cones, and twigs. (0 to 2 inches thick)
A--2 to 4 inches; yellowish brown (10YR 5/4) extremely gravelly loam, dark yellowish brown (10YR 4/4) moist; moderate very fine granular structure; soft, very friable, nonsticky and nonplastic; many coarse, medium, fine, and very fine roots; 55 percent angular gravel and 10 percent angular cobbles; moderately acid (pH 5.8); clear wavy boundary. (1 to 9 inches thick)
Bw1--4 to 10 inches; brownish yellow (10YR 6/6) extremely gravelly loam, brown (7.5YR 4/4) moist; moderate fine granular structure; soft, very friable, slightly sticky and nonplastic; common coarse, medium, and fine roots; 55 percent angular gravel and 10 percent angular cobbles; moderately acid (pH 5.6); gradual wavy boundary.
Bw2--10 to 19 inches; brownish yellow (10YR 6/6) extremely gravelly loam, strong brown (7.5YR 5/6) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; few coarse roots and common medium and fine roots; 55 percent angular gravel and 20 percent angular cobbles; moderately acid (ph 5.6); gradual wavy boundary. (Combined thickness of Bw horizons is 6 to 19 inches)
C--19 to 60 inches; yellow (10YR 7/6) fragmental material, light brown (7.5YR 6/4) moist; few medium and fine roots; silt and very fine sand coating coarse fragments; 50 percent angular gravel and 45 percent angular cobbles.
TYPE LOCATION: Fergus County, Montana; about 1,650 feet east and 1,980 feet south of the NW corner of sec. 20, T. 17 N., R. 20 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 36 to 42 degrees F.
Depth to fragmental material - 5 to 20 inches from the mineral soil surface.
Some pedons have an E horizon in place of the A horizon.
A horizon - Hue: 7.5YR or 10YR
Value: 5, 6 or 7 dry; 4 or 5 moist
Chroma: 2, 3, 4, 5, or 6
Texture: loam or sandy loam
Clay content: 10 to 20 percent
Rock fragments: 60 to 90 percent--5 to 20 percent cobbles and stones; 55 to 70 percent gravel
Reaction: pH 5.1 to 6.5
Bw horizon - Hue: 7.5YR or 10YR
Value: 6, 7, or 8 dry; 4, 5, or 6 moist
Chroma: 2, 3, 4, 5, or 6
Texture: loam or sandy loam
Clay content: 10 to 20 percent
Rock fragments: 60 to 90 percent--10 to 25 percent angular cobbles and stones; 50 to 65 percent angular gravel
Reaction: pH 5.1 to 6.5
C horizon - Rock fragments: 80 to 95 percent--very thin coating of silt and very fine sand on surface of fragments--35 to 40 percent angular cobbles and stones; 45 to 55 percent angular gravel
Reaction: pH 5.1 to 6.5
COMPETING SERIES:
Cuberant (UT) - has a lithic contact at 20 to 40 inches.
GEOGRAPHIC SETTING:
Landform - ridge tops and mountain slopes.
Elevation - 5,000 to 7,800 feet.
Slope - 15 to 60 percent.
Parent material - residuum or colluvium derived from weathered acid igneous rock.
Climate - long, cold winters; moist cool springs; cool summers.
Mean annual precipitation - 20 to 30 inches.
Mean annual temperature - 34 to 42 degrees F.
Frost-free period - 50 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: none listed.
DRAINAGE AND PERMEABILITY: Excessively drained; rapid permeability.
USE AND VEGETATION: Arcette soils are used mainly for forest products, watershed, and recreation. Potential native vegetation is mainly lodgepole pine and white spruce with a sparse understory of grouse whortleberry, white spiraea, kinnikinnick, and common juniper.
DISTRIBUTION AND EXTENT: Arcette soils are of small extent in the mountains of central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Fergus County, Montana, 1979.
REMARKS: Soil Interpretations Record: MT0338. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from 2 to 9 inches (A and part of Bw1 horizon); a cambic horizon from 4 to 19 inches (Bw1 and Bw2 horizons; fragmental material from 19 to 60 inches (C horizon); a particle-size control section from 10 to 40 inches (Bw2 and part of C horizon). Arcette soils have a cryic soil temperature regime and an ustic soil moisture regime.
The 3/2008 description reflects a change in classification from Fragmental, mixed Ustic Eutrocryepts to Fragmental, mixed Ustic 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.