LOCATION ARLEN MTEstablished Series
TAXONOMIC CLASS: Ashy-skeletal, glassy, calcareous, frigid Lithic Ustorthents
TYPICAL PEDON: Arlen very gravelly sandy loam, in woodland (colors are for dry colors unless otherwise noted).
A--0 to 3 inches; light gray (2.5Y 7/2) very gravelly ashy sandy loam, dark grayish brown (2.5Y 4/2) moist; weak coarse granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and few fine roots; 30 percent pebbles, 10 percent cobbles; slightly alkaline (pH 7.6); abrupt wavy boundary. (1 to 5 inches thick)
BCk--3 to 9 inches; light gray (2.5Y 7/2) very gravelly ashy sandy loam, dark grayish brown (2.5Y 4/2) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and common fine roots; 40 percent pebbles, 10 percent cobbles; common fine threads and masses of lime; slightly effervescent; slightly alkaline (pH 7.6); clear wavy boundary. (4 to 12 inches thick)
Cr--9 to 13 inches; light gray (2.5Y 7/2) decomposing welded tuff bedrock. (3 to 6 inches thick)
R--13 inches; light gray (5Y 7/1), fractured, hard, welded tuff bedrock.
TYPE LOCATION: Deer Lodge County, Montana; 1700 feet east and 1600 feet north of the SW corner of sec. 18, T. 5 N., R. 10 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 38 to 42 degrees F.
Moisture control section - between 4 and 12 inches, or between 4 inches and the paralithic contact.
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 - 8 to 17 inches.
Depth to R horizon - 11 to 18 inches.
A horizon - Hue: 10YR or 2.5Y
Value: 3, 4, 5, 6 or 7 dry; 2, 3 or 4 moist
Chroma: 1 or 2
Clay content: 10 to 20 percent
Rock fragments: 35 to 45 percent--5 to 15 percent cobbles and stones, 10 to 30 percent pebbles
Reaction: pH 6.6 to 7.8
BCk horizon - Hue: 10YR or 2.5Y
Value: 4, 5, 6 or 7 dry, 3, 4 or 5 moist
Chroma: 2 or 3
Texture: sandy loam, loam or sandy clay loam
Clay content: 10 to 24 percent
Rock fragments: 35 to 60 percent--5 to 20 percent cobbles and stones, 30 to 40 percent pebbles
Calcium carbonate equivalent: 5 to 10 percent
Reaction: pH 6.6 to 7.8
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - hills; mountains.
Elevation - 5,200 to 6,200 feet.
Slope - 8 to 60 percent.
Parent material - residuum from welded tuff or rhylite bedrock.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 15 to 24 inches.
Mean annual air temperature - 36 to 40 degrees F.
Frost-free period - 70 to 90 days.
DRAINAGE AND PERMEABILITY: Well drained, moderate permeability.
USE AND VEGETATION: Arlen soils are mainly used for woodland, understory grazing, watershed, and as wildlife habitat. The potential native vegetation is mainly scattered Douglas-fir, Rocky Mountain juniper, limber pine, bitterbrush, common juniper, Oregongrape, bluebunch wheatgrass, Idaho fescue, sandberg bluegrass and rose.
DISTRIBUTION AND EXTENT: Arlen 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: MT1741. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the surface to 9 inches (A and BCk horizons); a horizon of secondary carbonate accumulation from 3 to 9 inches (BCk horizon); a particle size control section from the surface to 9 inches (A and BCk horizons); a layer of decomposing welded tuff from 9 to 13 inches (Cr horizon); welded tuff bedrock at 13 inches (R horizon). Arlen soils have a frigid temperature regime and an ustic moisture regime.