LOCATION ASHBON MTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, nonacid, frigid Lithic Ustorthents
TYPICAL PEDON: Ashbon very gravelly sandy loam, coniferous forest (colors are for dry soil unless otherwise noted).
Oi--0 to 1 inches; slightly decomposed needles, twigs and leaves.
A--1 to 6 inches; pale brown (10YR 6/3) very gravelly sandy loam, dark brown (10YR 4/3) moist; moderate very fine and fine granular structure; soft, very friable, slightly sticky and slightly plastic; common very fine and fine roots; common very fine pores; 35 percent pebbles, 3 percent cobbles; slightly acid (pH 6.4); clear smooth boundary. (2 to 8 inches thick)
C--6 to 16 inches; light brownish gray (10YR 6/2) very gravelly sandy loam, dark grayish brown (10YR 4/2) moist; massive; soft, very friable, slightly sticky and slightly plastic; common fine and medium roots; common fine pores; 50 percent pebbles, 5 percent cobbles; moderately acid (pH 6.0); clear smooth boundary. (9 to 12 inches thick)
R--16 inches; Volcanic mudflow breccia bedrock.
TYPE LOCATION: Sweet Grass County, Montana; 250 feet west and 450 feet south of the NE corner of sec. 9, T. 2 S., R. 15 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between the depths of 4 and 12 inches or between 4 inches and the lithic contact if less than 12 inches.
Rock fragments - dominantly angular pebbles of breccia and mixed igneous rock.
Depth to bedrock - 10 to 20 inches.
The surface when mixed to 7 inches does not meet the requirements for a mollic epipedon.
A horizon - Hue: 2.5Y or 10YR
Value: 5, 6 or 7 dry; 3, 4 or 5 moist
Chroma: 2 or 3
Texture: sandy loam or loam
Clay content: 5 to 25 percent
Rock fragments: 15 to 60 percent--0 to 5 percent angular cobbles, 15 to 55 percent angular pebbles
Reaction: pH 6.1 to 7.3
C horizon - Hue: 2.5Y or 10YR
Value: 5, 6 or 7 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: sandy loam or loam
Clay content: 5 to 25 percent
Rock fragments: 50 to 80 percent--0 to 15 percent angular cobbles, 50 to 65 percent angular pebbles
Reaction: pH 5.6 to 7.3
COMPETING SERIES:
Ashbray (MT) - did not form in residuum from volcanic mudflow breccia; is somewhat excessively drained.
Valto (CO) - has 15 percent or more cobbles and stones; did not form in residuum derived from volcanic mudflow breccia.
GEOGRAPHIC SETTING:
Landform - mountains and hills; generally south aspects
Elevation - 3,900 to 6,200 feet.
Parent material - residuum from volcanic mudflow breccia.
Slope - 8 to 60 percent.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 15 to 20 inches, most of which falls during spring and early summer.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free period - 70 to 120 days.
DRAINAGE AND PERMEABILITY: Well drained; moderately rapid permeability.
USE AND VEGETATION: Ashbon soils are used mainly for grazeable woodland, the production of forest products, and wildlife. Potential native vegetation is mainly ponderosa pine and Douglas-fir, with an understory of bunchgrass. Some lesser sloping areas are used for range. The principle vegetation in these areas are Idaho fescue, bluebunch wheatgrass, Columbia needlegrass, needleandthread, prairie junegrass, and big sagebrush.
DISTRIBUTION AND EXTENT: Ashbon soils are of moderate extent in south central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Sweetgrass County, Montana, 1999.
REMARKS: Soil Interpretations Records: MT0055, MT0681. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the soil surface to 6 inches, mixed (A, C horizons); a lithic contact at 16 inches (R horizon); a particle-size control section from 10 to 16 inches (C horizon). Ashbon soils have a frigid temperature regime and an ustic moisture regime.