LOCATION ADIT MTEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed, frigid Aridic Lithic Ustorthents
TYPICAL PEDON: Adit gravelly coarse sandy loam, in rangeland (colors are for dry soil unless otherwise noted).
A--0 to 2 inches; brown (10YR 5/3) gravelly coarse sandy loam, dark brown (10YR 3/3) moist; weak fine granular structure; soft, very friable, slightly sticky and nonplastic; few very fine and fine roots; 25 percent, mainly fine, gravels; neutral (pH 6.8); clear wavy boundary. (0 to 4 inches thick)
BC--2 to 7 inches; pale brown (10YR 6/3) very gravelly coarse sand, brown (10YR 4/3) moist; single grain; loose, nonsticky and nonplastic; few fine and very fine roots; 40 percent, mainly fine, gravels; neutral (pH 6.6); abrupt wavy boundary. (2 to 10 inches thick)
Cr--7 to 14 inches; soft, weathered granite bedrock.
R--14 inches; hard granite bedrock.
TYPE LOCATION: Silver Bow County, Montana; 1,750 feet north and 2,200 feet west of the SE corner of sec. 5, T. 4 N., R. 9 W. Ramsey topographic quadrangle, UTM zone 12T, 0365296E, 5109141N, NAD 27
RANGE IN CHARACTERISTICS:
Mean annual soil temperature 40 to 44 degrees F., frigid temperature regime.
Soil moisture control section the paralithic contact; dry more than four-tenths of the cumulative days per year when the soil temperature at a depth of 20 inches is at or above 41 degrees F. Ustic moisture regime that borders on aridic
Depth to paralithic contact 4 to 10 inches
Depth to lithic contact 6 to 20 inches
The Cr horizon may lacking in some profiles with a lithic contact 10 inches or less deep.
Surface stones and boulders 0 to 5 percent.
The surface, when mixed to a depth of 7 inches or to the lithic or paralithic contact, whichever is shallower, does not meet the color requirements for a mollic epipedon.
A Horizon
Value: 4, 5, or 6 dry; 2, 3, or 4 moist
Chroma: 2 or 3
Texture: coarse sandy loam or loamy coarse sand
Clay content: 4 to 12 percent
Rock fragments: 13 to 60 percent--0 to 30 percent cobbles, stones and boulders, 8 to 40 percent, mainly fine, gravel
Reaction: pH 5.6 to 6.8
BC Horizon
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture: loamy coarse sand or coarse sand
Clay content: 2 to 8 percent
Rock fragments: 35 to 85 percent--0 to 35 percent cobbles, stones, and boulders, 20 to 50 percent, mainly fine, gravel
Reaction: pH 6.4 to 7.2
COMPETING SERIES: There are no competing series. The closely related Zonite series has a cryic temperature regime and an ustic moisture regime that does not border on aridic.
GEOGRAPHIC SETTING:
Landform- hillslopes, ridges, and bedrock floored pediments
Elevation - 5,120 to 6,300 feet
Slope - 2 to 45 percent
Parent material - residuum from granite or other coarse grained igneous or metamorphic rocks
Climate - long cold winters; moist springs; warm, dry summers
Mean annual precipitation - 10 to 14 inches
Mean annual air temperature - 38 to 43 degrees F.
Frost-free period - 70 to 90 days
GEOGRAPHICALLY ASSOCIATED SOILS:
These are the Modess and Rockerjohn series. Modess soils have bedrock within 20 to 40 inches of the soil surface and accumulations of calcium carbonate in one or more subsoil horizons. Rockerjohn soils are very deep and have a weighted average of less than 35 percent rock fragments in the particle size control section. Both have mollic surface horizons. They occur on more linear to concave landscape positions relative to the Adit series.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; rapid permeability.
USE AND VEGETATION: Adit soils are primarily used for rangeland and as wildlife habitat. The native vegetation is mainly a sparse coverage of bluebunch wheatgrass, rubber rabbitbrush, needleandthread, sandberg bluegrass, fringed sagewort, Hood's phlox, cutleaf daisy and other miscellaneous subshrubs and forbs. Scattered Douglas-fir and rocky mountain juniper are common.
DISTRIBUTION AND EXTENT: Adit soils are of limited extent in foothills of southwestern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Silver Bow County, Montana, 2007.
REMARKS: Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the soil surface to 2 inches (A horizon); a paralithic contact of soft granite bedrock at 7 inches (Cr horizon); a lithic contact at 14 inches (R horizon); a particle-size control section from 0 to 7 inches (A, BC horizons). Adit soils have a frigid temperature regime and an ustic moisture regime that borders on aridic. Gravels throughout the profile are primarily fine pea gravel less than 7 mm in diameter.