LOCATION WISSIKIHON MTEstablished Series
TAXONOMIC CLASS: Sandy, mixed Ustic Haplocryolls
TYPICAL PEDON: Wissikihon gravelly coarse sandy loam, in grassland (colors are for dry soil unless otherwise noted).
A1--0 to 3 inches; dark grayish brown (10YR 4/2) gravelly coarse sandy loam, very dark grayish brown (10YR 3/2) moist; moderate medium granular structure; soft, very friable, non-sticky and non-plastic; many very fine, fine, and medium roots; 20 percent fine and medium gravel; slightly acid (pH 6.2); clear smooth boundary.
A2--3 to 8 inches; dark brown (10YR 3/3) gravelly coarse sandy loam, very dark brown (10YR 2/2) moist; weak medium subangular blocky structure; soft, very friable, slightly sticky and non-plastic; many very fine and common fine and medium roots; few fine and very fine tubular pores; 20 percent fine and medium gravel; slightly acid (pH 6.2); clear smooth boundary. (combined thickness of A1 and A2 horizons is 6 to 15 inches)
Bw--8 to 14 inches; brown (10YR 5/3) gravelly coarse sandy loam, brown (10YR 4/3) moist; weak medium prismatic structure parting to weak medium subangular blocky; slightly hard, very friable, slightly sticky and non-plastic; common very fine and fine and few medium roots; few very fine tubular pores; 30 percent fine gravel; slightly acid (pH 6.4); gradual clear boundary. (5 to 11 inches thick)
BC--14 to 48 inches; light brownish gray (10YR 6/2) gravelly loamy coarse sand, grayish brown (10YR 5/2) moist; massive; soft, loose, non-sticky and non-plastic; few very fine roots; 35 percent fine gravel; neutral (pH 6.6); gradual wavy boundary.
Cr--48 to 60 inches; soft, weathered granite bedrock.
TYPE LOCATION: Silver Bow County, Montana; 200 feet south and 2600 feet west of the NE corner of sec. 9, T. 2 N., R. 8 W. Butte South topographic quadrangle, Latitude 45 degrees 56 minutes 43 seconds N. and Longitude 112 degrees 36 minutes 4 seconds W.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature 38 to 42 degrees F., cryic temperature regime.
Soil moisture control section between 12 and 35 inches, dry in some or all parts for 90 or more cumulative days in normal years; not dry in all parts for more than half of the cumulative days. Ustic moisture regime
Mollic epipedon thickness - 7 to 15 inches
Depth to Cr horizon - 40 to 60 inches
These soils contain a high proportion of medium, coarse, and very coarse angular sand in the sand fraction inherent due to granitic parent materials.
Weighted average of rock fragments in the particle-size control section average 25 to 35 percent.
A Horizon Value: 3, 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture: coarse sandy loam, sandy loam or loamy coarse sand
Clay content: 6 to 16 percent
Rock fragment content: 5 to 50 percent--0 to 5 percent cobbles, 5 to 45 percent, mainly fine, gravel
Reaction: pH 5.6 to 6.8
Bw Horizon Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 or 3
Texture: coarse sandy loam or loamy coarse sand
Clay content: 6 to 18 percent
Rock fragment content: 15 to 35 percent, mainly fine, gravel
Reaction: pH 6.2 to 6.8
BC or C Horizons Value: 5, 6 or 7 dry; 4 or 5 moist
Chroma: 2, 3 or 4
Texture: loamy coarse sand or coarse sand
Clay content: 2 to 8 percent
Rock fragment content: 20 to 40 percent, mainly fine, gravel
Reaction: pH 6.4 to 7.4
Note: Thin strata of fine sand or loamy fine sand may be present in the BC or C horizons of some profiles.
COMPETING SERIES: These are the Bangston and Tomichi series. Bangston soils have a mollic epipedon thicker than 15 inches and Tomichi soils do not have a cambic horizon. Both the Bangston and Tomichi soils lack appreciable coarse sand and are very deep.
GEOGRAPHIC SETTING:
Landform- depositional areas on hillslopes, mountain slopes and bedrock floored pediments
Elevation - 5,130 to 7,610 feet
Slope - 1 to 45 percent
Parent material- colluvium from granite or other coarse grained igneous or metamorphic rocks
Climate - long cold winters; moist springs; cool, dry summers
Mean annual precipitation - 15 to 19 inches
Mean annual air temperature - 35 to 43 degrees F.
Frost-free period - 30 to 70 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Branham and Highrye series. Branham soils are coarse loamy, have a lithic contact within 20 to 40 inches of the soil surface and occur on more convex slope positions. Highrye soils are fine loamy with a thin argillic horizon and occur on more stable landscape positions.
DRAINAGE AND PERMEABILITY: Well drained; moderately rapid over rapid permeability.
USE AND VEGETATION: Wissikihon soils are used for rangeland and wildlife habitat. Native vegetation is mainly bluebunch wheatgrass, Idaho fescue, needleandthread, rubber rabbitbrush, western yarrow, and silvery lupine.
DISTRIBUTION AND EXTENT: Wissikihon soils are of limited extent in southwest Montana.
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MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Silver Bow County, Montana, 2006.
REMARKS: Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 8 inches (A1 and A2 horizons); a cambic horizon from 8 to 14 inches (Bw horizon); a particle-size control section from 10 to 40 inches (Bw and BC horizons); a paralithic contact at 48 inches. Wissikihon soils have a cryic temperature regime and an ustic moisture regime. Gravels throughout the profile are primarily fine pea gravel less than 10 mm in diameter and there is a high proportion of medium, coarse, and very coarse angular sand in the sand fraction, inherited from granitic parent material.