LOCATION CASTAN IDEstablished Series
TAXONOMIC CLASS: Ashy-skeletal, glassy Humic Vitricryands
TYPICAL PEDON: Castan cobbly silt loam, supporting a lodgepole pine/grouse whortleberry plant community type, woodland; on a concave slope of 30 percent with a north aspect at about 6,840 feet elevation. (Colors are for air dry soil unless otherwise noted.)
Oi--0 to 1 inch; forest litter of needles, twigs and leaves; abrupt smooth boundary.
A1--1 to 12 inches; brown (10YR 5/3) cobbly silt loam, dark brown (10YR 3/3) moist; weak coarse subangular blocky structure parting to moderate fine granular; soft, very friable, nonsticky and slightly plastic; many very fine, common fine, and few medium and coarse roots; many very fine irregular pores; 10 percent pebbles,10 percent cobbles, trace stones and boulders; moderately acid (pH5.6); clear smooth boundary.
A2--12 to 17 inches; brown (10YR 5/3) cobbly loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; soft, very friable, nonsticky and slightly plastic; many very fine, common fine, and few medium and coarse roots; many very fine tubular pores; 10 percent pebbles, 10 percent cobbles, trace stones and boulders; moderately acid (pH 5.6); clear wavy boundary. (combined thickness of A horizons, 10 to 16 inches)
B/E--17 to 31 inches; light yellowish brown (10YR 6/4) and very pale brown (10YR 7/3) very gravelly sandy loam, dark yellowish brown (10YR 4/4) and brown (10YR 5/3) moist; 80 percent B material and 20 percent E material in a fine (less than 5 mm) irregular matrix; moderate medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; many very fine and few fine, medium and coarse roots; many very fine tubular pores; 40 percent pebbles, 10 percent cobbles, a trace stones and boulders; moderately acid (pH 6.0); clear smooth boundary. (10 to 24 inches thick)
E/B--31 to 39 inches; very pale brown (10YR 7/3) and light yellowish brown (10YR 6/4) extremely gravelly sandy loam, brown (10YR 5/3) and dark yellowish brown (10YR 4/4) moist; 80 percent E material and 20 percent B material in a medium (5 to 15 mm) irregular matrix; weak medium subangular blocky parting to weak fine granular structure; slightly hard, very friable, nonsticky and nonplastic; common very fine and few fine and medium roots; many very fine irregular pores; 50 percent pebbles, 10 percent cobbles, a trace of stones and boulders; moderately acid (pH 6.0); clear smooth boundary. (0 to 10 inches thick)
B/E'--39 to 50 inches; pale brown (10YR 6/3) and very pale brown (10YR 8/2) extremely gravelly sandy loam, brown (10YR 4/3) and light brownish gray (10YR 6/2) moist; 50 percent B material and 50 percent E material in a coarse (greater than 15 mm) irregular matrix; weak fine subangular blocky structure (B portion) and weak fine granular structure (E portion); slightly hard (B portion) and soft (E portion), very friable, nonsticky and nonplastic; few very fine roots; many very fine tubular pores (B portion) and many very fine irregular pores (E portion); 50 percent pebbles, 10 percent cobbles, a trace of stones and boulders; slightly acid (pH 6.2); clear smooth boundary. (5 to 15 inches thick)
BC--50 to 60 inches; pale brown (10YR 6/3) extremely gravelly loamy sand, brown (10YR 4/3) moist; weak fine subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; many very fine irregular pores; continuous very pale brown (10YR 8/2) uncoated silt grains capping cobbles stones and boulders, light brownish gray (10YR 6/2) moist; 65 percent pebbles, 10 percent cobbles, a trace of stones and boulders; slightly acid (pH 6.4).
TYPE LOCATION: Fremont County, Idaho; about 35 miles north of Ashton, Idaho; about 600 feet west and 50 feet south of the northeast corner of section 14, T. 14 N., R, 44 E.; Latitude - 44 degrees, 32 minutes, 43 seconds North; Longitude - 111 degrees, 13 minutes, 53 seconds West.
RANGE IN CHARACTERISTICS:
Umbric epipedon thickness - 10 to 16 inches.
Thickness of andic soil properties - 15 to 30 inches.
Depth to BC horizon - 30 to 50 inches.
Rock fragments in the particle-size control section, weighted average - 35 to 65 percent.
Mean annual soil temperature - 34 to 39 degrees F.
Mean summer soil temperature - 39 to 44 degrees F.
Moisture control section - between 12 and 36 inches. The soil is dry throughout the moisture control section for less than 30 consesecutive days during the four months following the summer solstice.
O horizon
Thickness - commonly 0 to 2 inches thick
Form - commonly forest litter of needles, twigs and leaves on lightly or undisturbed pedons and absent on pedons where recent, heavy mechanical disturbance has occurred.
A horizons
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Volcanic glass content - 30 to 75 percent in the 0.02 to 2.0 mm fraction
Ammonium oxalate extractable Al plus 1/2 Fe - 0.4 to 1.5 percent
Bulk density - 0.90 to 1.30 grams per cubic centimeter
Phosphate retention - 40 to 70 percent
Base saturation by ammonium acetate - 10 to 30 percent
B/E or E/B horizons Value, B portion - 6 or 7 dry, 4 or 5 moist
E portion - 7 or 8 dry, 5 or 6 moist
Chroma, B portion - 3 or 4 dry or moist
E portion - 2 or 3 dry or moist
Texture, less than 2 mm fraction - silt loam, sandy loam or loam
Rock fragments - 35 to 65 percent
Pebbles - 25 to 50 percent
Cobbles - 5 to 20 percent
Stones or boulders - 0 to 20 percent
Reaction - moderately acid or slightly acid
Volcanic glass content - 30 to 75 percent in the 0.02 to 2.0 mm fraction
Ammonium oxalate extractable Al plus 1/2 Fe - 0.2 to 1.0 percent
Phosphate retention - 35 to 70 percent
Bulk density - 1.4 to 1.6 g/cc
Base saturation by ammonium acetate - 30 to 60 percent
Other - 15 to 85 percent B or E materials by volume
BC horizon Hue - 7.5YR, 10YR or 2.5Y
Value - 6 or 7 dry, 4 to 6 moist
Chroma - 2 or 3 dry or moist
Texture, less than 2 mm fraction - loamy sand or loamy coarse sand
Rock fragments - 50 to 80 percent
Pebbles - 30 to 65 percent
Cobbles - 5 to 30 percent
Stones or boulders - 0 to 20 percent
Ammonium oxalate extracatble Al plus 1/2 Fe - less than 0.4 percent
Reaction - slightly acid or neutral
Volcanic glass content - greater than 50 percent in the 0.02 to 2.0 mm fraction
Bulk density - 1.4 to 1.6 g/cc
Base saturation by ammonium acetate - 50 to 80 percent
Phosphate retention - 35 to 60 percent
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: The Castan soils are on escarpments of volcanic plateaus. Slopes are 30 to 50 percent and are dominantly concave in shape. This soil formed in local alluvium, colluvium or residuum from tephra and loess. The rock fragments and sand size fraction are dominantly obsidian. Elevations range from 6,500 to 8,000 feet. The average annual precipitation ranges from 30 to 60 inches. Average annual air temperature is 30 to 37 degrees F. Frost may occur at anytime throughout the year.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the proposed Dashiki, Lasac and Oleo series. Dashiki and Oleo soils occur on adjacent volcanic plateaus. Dashiki soils have an ochric epipedon and are moderately deep over substratum layers of tephra. Oleo soils have an argillic horizon and average less than 35 percent rock fragments throughout the solum. Lasac soils occur intermixed with the Castan soils on convex slope positions. They are less than 20 inches to substratum layers of tephra.
DRAINAGE AND PERMEABILITY: Well drained; slow to moderate runoff; moderately rapid permeability.
USE AND VEGETATION: Castan soils are used for recreation, woodland and wildlife habitat. These soils commonly support a lodgepole pine/grouse whortleberry plant community type. The potential native vegetation is a whitebark pine/grouse whortleberry plant association.
DISTRIBUTION AND EXTENT: Southeastern Idaho and northwestern Wyoming. The soil is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Targhee National Forest, Fremont County, Idaho, 1997.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Umbric epipedon - the zone from 1 to 17 inches (A1 and A2 horizons).
Cambic horizon - the zone from 17 to 50 inches (B/E, E/B and B/E' horizons).
Particle-size control section - the zone from 1 to 41 inches (A1, A2, B/E, E/B and a portion of the B/E' horizons).
Andic soil properties - the zone from 1 to 17 inches (the A1 and A2 horizons).
Moisture regime - udic.