LOCATION CLARKIA IDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Aquandic Endoaqualfs
TYPICAL PEDON: Clarkia ashy silt loam, pasture, on a 1 percent slope at 2,750 feet elevation. When described on October 31, 1983, the soil was moist throughout. (Colors are for dry soils unless otherwise noted.)
A--0 to 8 inches; grayish brown (10YR 5/2) ashy silt loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine tubular pores; moderately acid (pH 5.6); clear wavy boundary. (4 to 8 inches thick)
Bw--8 to 15 inches; light yellowish brown (10YR 6/4) ashy silt loam, dark yellowish brown (10YR 4/4) moist; few fine distinct dark grayish brown (10YR 4/2) moist redox depletions; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine tubular pores; moderately acid (pH 5.6); gradual wavy boundary. (6 to 10 inches thick)
Bt--15 to 25 inches; very pale brown (10YR 7/3) silty clay loam, brown (10YR 5/3) moist; many fine distinct and prominent dark grayish brown (10YR 4/2) moist redox depletions and strong brown (7.5YR 5/6) moist redox concentrations; moderate medium and coarse subangular blocky structure; hard, firm, moderately sticky and moderately plastic; many very fine and fine roots; many very fine and fine tubular pores; few faint clay films on faces of peds and lining pores; few fine iron and manganese concretions; moderately acid (pH 5.8); gradual wavy boundary. (8 to 14 inches thick)
Btg--25 to 32 inches; pale yellow (2.5Y 8/2) silt loam, light brownish gray (2.5Y 6/2) moist; common fine prominent strong brown (7.5YR 5/6) and yellowish brown(10YR 5/4) moist redox concentrations; moderate medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; common very fine and fine tubular pores; few faint clay films on faces of peds and lining pores; few fine iron and manganese concretions; moderately acid (pH 5.6); gradual wavy boundary. (7 to 12 inches thick)
Cg1--32 to 49 inches; pale yellow (2.5Y 8/2) silt loam, light brownish gray (2.5Y 6/2) moist; common fine prominent strong brown (7.5YR 5/6) and yellowish brown (10YR 5/4) moist redox concentrations; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; few very fine and fine tubular pores; few very fine iron and manganese concretions; slightly acid (pH 6.2); abrupt wavy boundary. (12 to 20 inches thick)
Cg2--49 to 62 inches; light gray (2.5Y 7/2) silty clay loam, grayish brown (2.5Y 5/2) moist; many medium prominent strong brown (7.5YR 5/6) and yellowish brown (10YR 5/4) moist redox concentrations; massive; hard, firm, moderately sticky and moderately plastic; few very fine tubular pores; few very fine iron and manganese concretions; slightly acid (pH 6.4).
TYPE LOCATION: Shoshone County, Idaho; approximately 4 miles northwest of Clarkia; about 1,200 feet east and 1,300 feet south of the northwest corner of sec. 27, T. 43 N., R. 1 E.
RANGE IN CHARACTERISTICS:
Depth to seasonal high water table - 18 to 24 inches (February to June) Average annual soil temperature - 44 to 46 degrees F
Average summer soil temperature - 55 to 58 degrees F without an O horizon
Solum thickness - 30 to 42 inches
Volcanic glass content in the 0.02 to 2.0 mm fraction - 5 to 20 percent Acid-oxalate extractable Al + 1/2 Fe - 0.4 to 1.0 percent
Moist bulk density - 1.0 to 1.2 g/cc
Reaction - moderately acid to slightly acid
A horizon
Value - 4 or 5 dry, and 2 or 3 moist
Chroma - 1 through 3 dry or moist
Base saturation - 35 to 50 percent
Bw horizon
Value - 6 or 7 dry, and 4 or 5 moist
Chroma - 3 or 4 dry or moist
Bt horizon
Value - 6 or 7 dry, and 4 or 5 moist
Mottles - chroma 2 through 6 dry or moist
Texture - SICL, SIL
Clay content - 25 to 32 percent
Btg horizon
Hue - 10YR or 2.5Y
Value - 6 through 8 dry, and 4 through 6 moist
Mottles - distinct or prominent, value 4 or 5 moist, chroma 1 through 6 dry or moist
Texture - SIL, SICL
Clay content - 25 to 32 percent
Cg horizon
Hue - 10YR or 2.5Y
Value - 6 through 8 dry, and 4 through 6 moist
Chroma - 1 or 2 dry or moist
Mottles - value 4 or 5 moist, chroma 2 through 6 dry or moist
Texture - SIL, SICL, and GR-SIL, GR-SICL, CB-SIL, or CB-SICL below 48 inches in some pedons
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Clarkia soils are on floodplains, narrow valley bottoms, low stream terraces, and valley floors. Slopes range from 0 to 2 percent. The soils formed in alluvium derived from mixed sources. Elevation ranges from 2,700 to 3,200 feet. The average annual air temperature ranges from 43 to 46 degrees F and average annual precipitation is 35 to 45 inches. The frost-free period is from 80 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Helmer, Hobo (T), Pokey, Reggear (T), and Sly (T) soils. Helmer, Hobo, and Reggear soils are on higher terraces and are moderately well drained. Pokey soils are on low stream terraces and floodplains, and are coarse-loamy over sandy. Sly soils are on higher terraces and well drained.
DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff; moderately slow permeability. These soils are frequently flooded for brief periods from February through May.
USE AND VEGETATION: These soils are used for hay and pasture, recreation, and wildlife habitat. Potential natural vegetation is mainly western river alder, Douglas hawthorn, Nebraska sedge, tufted hairgrass, gland cinquefoil, common camas, and rush.
DISTRIBUTION AND EXTENT: Benewah County and Shoshone County, Idaho. This series is not extensive.
MLRA OFFICE RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Shoshone County, Idaho, 1993.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 8 inches (A horizon)
Argillic horizon - the zone from 15 to 32 inches (Bt and Btg horizons)
Particle-size control section - the zone from 15 to 32 inches (Bt and Btg horizons)