LOCATION AHRS IDEstablished Series
TAXONOMIC CLASS: Ashy-skeletal over loamy-skeletal, amorphic over isotic, frigid Typic Udivitrands
TYPICAL PEDON: Ahrs gravelly ashy silt loam, forest; on an east facing convex slope of 58 percent at 4,160 feet elevation. When described on August 3, 1981, the soil was dry throughout. (Colors are for dry soil unless otherwise stated.)
Oi--0 to 1 inch; slightly decomposed needles, leaves, and twigs.
Oe--1 to 2 inches; decomposed organic matter mixed with Mt. St. Helens volcanic ash.
A--2 to 8 inches; grayish brown (10YR 5/2) gravelly ashy silt loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine, common medium, and few coarse roots; many very fine and common fine tubular and irregular pores; 20 percent gravel and 5 percent cobbles; neutral (pH 7.0); clear wavy boundary. (2 to 6 inches thick)
Bw1--8 to 20 inches; yellowish brown (10YR 5/4) very cobbly ashy silt loam, dark yellowish brown (10YR 3/4) moist; weak fine and medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine, common medium, and few coarse roots; common very fine and fine tubular and irregular pores; 20 percent gravel and 20 percent cobbles; neutral (pH 6.8); clear wavy boundary. (12 to 18 inches thick)
2Bw2--20 to 32 inches; light yellowish brown (10YR 6/4) extremely cobbly loam, dark yellowish brown (10YR 4/4) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine, medium, and few coarse roots; common very fine and fine, and few medium tubular and irregular pores; 20 percent gravel, 30 percent cobbles, and 15 percent stones; slightly acid (pH 6.5); clear wavy boundary. (12 to 20 inches thick)
2C1--32 to 48 inches; very pale brown (10YR 7/4) extremely cobbly loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine, few medium and coarse roots; common very fine, fine, and few medium tubular and irregular pores; 20 percent gravel, 30 percent cobbles, and 15 percent stones; slightly acid (pH 6.5); gradual wavy boundary. (15 to 20 inches thick)
2C2--48 to 59 inches; very pale brown (10YR 7/4) extremely cobbly loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; common very fine and fine tubular and irregular pores; 35 percent gravel, 35 percent cobbles, and 15 percent stones; slightly acid (pH 6.4); gradual wavy boundary. (5 to 18 inches thick)
2C3--59 to 62 inches; very pale brown (10YR 7/4) extremely cobbly loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; common very fine and fine tubular pores; 35 percent gravel, 40 percent cobbles, and 15 percent stones; slightly acid (pH 6.4).
TYPE LOCATION: Benewah County, Idaho; about 1.5 miles southeast of St. Joe Baldy, 2,000 feet east and 1,000 feet south of the northwest corner of section 7, T. 46 N., R. 1 E. Latitude 47 degrees, 21 minutes, 11 seconds N., Longitude 116 degrees, 23 minutes, 08 seconds W.; NAD 83; USGS St. Joe Baldy quadrangle.
RANGE IN CHARACTERISTICS:
Depth to bedrock - more than 60 inches
Solum thickness - 26 to 44 inches
Moisture control section - dry, August to September (20 to 40 days), moist, September through July
Average annual soil temperature - 43 to 47 degrees F.
Average summer soil temperature - 47 to 56 degrees F with an O horizon
Volcanic ash mantle - 14 to 24 inches thick
Volcanic glass content in the 0.02 to 2 mm fraction - 30 to 65 percent
Acid-oxalate extractable Al + 1/2 Fe - 1.0 to 3.0 percent
Phosphate retention - 55 to 90 percent
15 bar water retention on air dried samples - 7 to 12 percent
A horizon
Value - 4 through 6 dry, 2 through 4 moist
Chroma - 2 or 3 dry or moist
Texture - GR-ASHY-SIL, GR-ASHY-L or ASHY-SIL
Rock fragment content - 5 to 30 percent
Bulk density - 0.65 to 0.85 g/cc
Clay content 3 to 8 percent
Reaction - moderately acid to neutral
Bw horizon
Hue - 10YR or 7.5YR
Value - 5 through 7 dry, 3 through 5 moist
Texture - CBV-ASHY-SIL, CBV-ASHY-L, GRV-ASHY-SIL or GRV-ASHY-L; Bw1 (if present), may range to GRASHY-SIL, or CB-ASHY-SIL
Rock fragment content 35 to 60 percent; Bw1 (if present) may range 25 to 35 percent
Bulk density - 0.65 to 0.85 g/cc
Clay content 3 to 8 percent
Reaction - moderately acid to neutral
2Bw horizon (2BC horizon if present)
Hue - 10YR or 7.5YR
Value - 6 or 7 dry, 4 or 5 moist
Texture - CBX-SIL, CBX-L, CBV-L, CBV-SIL, GRV-SIL, GRV-L, GRX-L
Rock fragment content - 35 to 80 percent
Clay content 3 to 8 percent
Reaction - moderately acid to neutral
2C horizon
Hue - 10YR or 7.5YR
Value - 6 or 7 dry, 4 to 6 moist
Chroma - 3 through 6, dry or moist
Texture - CBX-L, STX-L, CBX-SIL, STX-SIL, GRX-L, GRX-SIL
Rock fragment content - 65 to 90 percent
Clay content 3 to 8 percent
Reaction - strongly acid to slightly acid
COMPETING SERIES: This is the
Harl and
Lakefork (T) series.
Harl soils: have buried horizons with 10 to 18 percent clay in the loamy-skeletal part; pscs dominated by rock fragments of basalt origin; and formed in ash over colluvium from basalt.
Lakefork soils: rock fragments in pscs are subrounded or rounded; formed in volcanic ash over till from basalt, metasedimentary and metavolcanic rocks mixed with granitic rocks.
Similar soils with glassy mineralogy
Dorb 40 to 60 inches to hard fractured basalt; upper part of the pscs has glassy mineralogy, formed in volcanic ash over colluvium from basalt
GEOGRAPHIC SETTING: Ahrs soils are on all aspects of mountains at lower elevations, but mainly occupy southerly aspects at high elevations. Slopes range from 15 to 75 percent. These soils formed in material weathered from metasedimentary rocks such as siltite and argillite, with a mantle of volcanic ash and loess. Elevations range from 2,200 to 4,800 feet. The average annual air temperature ranges from 42 to 46 degrees F. and average annual precipitation is 30 to 42 inches. The average frost-free period is from 90 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Honeyjones, Latour, Lotuspoint, Pinecreek, and Tigley soils. The Honeyjones soils have less than 35 percent coarse fragments in the ash mantle and are on cooler, north-facing slopes. The Tigley soils are on adjacent foothills and have argillic horizons. The Latour soils are cryic and are located at higher elevations. The Lotuspoint soils are mesic and are on south-facing ridges. The Pinecreek soils are on south-facing mountain slopes and have umbric epipedons.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderate permeability.
USE AND VEGETATION: These soils are used for timber production, livestock grazing, wildlife habitat, recreation, and watershed. Potential natural vegetation is mainly grand fir, Douglas-fir, western white pine, and western larch, with an understory of Columbia brome, common snowberry, creambush oceanspray, goldthread, myrtle pachystima, longtube twinflower, starry false-Solomons-seal, queencup beadlily, piper anemone, sedge, and American trailplant.
DISTRIBUTION AND EXTENT: This soil is moderately extensive. MLRA 43A.
MLRA OFFICE RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: St. Joe Area, Shoshone County, Idaho, 1993.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 2 to 8 inches (A horizon)
Cambic horizon - the zone from 8 to 32 inches (Bw1 and 2Bw2 horizons)
Volcanic ash mantle - the zone from 2 to 20 inches (A and Bw1 horizons)
Particle-size control section - the zone from 2 to 42 inches (A, Bw1, 2Bw2 and part of the 2C1 horizons)
ADDITIONAL DATA: Laboratory data available for Soil Survey Sample Number: 89ID079003, NSSL Pedon Number: 89P0747, Shoshone County, Idaho.