LOCATION PEARSONCREEK IDEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Andic Dystrudepts
TYPICAL PEDON: Pearsoncreek ashy loam, open-burned, woodland; on a west-facing slope of 30 percent at 3,800 feet elevation. When described on July 13, 1994, the soil was slightly moist throughout. (Colors are for dry soil unless otherwise stated.)
Oi--0 to 0.5 inch; needles, leaves and twigs. (0.5 to 1 inch thick)
Oe--0.5 to 2 inches; decomposed organic matter mixed with Mt. St. Helens volcanic ash. (0.5 to 1.5 inches thick)
A--2 to 3 inches; grayish brown (10YR 5/2) ashy loam, very dark grayish brown (10YR 3/2) moist; weak very fine granular structure; soft, very friable, nonsticky and slightly plastic; many very fine roots; many very fine tubular pores; slightly acid (pH 6.5); abrupt wavy boundary. (1 to 2 inches thick)
Bw1--3 to 9 inches; yellowish brown (10YR 5/4) ashy loam, dark yellowish brown (10YR 4/4) moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and slightly plastic; many very fine, few fine, medium and coarse roots; many very fine tubular pores; slightly acid (pH 6.5); clear wavy boundary. (3 to 8 inches thick)
Bw2--9 to 12 inches; light yellowish brown (10YR 6/4) ashy loam, dark yellowish brown (10YR 4/4) moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and slightly plastic; many very fine, few fine, medium and coarse roots; common very fine tubular pores; 5 percent gravel; neutral (pH 6.8); clear wavy boundary. (3 to 5 inches thick)
2Bw3--12 to 17 inches; light yellowish brown (10YR 6/4) gravelly sandy 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, few fine roots; common very fine tubular pores; 10 percent gravel, 5 percent cobbles; slightly acid (pH 6.5); clear wavy boundary. (5 to 12 inches thick)
2BC--17 to 29 inches; very pale brown (10YR 7/4) very cobbly sandy loam, yellowish brown (10YR 5/4) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; common very fine tubular and irregular pores; 15 percent gravel, 30 percent cobbles; slightly acid (pH 6.5); gradual wavy boundary. (0 to 20 inches thick)
2C1--29 to 50 inches; very pale brown (10YR 7/3) very cobbly sandy loam, mixed yellowish brown (10YR 5/4) and brown (10YR 5/3) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; common very fine tubular and irregular pores; 30 percent gravel, 20 percent cobbles; slightly acid (pH 6.5); clear wavy boundary. (16 to 26 inches thick)
2C2--50 to 60 inches; pale yellow (2.5Y 7/3) very cobbly sandy loam, light olive brown (2.5Y 5/3) moist; massive; hard, firm, slightly sticky and slightly plastic; few fine roots; common very fine, few fine tubular pores; few faint silica coatings that are light yellowish brown (2.5Y 6/3) moist; 30 percent gravel, 20 percent cobbles; slightly acid (pH 6.3).
TYPE LOCATION: Boundary County, Idaho; about 5.75 miles northwest of Naples, about 2200 feet north and 2300 feet east of the southwest corner of sec. 31, T. 61 N., R. 1 W; Latitude - 48 degrees, 35 minutes, 45 seconds North; Longitude - 116 degrees, 31 minutes, 00 seconds West.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 44 to 46 degrees F.
Average summer soil temperature - 54 to 56 degrees F. with an O horizon
Moisture control section - dry 30 to 45 days (August to September), moist mid-September through July; udic moisture regime
Solum thickness - 20 to 34 inches
Surface stones and boulders - 0 to 3 percent
Volcanic ash mantle - 10 to 13 inches thick
Volcanic glass content - 30 to 65 percent
Acid-oxalate extr. Al + 1/2 Fe - 1.0 to 3.0 percent
Phosphate retention - 55 to 90 percent
A horizon
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Texture - ASHY-L, ASHY-SIL, GR-ASHY-SIL
Clay content - 3 to 10 percent
Gravel content - 0 to 20 percent
Bulk density - 0.65 to 1.00 grams per cubic centimeter
Reaction - moderately acid to neutral
Bw horizons
Hue - 10YR or 7.5YR
Value - 5 or 6 dry, 3 or 4 moist
Texture - ASHY-L, ASHY-SIL, GR-ASHY-SIL
Clay content - 3 to 10 percent
Gravel content - 0 to 20 percent
Bulk density - 0.65 to 1.00 grams per cubic centimeter
Reaction - slightly acid or neutral
2Bw horizon
Hue - 10YR or 2.5Y
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 3 to 6 dry or moist
Texture - GR-SL, SL, CBV-SL, STV-SL, GRV-SL
Clay content - 3 to 10 percent
Gravel content - 5 to 25 percent
Cobble content - 5 to 30 percent
Stone content - 0 to 30 percent
Reaction - moderately acid to neutral
2BC horizon
Hue - 10YR or 2.5Y
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 3 or 4 dry or moist
Texture - CBV-SL, GRV-SL, STV-SL
Clay content - 3 to 10 percent
Gravel content - 10 to 30 percent
Cobble content - 5 to 30 percent
Stone content - 0 to 30 percent
Reaction - moderately acid or slightly acid
2C horizon
Hue - 10YR or 2.5Y
Value - 6 to 8 dry, 4 to 6 moist
Chroma - 2 to 4 dry or moist
Texture - GRV-SL, CBV-SL, STV-SL, BYV-SL, STX-SL
Clay content - 3 to 10 percent
Gravel content - 10 to 30 percent
Cobble content - 10 to 30 percent
Stone and boulder content - 0 to 30 percent
Reaction - moderately acid or slightly acid
COMPETING SERIES: These are the Backroad, Hoffstadt, and Tinker series. Backroad soils have 2E and 2E/Bw horizons. Hoffstadt soils have a lithic conatct at 40 to 60 inches. Tinker soils have very cobbly loam in the A and Bw horizons.
GEOGRAPHIC SETTING: Pearsoncreek soils are mostly on south and west-facing mountain and foothill slopes. Slopes range from 5 to 65 percent. They formed in glacial till derived from granite, gneiss, and schist rocks with a thin mantle of volcanic ash. Elevations range from 2,800 to 4,800 feet. The average annual air temperature is 43 to 46 degrees F. and average annual precipitation is 30 to 45 inches. The average frost-free period is 90 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Idamont, Pend Oreille, and Treble soils. Idamont soils are on east-facing mountain slopes and have a volcanic ash mantle more than 14 inches thick and are ashy over loamy in the control section. Pend Oreille soils are on north-facing mountain slopes and have a volcanic ash mantle more than 14 inches thick and are ashy over loamy in the control section. Treble soils are on south-facing mountain slopes and do not have a volcanic ash mantle and are dry more than 45 consecutive days in the soil moisture control section.
DRAINAGE AND PERMEABILITY: Well drained; medium to very rapid runoff; permeability is moderate in the upper part and moderate to moderately rapid below.
USE AND VEGETATION: These soils are used for woodland timber production, wildlife habitat, recreation, and watershed. Potential natural vegetation is mainly grand fir, western white pine, western larch, Douglas-fir, and lodgepole pine with an understory of Rocky Mountain maple, darkwoods violet, starry false Solomons seal, woods rose, common princes pine, dampwoods blueberry, longtube twinflower, myrtle pachystima, and queencup beadlily.
DISTRIBUTION AND EXTENT: Northern Idaho, and possibly northwestern Montana, and northeastern Washington. This series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Boundary County, Idaho, 2002.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the mineral soil surface to 7 inches (A and part of Bw1 horizon)
Cambic horizon - the zone from 3 to 17 inches (Bw1, Bw2, 2Bw3 horizons)
Volcanic ash mantle - the zone from 2 to 12 inches (A, Bw1, Bw2 horizons)
Particle-size control section - the zone from 10 to 40 inches (2Bw3, 2BC, and part of the 2C1 horizon)