LOCATION DWORSHAK IDEstablished Series
TAXONOMIC CLASS: Ashy over loamy, amorphic over mixed, superactive, frigid Alfic Udivitrands
TYPICAL PEDON: Dworshak ashy silt loam - on a southeast facing convex slope of 15 percent at an elevation of 3,500 feet, forested. (Colors are for dry soil unless otherwise noted. When described on September 6, 1979, the profile was moist throughout.)
Oi--0 to 1.5 inch; fresh and partially decomposed needles, leaves, twigs, and moss.
Oe--1.5 to 3 inches; decomposed needles, leaves, moss, and twigs.
A--3 to 11 inches; yellowish brown (10YR 5/6) ashy silt loam, dark brown (7.5YR 3/4) moist; weak medium subangular blocky structure parting to weak fine granular; soft, very friable, nonsticky and nonplastic; many very fine, fine, medium and coarse roots; many very fine irregular pores; slightly acid (pH 6.4); gradual smooth boundary. (6 to 10 inches thick)
Bw--11 to 18 inches; yellowish brown (10YR 5/6) ashy silt loam, brown (7.5YR 4/4) moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine, fine, and coarse roots; many very fine irregular pores; slightly acid (pH 6.2) abrupt wavy boundary. (5 to 9 inches thick)
2E/Bt--18 to 31 inches; E - very pale brown (10YR 7/4) silt loam, brown (7.5YR 5/4) moist; B - light yellowish brown (10YR 6/4), brown (7.5YR 4/4) moist; weak fine and medium prismatic structure parting to moderate fine and medium subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common very fine and many fine and medium roots; many very fine and fine irregular and few very fine tubular pores; few faint clay films lining pores and on faces of peds; 10 percent gravel; slightly acid (pH 6.2); clear wavy boundary. (11 to 16 inches thick)
3Bt/E--31 to 50 inches; B - light brown (7.5YR 6/4) gravelly clay loam, brown (7.5YR 4/4) moist; E - very pale brown (10YR 7/4), brown (7.5YR 5/4) moist; moderate fine and medium prismatic structure parting to moderate fine and medium subangular blocky; hard, firm, moderately sticky and moderately plastic; common very fine and many fine and medium roots; many very fine and fine irregular and few fine tubular pores; common faint and distinct clay films lining pores and on faces of peds; tongues of very pale brown (10YR 7/4) material 1 to 2 inches wide and 3 inches apart; 20 percent gravel; moderately acid (pH 6.0); gradual wavy boundary. (15 to 26 inches thick)
3Bt--50 to 63 inches; reddish yellow (7.5YR 6/6) very gravelly clay loam, strong brown (7.5YR 5/6) moist; moderate medium and coarse prismatic structure; hard, firm, moderately sticky and moderately plastic; few fine roots; many very fine irregular and common very fine and fine tubular pores; many distinct clay films lining pores and on faces of peds; common organic stains; 30 percent gravel and 15 percent cobbles; strongly acid (pH 5.2).
TYPE LOCATION: Clearwater County, Idaho; about 2.5 miles northeast of Cavendish, Idaho; about 2,300 feet north and 1,800 feet west of the southeast corner of sec. 31, T. 38 N., R. 1 E.; Latitude - 46 degrees, 35 minutes, 30 seconds North; Longitude - 116 degrees, 22 minutes, 40 seconds West. USGS Southwick Quadrangle.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 39 to 45 degrees F. Frigid temperature regime.
Soil moisture control section - dry for 20 to 45 consecutive days in late summer and early fall. Udic moisture regime.
Base saturation - 35 to 60 percent in the argillic horizon.
Thickness of volcanic ash mantle - 14 to 20 inches.
Volcanic glass content in the 0.02 to 2.0mm fraction - 15 to 50 percent.
Acid-oxalate extractable Al plus 1/2 Fe - 1.5 to 2.7 percent.
Phosphate retention - 55 to 95 percent.
15-bar water retention on air dried samples - 8 to 12 percent.
A and Bw horizons
Hue - 10YR or 7.5YR
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 2 to 6 dry, 2 to 4 moist
Texture - ASHY-SIL, ASHY-L
Clay content - 8 to 10 percent
Rock fragments - 0 to 1 percent gravel
Reaction - moderately acid to neutral
Bulk density - 0.65 to 1.00 g/cc
2E horizon (present in some pedons)
Hue - 7.5YR or 10YR dry
Value - 3 or 4 moist
Clay content - 18 to 20 percent
2E/Bt or 2Bt/E horizons
E part
Hue - 10YR or 7.5YR moist
Value - 6 or 7 dry, 3 to 5 moist
Chroma - 3 or 4 moist
Clay content - 16 to 20 percent
B part
Hue - 10YR or 7.5YR
Value - 3 to 5 moist
Chroma - 3 or 4 moist
Texture - SIL, GR-SIL, GR-CL
Clay content - 21 to 27 percent
Rock fragments - 0 to 25 percent gravel
Reaction - strongly acid to neutral
2Bt horizon (present in some pedons)
Hue - 5YR to 10YR moist
Value - 3 to 6 moist
Chroma - 3 or 4 moist
Texture - SIL, L, CL, GR-L
Clay content - 15 to 29 percent
Rock fragments - 0 to 10 percent gravel
Reaction - slightly acid or neutral
3Bt horizon
Hue - 2.5YR to 10YR
Value - 3 to 7 dry, 3 to 5 moist
Chroma - 3 to 8 dry, 3 to 6 moist
Texture - GR-CL, GRV-CL, GR-L STX-SIL
Clay content - 18 to 34 percent
Coarse fragments - 0 to 60 percent gravel, 0 to 25 percent cobbles, 15 to 80 percent total rock fragments
Mica Content - 3 to 10 percent
Reaction - very strongly acid to slightly acid
COMPETING SERIES: These are the Brodeer, Cranberry, Helmer, and Scand series. Brodeer soils do not have 3Bt horizons. Cranberry soils have less than 10 percent rock fragments in the 3Bt horizons. Helmer soils are shallow to a fragipan. Scand soils have 30 to 85 percent mica flakes in the 3Bt, 3BC, and 3C horizons.
GEOGRAPHIC SETTING: Dworshak soils are on mountain slopes at elevations of 1,600 to 4,500 feet and have slopes of 5 to 50 percent. These soils formed in volcanic ash and loess over residuum from metamorphic rock. The average annual temperature is 38 to 44 degrees F. The average annual precipitation is 28 to 55 inches and the frost-free season is 50 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Crumarine, Kauder, Kruse, Hugus, and Teakean soils. Crumarine soils are on narrow valley floors and are somewhat poorly drained. Kauder soils are on foothills and have a fragipan. Kruse soils are on mountains and foothills and have loam subsoils and loamy sand substratums. Hugus soils are on mountains and are loamy-skeletal. Teakean soils are on mountains, are deep to a fragipan and have a xeric moisture regime.
DRAINAGE AND PERMEABILITY: Well drained; runoff is rapid; permeability is moderately slow.
USE AND VEGETATION: This soil is used mainly for timber production, livestock grazing, wildlife habitat and watershed. The natural vegetation is mainly western redcedar, grand fir, Douglas-fir, western larch, Pacific yew, common snowberry, strawberry, common princes pine, sweetscented bedstraw, Myrtle pachystima, western rattlesnake plantain, and longtube twinflower.
DISTRIBUTION AND EXTENT: North-central Idaho; Dworshak soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Clearwater County, Idaho, 2003.
REMARKS: The classification was changed from Fine-loamy, mixed Andeptic Cryoboralfs to Ashy over fine-loamy, mixed, frigid Alfic Udivitrands in 1994.
Classification was changed to Ashy over loamy, amorphic over mixed, superactive, frigid Alfic Udivitrands in 1998.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 3 to 11 inches (A horizon).
Cambic horizon - The zone from 11 to 18 inches (Bw horizon).
Volcanic ash mantle - The zone from 3 to 18 inches (A and Bw horizons).
Argillic horizon - The zone from 31 to 63 inches (2B/E, and 3Bt horizon).
Particle-size control section - The zone from 3 to 43 inches (A, Bw, 2E/Bt, and part of the 2Bt/E horizons).
The ranges in values listed in the range in characteristics for volcanic glass content, acid oxalate extractable Al+1/2 Fe, phosphate retention, 15 bar water retention, and bulk density are estimates only.