LOCATION LONGPEN ID
Established Series
Rev. BLR-GH-EMM
07/2013
LONGPEN SERIES
The Longpen series consists of very deep, well drained soils that formed in loess over colluvium weathered from basalt with an admixture of volcanic ash on the surface. Longpen soils are on canyon sides and structural benches and have slopes of 5 to 50 percent. Permeability is slow. The average annual precipitation is about 32 inches and the average annual air temperature is about 43 degrees F.
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Vitrandic Haploxeralfs
TYPICAL PEDON: Longpen ashy silt loam, on a 40 percent canyon side at 2,700 feet elevation on a south aspect. (When described on November 11, 1982 the soil was dry below 12 inches; colors are for dry soil unless otherwise noted).
Oi--0 to 2 inches; undecomposed leaves, twigs and needles.
A1--2 to 6 inches; brown (10YR 4/3) ashy silt loam, dark brown (7.5YR 3/2) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine, fine and medium tubular pores; 5 percent paragravel; slightly acid (pH 6.3); clear smooth boundary.
A2--6 to 9 inches; dark yellowish brown (10YR 4/4) ashy silt loam, dark yellowish brown (10YR 3/4) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine, and common medium roots; many very fine, fine and medium tubular pores; slightly acid (pH 6.3); clear wavy boundary. (Combined thickness of A horizons - 2 to 8 inches)
BtA--9 to 18 inches; yellowish brown (10YR 5/4) silt loam, dark yellowish brown (10YR 3/4) moist; moderate medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; many medium and common very fine and fine roots; many very fine and common fine tubular pores; common faint clay films lining pores and on faces of peds; slightly acid (pH 6.1); clear smooth boundary. (0 to 10 inches thick)
Bt1--18 to 28 inches; brown (7.5YR 5/4) silt loam, dark yellowish brown (10YR 3/4) moist; moderate medium and coarse subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common fine, medium and coarse roots; common very fine and fine tubular pores; common faint clay films lining pores and on faces of peds; common clean silt coatings of faces of peds; slightly acid (pH 6.1); gradual smooth boundary.
Bt2--28 to 49 inches; brown (7.5YR 5/4) silt loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; hard, firm, moderately sticky and moderately plastic; common fine, medium and coarse roots; common very fine and fine tubular pores; common faint clay films lining pores and on faces of peds; common clean silt coatings on faces of peds; moderately acid (pH 5.9); clear smooth boundary. (Combined thickness of Bt horizons 13 to 40 inches thick)
2Btb1--49 to 65 inches; brown (7.5YR 5/4) silty clay loam, dark brown (7.5YR 3/3) moist; moderate medium subangular blocky structure; very hard, very firm, very sticky and very plastic; common fine and medium roots; few very fine tubular pores; common faint clay films in pores and on faces of peds; common clean silt coatings on faces of peds; moderately acid (pH 5.8); clear smooth boundary. (8 to 25 inches thick)
2Btb2--65 to 71 inches; brown (7.5YR 4/4) silty clay loam, dark brown (7.5YR 3/4) moist; moderate medium and coarse subangular blocky structure; hard, firm, very sticky and very plastic; common very fine and few fine tubular pores; common faint clay films in pores and on faces of peds; moderately acid (pH 5.6).
TYPE LOCATION: Clearwater County, Idaho; about 6 miles north of Orofino, Idaho; about 900 feet north and 1,600 feet east of the southwest corner of section 4, T.37N., R.2E.; Latitude - 46 degrees, 34 minutes, 31 seconds North; Longitude - 116 degrees, 12 minutes, 48 seconds West; USGS Dent Quadrangle.
RANGE IN CHARACTERISTICS:
Soil temperature is 41 to 46 degrees F.
Frigid temperature regime
Soil moisture - moist in the fall through early summer, usually dry for 45 to 60 consecutive days, mid-July through mid-September
Xeric moisture regime
A horizons
Hue - 10YR or 7.5YR
Value - 4 to 6 dry, 2 to 4 moist
Chroma - 2 to 4 dry or moist
Texture - ashy silt loam or loam
Clay content - 10 to 25 percent
Reaction - slightly acid or neutral
Rock fragments - 0 to 5 percent gravel
Acid oxalate extractable Al + 1/2Fe - 0.4 to 1.0 percent
Volcanic glass content - 5 to 10 percent
AB horizons (where present)
Hue - 7.5YR or 10YR
Value - 4 to 6 dry, 3 or 4 moist
Chroma - 3 or 4 dry or moist
Clay content - 14 to 25 percent
Rock fragment content - 0 to 5 percent gravel
Bt horizons
Hue - 10YR or 7.5YR
Value - 4 to 6 dry, 3 or 4 moist
Chroma - 4 to 6 dry, 2 to 4 moist
Textures - silt loam or silty clay loam
Clay content - 20 to 32 percent
Base saturation (sum of cations) - 50 to 60 percent
Reaction - moderately acid to neutral
Rock fragments - 0 to 5 percent gravel and 0 to 3 percent cobbles
2Btb horizons
Hue - 7.5YR or 10YR
Value - 4 or 5 dry, 3 or 4 moist
Chroma - 4 to 6 dry, 3 or 4 moist
Textures - silty clay loam, silty clay, clay loam or clay
Percent clay - 27 to 41 percent
Reaction - strongly acid to slightly acid
Rock fragments - 0 to 15 percent gravel and 0 to 3 percent cobbles
COMPETING SERIES:
Talmaks soils - have EB and BE horizons above the Bt horizon
Sinkler - have Btxb horizons
GEOGRAPHIC SETTING: Longpen soils are on canyon sides and structural benches and have slopes of 5 to 50 percent. These soils formed in loess colluvium weathered from basalt with an admixture of volcanic ash. Elevation is 1,100 to 3,400 feet. The average annual temperature ranges from 40 to 45 degrees F. The average annual precipitation ranges from 24 to 40 inches and the frost free season is 80 to 125 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Agatha,
Klickson, and
Setters soils. Agatha and Klickson soils are on canyon sides and are loamy-skeletal. Setters soils are on benches and have a fine textured control section.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is medium to rapid. Permeability is slow.
USE AND VEGETATION: This soil is used mainly for timber production, livestock grazing, wildlife habitat and watershed. The natural vegetation is grand fir, Douglas-fir and ponderosa pine with an understory of mallow ninebark common snowberry, creambush oceanspray, rose and Rocky Mountain maple.
DISTRIBUTION AND EXTENT: North-central Idaho; Longpen soils are not extensive. MLRA 43A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Clearwater County, Idaho, 2003.
REMARKS: Mass failures are common on this soil. The slowly permeable lower part of the soil causes lateral subsurface flow.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 9 inches (Oi, A1 and A2 horizons).
Argillic horizon - The zone from 9 to 71 inches (BtA, Bt1, Bt2, BE, 2Btb1, and 2Btb2 horizons).
Particle size control section - The zone from 9 to 29 inches (BtA, Bt1 and part of the Bt2 horizon).
The ranges listed under the A horizons for volcanic glass content and acid-oxalate extractable Fe + 1/2 Fe are estimates only.
ADDITIONAL DATA: Partial laboratory data is available for another pedon of Longpen. Soil Survey Sample No. - S92ID-035-034. Pedon No. - 93P 89.
National Cooperative Soil Survey
U.S.A.