LOCATION THREEBEAR ID
Established Series
Rev. GAH/BDG/EMM
07/2013
THREEBEAR SERIES
The Threebear series consists of moderately deep to a fragipan, moderately well drained soils formed in loess and reworked loess with a thick mantle of volcanic ash. They are mountain slopes, structural benches, and hills on plateaus. Saturated hydraulic conductivity is low and slopes range from 3 to 40 percent. The average annual precipitation is about 36 inches and the average annual temperature is about 42 degrees F.
TAXONOMIC CLASS: Medial over loamy, amorphic over mixed, superactive, frigid Oxyaquic Udivitrands
TYPICAL PEDON: Threebear medial silt loam, forested on a 22 percent slope at 2,930 feet elevation. Aspect is northeast. (Colors are for dry soil unless otherwise noted)
Oi--0 to 1 inch; slightly decomposed needles and twigs. (1 to 3 inches thick)
A--1 to 3 inches; yellowish brown (10YR 5/4) medial silt loam, dark yellowish brown (10YR 3/4) moist; weak medium granular structure; soft, very friable, nonsticky and slightly plastic; common fine, and very fine and few medium roots; few very fine tubular pores; slightly acid (pH 6.4) clear smooth boundary. (1 to 8 inches thick)
Bw1--3 to 10 inches; yellowish brown (10YR 5/4) medial silt loam, dark yellowish brown (10YR 4/4) moist; weak coarse subangular blocky structure; soft, very friable, nonsticky and slightly plastic; common fine and very fine, and few medium and coarse roots; few very fine tubular pores; slightly acid (pH 6.2); gradual smooth boundary.
Bw2--10 to 18 inches; light yellowish brown (10YR 6/4) medial silt loam, dark yellowish brown (10YR 4/4) moist; weak coarse subangular blocky structure; soft, very friable, nonsticky and slightly plastic; common fine and very fine and few medium and coarse roots; few very fine tubular pores; moderately acid (pH 6.0); abrupt wavy boundary. (Bw horizons 10 to 19 inches thick)
2E/Bt--18 to 26 inches; 90 percent very pale brown (10YR 7/3) silt loam, yellowish brown (10YR 5/4) moist; 10 percent light yellowish brown (10YR 6/4), dark yellowish brown (10YR 4/4) moist; weak medium and coarse subangular blocky structure; soft and slightly hard, friable, slightly sticky and slightly plastic; few fine and very fine roots throughout and between peds, few medium roots between peds; many very fine tubular and few fine irregular pores; few faint patchy clay films on faces of peds; very strongly acid (pH 5.0); gradual wavy boundary. (4 to 18 inches thick)
2Bt/E1--26 to 35 inches; 60 percent light yellowish brown (10YR 6/4) silt loam, dark yellowish brown (10YR 4/4) moist; 40 percent very pale brown (10YR 7/3), yellowish brown (10YR 5/4) moist; moderate medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine and medium roots along faces of peds; many very fine tubular and few fine irregular pores; common faint patchy clay films on faces of peds and in pores; very strongly acid (pH 4.8); clear wavy boundary.
2Bt/E2--35 to 40 inches; 75 percent light yellowish brown (10YR 6/4) silt loam, yellowish brown (10YR 5/4) moist; 25 percent very pale brown (10YR 7/3), yellowish brown (10YR 5/4) moist; moderate coarse prismatic structure; very hard (B) and soft (E), very firm (B) and friable (E), slightly sticky and slightly plastic; few fine and very fine roots along faces of peds; common very fine tubular pores; common faint and few distinct discontinuous clay films on faces of peds and in pores; very strongly acid (pH 5.0); gradual wavy boundary. (2Bt/E horizons 0 to 20 inches thick)
2Btxb1--40 to 55 inches; light yellowish brown (10YR 6/4) silt loam, dark yellowish brown (10YR 4/6) moist; strong very coarse prismatic structure; very hard, very firm and brittle, slightly sticky and moderately plastic; few fine and very fine roots between peds; common very fine tubular pores; common distinct dark yellowish brown (10YR 4/6) clay films on faces of peds; E material is between prism faces, 10 to 20 mm thick near upper boundary; few patchy prominent black (10YR 2/1) manganese stains on faces of peds; very strongly acid (pH 5.0); clear wavy boundary. (8 to 21 inches thick)
2Btxb2--55 to 69 inches; light yellowish brown (10YR 6/4) silty clay loam, dark yellowish brown (10YR 4/6) moist; moderate coarse and very coarse prismatic structure; very hard, firm and brittle, slightly sticky and moderately plastic; common very fine tubular pores; common distinct dark yellowish brown (10YR 4/6) clay films on faces of peds; few rounded medium soft masses of iron; very strongly acid (pH 4.8)
TYPE LOCATION: Latah County, Idaho, about 10 miles north of Ahsahka, Idaho; about 80 feet south and 110 feet west of the northeast corner of section 9, T. 38 N., R. 1 E. Latitude - 46 degrees, 39 minutes, 24 seconds North; Longitude - 116 degrees, 19 minutes, 46 seconds West. USGS Aldermand Ridge Quadrangle.
RANGE IN CHARACTERISTICS:
Depth to fragipan - 23 to 40 inches
Depth to argillic horizon - 15 to 36 inches
Average annual soil temperature - 39 to 45 degrees F. (Frigid temperature regime)
Soil moisture regime - usually moist year round and not dry for 30 consecutive days during June to October. (Udic soil moisture regime)
Thickness of volcanic ash mantle - 14 to 23 inches
Volcanic glass content - 15 to 50 percent
Acid-oxalate extractable Al + 1/2 Fe - 1.0 to 2.7 percent
15 bar water retention - weighted average for all horizons with andic soil properties range from 12 to 17 percent
Phosphate retention - 55 to 95 percent
A horizon
Hue - 7.5YR or 10YR dry or moist
Value - 3 to 5 dry, 2 to 4 moist
Chroma - 2 to 4 dry or moist
Clay content - 3 to 15 percent
Reaction - moderately acid or slightly acid
Moist bulk density - 0.65 to 0.85 g/cc
Bw horizons
Hue - 7.5YR or 10YR dry or moist
Value 4 to 6 dry, 3 or 4 moist
Chroma - 3 to 6 dry, 2 to 4 moist
Clay content - 3 to 15 percent
Reaction - moderately acid or slightly acid
Moist bulk density - 0.65 to 0.90 g/cc
2E/Bt horizon
E part
Hue - 7.5YR or 10YR dry or moist
Value - 6 to 8 dry, 4 to 6 moist
Chroma - 2 to 4 dry or moist
Clay content - 10 to 22 percent
B part
Hue - 7.5YR or 10YR dry or moist
Value - 5 or 6 dry
Chroma - 4 to 6 dry or moist
Clay content - 15 to 25 percent
Reaction very strongly acid to slightly acid
2Bt/E horizons
B part
Hue - 7.5YR or 10YR dry or moist
Value - 5 or 6 dry, 4 or 5 moist
Chroma - 2 to 6 dry, 3 or 4 moist
Texture - silt loam or silty clay loam
Clay content - 21 to 28 percent
E part
Hue - 7.5YR or 10YR dry or moist
Value - 5 to 7 dry, 3 to 6 moist
Chroma - 2 to 4 dry or moist
Texture - silt loam or silty clay loam
Clay content - 18 to 28 percent
Reaction - extremely acid to moderately acid
2Btx/E horizons present in some pedons
B part
Hue - 10YR or 7.5YR
Value - 5 or 6 dry
Chroma - 3 or 4 dry or moist
Texture - silt loam
Clay content - 16 to 22 percent
E part
Value - 7 or 8 dry, 5 or 6 moist
Chroma - 2 or 3 dry or moist
Texture - silt loam
Clay content - 10 to 20 percent
Reaction - very strongly acid to moderately acid
2Btxb horizons
Hue - 7.5YR or 10YR dry or moist
Value - 4 to 7 dry, 3 to 6 moist
Chroma - 3 to 6 dry, 2 to 6 moist
Textures - silt loam, silty clay loam, sandy clay loam or loam
Clay content - 21 to 32 percent
Reaction - extremely acid to strongly acid
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Threebear soils are on mountain slopes, structural benches, and hills on plateaus at elevations of 1,600 to 4,000 feet 488 to 1220 meters) with slopes of 3 to 40 percent. These soils formed in loess and reworked loess with a thick mantle of volcanic ash. The average annual temperature is 38 to 46 degrees F. and the average annual precipitation is 25 to 50 inches (635 to 1270 mm). The frost free season is 50 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Dworshak,
Elkridge,
Norwidge and
Riswold soils. Dworshak soils are on mountains and hills and lack a fragipan. Elkridge and Riswold soils are on hills and canyons and lack a fragipan. Norwidge soils are on hills and lack a fragipan.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Moderately well drained; medium runoff; low saturated hydraulic conductivity. A perched water table is present. Typically it occurs at a depth of 19 to 40 inches from December through May but can occur at a depth of 4 to 40 inches from November through July.
USE AND VEGETATION: These soils are used for timber production, wildlife habitat and watershed. Potential natural vegetation is western hemlock, western redcedar, grand fir, Douglas-fir, western larch, and western white pine with an understory of queencup beadlily, longtube twinflower, oneleaf foam flower, goldthread, starry false Solomons-seal, myrtle pachystima, common snowberry and Columbia brome.
DISTRIBUTION AND EXTENT: North central Idaho; Threebear soils are moderately extensive. MLRA 43A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Clearwater County, Idaho, 2003.
REMARKS: Diagnostic horizons and other features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 3 inches (Oi and A horizons)
Volcanic ash mantle - The zone from 1 to 18 inches (A, Bw1, and Bw2 horizons)
Cambic horizon - The zone from 3 to 18 inches (Bw1 and Bw2 horizons)
Argillic horizon - The zone from 26 to 69 inches (2Bt/E1, 2Bt/E2, 2Btxb1 and 2Btxb2 horizons)
Meets Alfic subgroup criteria based on the presence of an argillic horizon.
Particle size control section - The zone from 1 to 41 inches (A, Bw1, Bw2, 2E/Bt, 2Bt/E1, 2Bt/E2, and portions of the 2Btxb1 horizons)
Classification change on 1/2010 from Alfic to Oxyaquic Udivitrands based on the seasonally perched water table and criteria in the Tenth Edition of Soil Taxonomy.
The ranges of values listed under the Range in Characteristics for the soil properties Volcanic glass content, Acid-oxalate Al +1/2 Fe, Phosphate retention and 15-bar water retention are estimates only.
Additional data: This series has laboratory data S95-ID-035-011 (96P28) Clearwater County, Idaho; S99-ID-035-001 (99P0119) Clearwater County, Idaho; and S07ID057006 (07N0663) Latah County, Idaho; by NSSL, Lincoln, NE.
National Cooperative Soil Survey
U.S.A.