LOCATION KOOSKIA IDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Xeric Argialbolls
TYPICAL PEDON: Kooskia silt loam, forested. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 0.3 inches; slightly decomposed needles, leaves, and cones; strongly acid (pH 5.2); abrupt wavy boundary. (0 to 2 inches thick)
A1--0.3 to 4 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak very fine subangular blocky structure parting to strong fine, very fine, and medium granular; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine pores; few worm channels and casts; few uncoated silt grains; few dark reddish brown and yellowish red soft concretions less than 1 mm. in diameter; moderately acid (pH 6.0); clear wavy boundary. (2 to 8 inches thick)
A2--4 to 9 inches; dark grayish brown (10YR 4/2) (brown, 10YR 5/3 rubbed) silt loam, very dark brown (7.5YR 2/2) moist; weak medium subangular blocky structure parting to moderate medium and coarse granular; slightly hard, friable, slightly sticky and slightly plastic; few coarse roots; many very fine and few fine pores; few worm channels and casts; few uncoated silt grains; few reddish brown and black soft concretions less than 1 mm. in diameter; moderately acid (pH 6.0); clear wavy boundary. (3 to 10 inches thick)
Bt1--9 to 16 inches; brown (10YR 4/3) (10YR 5/3 rubbed) silt loam, very dark brown (10YR 2/3) (dark brown, 10YR 3/3 rubbed) moist; weak coarse prismatic structure parting to weak medium subangular blocky; hard, friable, moderately sticky and moderately plastic; many very fine pores; one three-inch krotovina; very few faint clay films in channels and on peds; few uncoated silt grains on some vertical surfaces of prisms; few yellowish red and black soft concretions less than 1 mm. in diameter; moderately acid (pH 6.0); gradual wavy boundary. (0 to 8 inches thick)
Bt2--16 to 22 inches; brown (10YR 5/3) silt loam, dark brown (10YR 3/3) moist; weak coarse prismatic structure parting to weak medium and coarse subangular blocky; hard, firm, moderately sticky and moderately plastic; common fine and few medium roots; many very fine, few fine pores; one fine-inch krotovina; many faint clay films in channels and on peds; few uncoated silt grains on prism surfaces; soft concretions less than 1 mm. in diameter; moderately acid (pH 6.0); gradual wavy boundary. (0 to 7 inches thick)
E/B--22 to 27 inches; about 60 percent is light brownish gray (10YR 6/2), pale brown (10YR 6/3), and light gray (10YR 7/2) silt loam in pockets, streaks, specks, and many fine lenses, which are brown (10YR 4/3) and grayish brown (10YR 5/2) moist; about 40 percent is brown (10YR 5/3) silt loam that is brown (10YR 4/3) moist, and if rubbed is pale brown (10YR 6/3) dry and brown (10YR 4/3) moist; weak very coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine and medium roots; common very fine and few fine pores; very few faint clay films in channels and on peds; many soft reddish brown concretions less than 1 mm. in diameter; moderately acid (pH 6.0); gradual wavy boundary. (0 to 12 inches thick)
Eb--27 to 30 inches; light gray (10YR 7/2) silt loam, grayish brown (10YR 5/2) moist; weak coarse prismatic structure; hard, friable, slightly sticky and slightly plastic; few fine and medium roots; few very fine pores; many soft and many hard, black and reddish brown concretions up to 2 mm. in diameter; moderately acid (pH 5.7); abrupt irregular boundary. (1 to 11 inches thick)
B/Eb--30 to 34 inches; brown (10YR 5/3) silty clay loam, dark brown (10YR 3/3) moist; strong coarse prismatic structure; very hard, extremely firm, very sticky and very plastic; common fine roots in main vertical cracks; few very fine pores; a coating of light gray (10YR 7/2, 5/2 moist) silt loam, mantles the prisms 10 mm. thick at the top decreasing with depth to thin (fraction of a mm.) coating; continuous prominent brown (7.5YR 4/2) clay films on peds and in cracks; many soft reddish brown concretions less than 1 mm. in diameter and common hard black concretions 0.5 to 3 mm. in diameter; very strongly acid (pH 5.0); gradual wavy boundary. (0 to 4 inches thick)
Btb1--34 to 45 inches; brown (7.5YR 5/3) silt clay, dark brown (10YR 3/3) moist; weak very coarse prismatic structure parting to strong very coarse angular blocky and moderate medium subangular blocky; extremely hard, extremely firm, very sticky and very plastic; common fine roots in main vertical cracks; few very fine pores; continuous prominent clay films on peds and in pores; common black hard concretions 1 to 2 mm. in diameter; very strongly acid (pH 4.7); gradual wavy boundary. (7 to 12 inches thick)
Btb2--45 to 53 inches; brown (7.5YR 5/3) silty clay, brown (10YR 4/3) moist; weak medium prismatic structure parting to strong medium and fine angular and subangular blocky; extremely hard, very firm, very sticky and very plastic; few fine roots in vertical cracks; few very fine pores; continuous distinct clay films on blocky peds and in pores, and continuous prominent clay films on prism faces; many black stains on vertical surfaces of peds; common slightly hard black concretions; strongly acid (pH 5.4); gradual wavy boundary. (5 to 17 inches thick)
Btb3--53 to 65 inches; pale brown (10YR 6/3) silty clay brown (10YR 4/3) moist; weak medium prismatic structure parting to moderate fine angular blocky; very hard, firm, moderately sticky and moderately plastic; few fine roots; few very fine tubular pores; many distinct clay films on peds, and many prominent clay films in pores; few uncoated silt grains; common soft black concretions; slightly acid (pH 6.4); gradual wavy boundary. (2 to 15 inches thick)
Btssb--65 to 72 inches; brown (10YR 5/3) dark brown (10YR 3/3) silty clay loam, moist weak medium prismatic structure parting to strong medium and fine angular blocky; very hard, firm, very sticky and very plastic; few very fine and fine roots in main cracks few very fine pores; continuous distinct clay films on peds, in pores, and on coarse fragments; slickensides in places; many rounded and subangular, vesicular basalt fragments; common black coatings on peds; common black concretions; neutral (pH 6.7); irregular boundary. (1 to 11 inches thick)
2R--72 inches; basalt.
TYPE LOCATION: Idaho County, Idaho; about 6.7 miles northward on Kidder Ridge road from highway at Middle Fork Clearwater River bridge; 50 feet west of logging road and 440 feet north of gate along gravel road; in the SW1/4 NE1/4 section 22, T.33N., R.4E.
RANGE IN CHARACTERISTICS: Depth to bedrock is 40 to more than 60 inches. The soil is usually moist but is dry in all parts between depths of 4 and 12 inches for 45 to 60 days in most years in the late summer. The mean annual soil temperature ranges from 47 to 54 degrees F., and the mean summer soil temperature ranges from 59 to 65 degrees F.
The A horizon has hue of 10YR or 7.5YR, value of 3 to 5 dry, 1 to 3 moist and chroma of 1 to 3 dry or moist. It has 15 to 23 percent clay. Reaction is moderately acid to neutral.
The AB horizon, when present, has value of 3 to 5 dry and chroma of 2 to 4 dry and 2 to 3 moist. Texture is silt loam or silty clay loam. Clay content is 17 to 30 percent. Reaction is moderately acid to neutral.
The Bt horizon, when present, has hue of 10YR or 7.5YR, value of 4 to 6 dry, 2 to 4 moist and chroma of 2 to 4 dry or moist. It has less than 1.2 times more clay than the A horizon, and has none to many faint clay films on peds. Texture is silt loam or silty clay loam. Clay content is 23 to 30 percent. Reaction is slightly acid to neutral.
E/B or EB horizons, when present, have value of 3 to 6 dry, 3 to 5 moist and chroma of 2 to 4 dry, 2 or 3 moist. It is silt loam or silty clay loam with 17 to 28 percent clay. Reaction is moderately acid to neutral.
The E horizon has due of 10YR or 7.5YR, value 6 to 8 dry, 3 to 5 moist and chroma of 1 to 4 dry, 2 to 4 moist. It is silt loam or silty clay loam with 12 to 32 percent clay. Reaction is moderately acid to neutral. The lower part appears as capping over the B&A horizons.
The Btb horizon and BEb horizon, when present, has hue of 10YR or 7.5YR, value of 4 to 7 dry, 3 to 5 moist and chroma of 2 to 6 dry, 3 to 6 moist. It is silty clay loam or silty clay with 35 to 50 percent clay. It has 0 to 10 percent basalt gravel and 0 to 3 percent basalt cobbles in the lower part. Reaction is very strongly acid to neutral.
COMPETING SERIES: These are the Chicane, Nez Perce and Shebang series. Chicane soils are moderately alkaline in the lower Btb horizon and need further investigation to separate from Kooskia. Nez Perce and Shebang soils are calcareous at depths of less than 35 inches.
GEOGRAPHIC SETTING: Kooskia soils are on hills and drainageways on plateaus and benches in canyons. Slopes are 2 to 25 percent. The soils formed in loess over reworked loess and/or material from basalt. Elevation is 1,250 to 3,300 feet. The average annual precipitation is 22 to 33 inches. The average annual temperature is 45 to 52 degrees F. The frost-free period is 90 to 180 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Caribel, Gwin, and Klicker soils. Caribel soils lack E horizons. Gwin soils are shallow soils on south-facing slopes. Klicker soils are loamy-skeletal.
DRAINAGE AND PERMEABILITY: Moderately well drained with a perched water table during early spring; medium or rapid runoff; slow permeability.
USE AND VEGETATION: These soils are used for small grains, hay, pasture, and timber production. Native vegetation includes Douglas-fir, ponderosa pine, ninebark, wildrose, other shrubs, grasses, and forbs. In the drier end of the range of the series, Douglas-fir is lacking.
DISTRIBUTION AND EXTENT: Idaho County, Idaho. The soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Kooskia Area, Idaho, 1965.
REMARKS: Note: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - the zone from 0.3 to 4 inches (A horizon)
Argillic horizon - the zone from 30 to 72 inches (B/A and Btb horizons)
Particle-size control section - the zone from 30 to 50 inches (B/A, Btb1, and part of Btb2 horizon)
All depths to diagnostic horizons and features are measured from the top of the first mineral layer.
Note: The competing Chicane series is dry for 45 to 60 consecutive days, however, the Idaho fescue and bluebunch wheatgrass plant community appear more dry (i.e., more than 60 dry days).