LOCATION POTCHUB WAEstablished Series
TAXONOMIC CLASS: Medial, amorphic Aquandic Humicryods
TYPICAL PEDON: Potchub silt loam - forested. (Colors are for moist soil unless otherwise noted. All textures are apparent field textures.)
Oi--9 to 7 inches; leaves, needles and twigs.
Oa--7 inches to 0; decomposed organic litter.
A--0 to 7 inches; very dark brown (7.5YR 2/2) mucky silt loam, dark brown (7.5YR 3/2) dry; moderate coarse granular structure; slightly hard, friable, slightly sticky, slightly plastic and weakly smeary; many very fine, fine and medium roots, common coarse roots, many fine irregular pores; extremely acid (pH 4.4); abrupt wavy boundary. (5 to 8 inches thick)
E--7 to 10 inches; pinkish gray (7.5YR 7/2) silt loam, pinkish white (7.5YR 8/2) dry; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic and weakly smeary; many fine and medium and common coarse roots; few fine tubular pores; 5 percent pebbles; very strongly acid (pH 4.8); abrupt wavy boundary. (2 to 4 inches thick)
Bhs--10 to 13 inches; dark reddish brown (5YR 3/3) silt loam, reddish brown (5YR 4/3) dry; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic and weakly smeary; common fine, medium and coarse roots; few fine tubular pores; 5 percent pebbles; very strongly acid (pH 4.6); abrupt wavy boundary. (2 to 4 inches thick)
Bsl--13 to 17 inches; strong brown (7.5YR 5/6) silt loam, reddish yellow (7.5YR 7/6) dry; reddish brown (5YR 4/4) coatings on faces of peds; light reddish brown (5YR 6/4) dry; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic and weakly smeary; common fine, medium and coarse roots; few fine tubular pores; 5 percent pebbles; moderately acid (pH 5.8); abrupt wavy boundary. (3 to 10 inches thick)
Bs2--17 to 22 inches; strong brown (7.5YR 5/6) silt loam, light yellowish brown (10YR 6/4) dry, dark brown (7.5YR 4/4) coatings in cracks, dark yellowish brown (10YR 4/4) dry; slightly hard, friable, slightly sticky, slightly plastic and weakly smeary; few medium roots; few fine tubular pores; 5 percent pebbles; moderately acid (pH 5.8); clear wavy boundary. (0 to 12 inches thick)
Bs3--22 to 34 inches; dark brown (7.5YR 4/4) silt loam, light brown (7.5YR 6/4) dry; common fine faint strong brown (7.5YR 5/6) mottles, light brown (7.5YR 6/4) dry; massive; slightly hard, friable, slightly sticky, slightly plastic and weakly smeary; few fine tubular pores; 10 percent pebbles; moderately acid (pH 5.8); abrupt smooth boundary. (6 to 12 inches thick)
2Cd--34 to 60 inches; olive (5Y 5/3) dense glacial till that breaks to gravelly sandy loam, light olive gray (5Y 6/2) dry; extremely hard, very firm; few fine tubular pores; 20 percent pebbles; moderately acid (pH 5.8).
TYPE LOCATION: Snohomish County, Washington; 200 feet west and 600 feet north of SE corner of sec. 34, T. 32 N., R. 7 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature at a depth of 20 inches is 43 to 45 degrees F. Depth to the paralithic contact with dense glacial till and thickness of volcanic ash influence ranges from 20 to 40 inches. The particle-size control section averages 0 to 35 percent hard and 0 to 15 percent weathered rock fragments.
The A horizon has hue of 7.5YR or 10YR, value of 2 or 3 moist, 3 or 4 dry, and chroma of 1 or 2 moist and dry. It is extremely acid or very strongly acid. Some pedons lack an A horizon.
The E horizon has hue of 7.5YR or 10YR, value of 3 through 7 moist, 5 through 8 dry, and chroma of 1 through 4 moist and dry. Reaction is extremely acid or very strongly acid.
The Bhs and Bs horizons have hue of 5YR through 10YR, value of 3 through 5 moist, 4 through 7 dry, and chroma of 3 through 6 moist and dry. Texture is silt loam, loam, gravelly loam, or gravelly silt loam. Reaction is very strongly acid to moderately acid.
The 2Cd horizon has hue of 10YR through 5Y, value of 4 through 6 moist, 5 through 7 dry, and chroma of 2 through 4 moist and dry. It is dense glacial till that breaks to gravelly loam, gravelly sandy loam, very gravelly loam, or very gravelly sandy loam. It is very strongly acid to moderately acid.
COMPETING SERIES: These are the Diobsud, Gallup, Kulshan, and Vixen series. Diobsud soils are 20 to 35 percent phyllite fragments in the particle-size control section. Gallup and Vixen soils are more than 40 inches deep. Kulshan soils have a lithic contact at 20 to 40 inches.
GEOGRAPHIC SETTING: Potchub soils are on glacially modified mountain backslopes and plateaus at elevations of 2,600 to 3,600 feet. Slope is 3 to 90 percent. The soils formed in glacial till and volcanic ash. The till has mixed lithology. Potchub soils are in a cool marine climate with cool, dry summers, and cold, wet winters. The average annual precipitation ranges from 80 to 100 inches. The average annual temperature is about 42 degrees F. The frost-free season ranges from 90 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Hartnit soils and the Getchell, Oso, and Verlot soils. Getchell soils have less than 6 percent organic carbon in the upper 10 cm of the spodic horizon. Verlot soils have more than one half of spodic horizon of each pedon with a ratio of free iron to carbon of less than 0.2. Oso soils have a lithic contact at a depth of 20 to 40 inches.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to medium runoff; moderate permeability to the dense glacial till and very slow through it. A perched water table is as high as 1.5 to 3 feet at times from November through May.
USE AND VEGETATION: Used for woodland and wildlife habitat. Native vegetation is of western hemlock, Pacific silver fir, mountain hemlock and western redcedar, with an understory of western brackenfern, blue-leaved huckleberry, Oregon-grape, trailing blackberry, bunchberry, dogwood, deer fern, and longtube twinflower.
DISTRIBUTION AND EXTENT: West slopes of the Cascade Mountains in Snohomish and Whatcom Counties, Washington. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Snohomish County, Washington, 1979.
REMARKS: Except for the change from Cr to Cd, classification only updated 3/94 because of recent amendments to Soil Taxonomy. This pedon reflects a change in classification from coarse-loamy, mixed Humic Cryorthods to Medial Aquandic Humicryods. Diagnostic horizons and features recognized in this pedon are an albic horizon from 7 to 10 inches, a spodic horizon from 10 to 34 inches with more than 6 percent organic carbon in the upper 4 inches, and a paralithic contact at 34 inches with dense glacial till.