LOCATION DIOBSUD WAEstablished Series
TAXONOMIC CLASS: Medial, mixed Andic Humicryods
TYPICAL PEDON: Diobsud gravelly silt loam - on a 31 percent southwest-facing slope under a coniferous forest canopy. (Colors are for moist soil unless otherwise stated. All textures are apparent field textures.)
0i--9 to 1 inch; forest litter. (2 to 9 inches thick)
0a--1 inch to 0; decomposed litter, common very fine and fine roots. (1 to 3 inches thick)
E--0 to 2 inches; grayish brown (10YR 5/2) gravelly silt loam, white (10YR 8/1) dry; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine roots; common very fine irregular pores; 15 percent rounded phyllite pebbles; NaF pH less than 9.2 very strongly acid (pH 5.0); abrupt smooth boundary. (1 to 5 inches thick)
Bhs--2 to 7 inches; dark reddish brown (5YR 3/4) gravelly silt loam, reddish yellow (7.5YR 6/6) dry; black (5YR 2/1) organic stains on faces of peds; weak medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic, weakly smeary; few fine roots; common very fine irregular pores; 20 percent rounded phyllite pebbles; NaF pH 12.0; very strongly acid (pH 5.0); abrupt wavy boundary. (4 to 7 inches thick)
Bs--7 to 13 inches; yellowish red (5YR 4/6) gravelly silt loam, reddish yellow (7.5YR 6/6) dry; weak medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic, weakly smeary; few very fine roots; common very fine irregular pores; 25 percent rounded phyllite pebbles; NaF pH 12.0; strongly acid (pH 5.4); abrupt smooth bounday. (2 to 6 inches thick)
BC--13 to 21 inches; olive (5Y 5/3) gravelly loam, pale yellow (5Y 8/3) dry; weak coarse subangular blocky structure; slightly hard, friable, slightly sticky; slightly plastic; few fine roots; common very fine irregular pores; 30 percent rounded phyllite pebbles; NaF pH 12.0; strongly acid (pH 5.2); clear wavy boundary. (6 to 12 inches thick)
C--21 to 28 inches; gray (5Y 5/1) gravelly loam, white (5Y 8/2) dry; weak coarse subangular blocky structure; slightly hard, friable, sticky, slightly plastic; very few very fine roots; few very fine irregular pores; 30 percent rounded phyllite pebbles; NaF pH 10.0; strongly acid (pH 5.4); abrupt smooth boundary. (5 to ll inches thick)
2Cd--28 to 60 inches; pale olive (5Y 6/3); dense glacial till breaking to a gravelly loam; white (5Y 8/2) dry; massive, very hard, very firm, sticky, slightly plastic; very few very fine irregular pores; 30 percent pebbles; strongly acid (pH 5/4).
TYPE LOCATION: Skagit County, Washington; approximately l,l60 feet south and l,200 feet east of the northwest corner, section 34, T. 36 N., R. 5 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 42 to 45 degrees F. Depth to dense glacial till which impedes roots and water movement is 20 to 40 inches. Soil reaction is very strongly acid or strongly acid throughout. The particle size control-section averages 20 to 35 percent unweathered phyllite fragments.
The E horizon has hue of 7.5YR or l0YR; value of 3 through 6 moist, 6 through 8 dry, and chroma of l or 2 moist and dry.
The Bhs and Bs horizon matrix have hue of 5YR or 7.5YR, value of 3 through 5 moist, 5 or 6 dry, and chroma of 4 through 6 moist and dry. The organic stains have hue of 2.5YR or 5YR, value of 2 or 3 moist and dry, and chroma of l or 2 moist and dry. It is gravelly silt loam or gravelly loam.
The BC horizon has hue of l0YR, 2.5Y or 5Y, value of 4 or 5 moist, 6 through 8 dry, and chroma of 2 or 3 moist and dry. It is gravelly loam or gravelly silt loam.
The C horizon has hue of 2.5Y or 5Y; value of 4 or 5 moist, 6 through 8 dry; and chroma of l through 3 moist and dry. It is gravelly loam or gravelly clay loam.
The 2Cd horizon is dense glacial till that breaks to gravelly loam, gravelly clay loam, or very gravelly loam.
COMPETING SERIES: These are the Gallup, Kulshan, Potchub, and Vixen soils. Gallup and Vixen soils are more than 40 inches deep. Kulshan soils have a lithic contact at 20 to 40 inches. Potchub soils have rock fragments of mixed lithology in the particle-size control section.
GEOGRAPHIC SETTING: Diobsud soils are on glacially modified mountain sides with slopes of 3 to 65 percent. The soils formed in glacial till high in phyllite with an admixture of volcanic ash. The range in elevation is 2,800 to 4,200 feet. The mean annual air temperature is 41 to 43 degrees F. The average annual precipitation is 85 to 95 inches. The average January temperature is 29 degrees F. and the average July temperature is 57 degrees F. The frost-free season is 90 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Crinker, Getchell, Springsteen and Wollard series. Getchell and Wollard soils have less than 6 percent organic carbon in the upper 10 cm of the spodic horizon. Crinker and Springsteen soils are 20 to 40 inches deep to a lithic contact.
DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is medium or rapid; permeability is moderate in the surface layer and subsoil to the dense glacial till and very slow through it. A perched water table is as high as 2 to 3 feet from December through April.
USE AND VEGETATION: Used for woodland and wildlife habitat. Native vegetation consists of Pacific silver fir, western hemlock, western redcedar, Alaska-cedar, and mountain hemlock with an undergrowth of tall blue huckleberry, bunchberry dogwood, queencup beadlily, red huckleberry, longtube twinflower, and deer fern.
DISTRIBUTION AND EXTENT: West slopes of the Cascade Mountains in northwestern Washington. This series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Skagit County area, Washington, 1982.
REMARKS: Classification and Cr changed to Cd 4/94. The previous draft reflected a change in classification from medial Humic Cryorthods to coarse-loamy, mixed Humic Cryorthods. Diagnostic horizons and features recognized in this pedon are an albic horizon from the mineral surface to 2 inches, a spodic horizon from 2 to 13 inches, andic soil materials from 0 to 28 inches, and a paralithic contact at 28 inches. The spodic horizon meets chemical criteria and averages more than 6 percent organic carbon in the upper 4 inches.