LOCATION ROBER WAEstablished Series
TAXONOMIC CLASS: Medial over loamy, mixed over isotic, frigid Aquic Hapludands
TYPICAL PEDON: Rober silt loam, forested. (Colors are for moist soil unless otherwise noted. All textures are apparent field textures.)
0i--2 1/2 inches to 1 inch; leaves, needles and mosses.
0a--1 inch to 0; partially decomposed litter.
A--0 to 3 inches; very dark brown (10YR 2/2) silt loam, very dark grayish brown (10YR 3/2) dry; moderate fine granular structure; slightly hard, friable, slightly sticky, nonplastic, weakly smeary; common fine, medium and coarse roots; common fine tubular pores; strongly acid (pH 5.2); abrupt smooth boundary. (0 to 4 inches thick)
Bhs--3 to 7 inches; dark reddish brown (5YR 3/3 and 3/4) silt loam, brown (7.5YR 5/4) and dark brown (7.5YR 4/4) dry; moderate fine subangular blocky structure; slightly hard, very friable, slightly sticky, slightly plastic, weakly smeary; common fine, medium and coarse roots; common fine tubular pores; moderately acid (pH 6.0); abrupt smooth boundary. (3 to 9 inches thick)
Bs1--7 to 13 inches; reddish brown (5YR 4/4) and dark brown (7.5YR 4/4) silt loam, brown (7.5YR 5/4) and strong brown (7.5YR 5/6) dry; common medium dark reddish brown iron and organic stains on faces of peds; moderate medium subangular blocky structure; slightly hard, very friable, slightly sticky, slightly plastic, weakly smeary; few medium and fine roots; common fine tubular pores; moderately acid (pH 5.8); clear smooth boundary. (3 to 10 inches thick)
Bs2--13 to 22 inches; yellowish brown (10YR 5/4) silt loam, very pale brown and pale brown (10YR 7/3 and 6/3) dry; common fine brown iron and organic stains on faces of peds; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic, weakly smeary; few fine and medium roots; common fine tubular pores; slightly acid (pH 6.2); clear smooth boundary. (3 to 10 inches thick)
2C1--22 to 30 inches; grayish brown (10YR 5/2) and brown (10YR 5/3) silt loam, light gray (10YR 7/2) and very pale brown (10YR 7/3) dry; common medium faint dark yellowish brown (10YR 4/4) mottles; massive; finely stratified; hard, friable, slightly sticky, plastic, weakly smeary; very few fine roots; few fine tubular pores; moderately acid (pH 5.6); gradual smooth boundary. (4 to 15 inches thick)
2C2--30 to 60 inches; grayish brown (10YR 5/2) and brown (10YR 5/3) silty clay loam, light gray (10YR 7/2) and very pale brown (10YR 7/3) dry; common medium faint dark yellowish brown (10YR 4/4) mottles; massive; finely stratified; hard, friable, slightly sticky, plastic; few fine tubular pores; slightly acid (pH 6.2).
TYPE LOCATION: Snohomish County, Washington; 1,700 feet east and 20 feet north of the SW corner of section 12, T.30N., R.7E.
RANGE IN CHARACTERISTICS: The solum is 20 to 40 inches thick. These soils have a perched water table as high as 24 to 40 inches at times from December to May. Depth to mottles with chroma of 2 or less is more than 30 inches. The mean annual soil temperature at a depth of 20 inches ranges from 45 to 47 degrees F. The 10 to 40 inch control section has 0 to 5 percent rock fragments and 18 to 30 percent clay.
The A horizon has hue of 10YR or 7.5YR, value of 2 through 5 moist, 3 through 6 dry, and chroma of 2 or 3 moist or dry. It has moderate fine granular or moderate fine subangular blocky structure. This horizon is strongly acid or moderately acid. Some pedons have an E horizon up to 4 inches thick.
The Bs horizon has hue of 7.5YR or 5YR, value of 3 through 6 moist, 4 through 7 dry, and chroma of 3 through 6 moist or dry. It is silt loam or loam. This horizon has moderate fine or moderate medium subangular blocky structure. It is strongly acid to slightly acid.
The BC horizon has hue of 10YR or 7.5YR, value of 5 or 6 moist, 6 or 7 dry, and chroma of 3 through 5 moist or dry. It has moderate medium subangular blocky or prismatic structure. This horizon is strongly acid to slightly acid.
The C horizon has hue of 10YR, 5Y or 2.5Y, value of 4 through 6 moist, 5 through 7 dry, and chroma of 2 through 4 moist and dry. It is stratified silt loam and silty clay loam. This horizon is strongly acid to slightly acid.
COMPETING SERIES: These are the Saxon soils and the similar Tebo and Pastik series in other families. These soils are mesic. Saxon soils-- see remarks.
GEOGRAPHIC SETTING: Rober soils are on terraces, terrace escarpments, and mountain footslopes at elevations of 800 to 2,000 feet. Slopes are 0 to 65 percent. The soils formed in glacial lacustrine sediments containing volcanic ash. They have a cool marine climate with wet winters and dry summers. The average annual precipitation ranges from 60 to 100 inches. The mean annual temperature is 42 to 45 degrees F. and the frost-free season is 130 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Elwell, Olomount, Skykomish, and Tokul soils and the competing Pastik soils. Elwell soils have 5 to 30 percent percent rock fragments in the particle size control section and are underlain by dense glacial till at a depth of 20 to 40 inches. Olomount soils have a lithic contact at a depth of 20 to 40 inches. Skykomish soils are sandy-skeletal and have dense glacial till at a depth of 20 to 40 inches. Tokul soils are mesic.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to medium runoff; moderate permeability to the substra and slow through it. A perched water table is as high as 2 to 3.5 feet at times from December through May.
USE AND VEGETATION: Used for woodland and wildlife habitat. Native vegetation is western hemlock, Douglas-fir, western redcedar and red alder, with an understory of western swordfern, ladyfern, red huckleberry, western brackenfern, red elderberry, Oregongrape and vine maple.
DISTRIBUTION AND EXTENT: Valleys on the west slopes of the Cascade Mountains in northwest Washington. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Snohomish County, Washington, 1979.
REMARKS: Classification only updated 3/94 because of recent amendments to Soil Taxonomy. Diagnostic horizons and features recognized in this pedon are an ochric epipedon from the mineral surface to 3 inches and a cambic horizon from 3 to 13 inches.