LOCATION BULL RUN OREstablished Series
TAXONOMIC CLASS: Medial, amorphic, mesic Eutric Fulvudands
TYPICAL PEDON: Bull Run silt loam, forested. (Colors are for moist soil unless otherwise noted.)
Oi--1 inch to 0; twigs, needles, leaves, cones, etc.
A--0 to 3 inches; very dark brown (10YR 2/2) silt loam, very dark grayish brown (10YR 3/2) dry; strong very fine and fine subangular blocky and fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and very fine irregular and tubular pores; many fine and medium roots; moderately acid (pH 5.6); clear wavy boundary. (2 to 12 inches thick)
AB--3 to 7 inches; very dark grayish brown (10YR 3/2) silt loam, brown (10YR 5/3) dry; strong very fine and fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and medium roots; many fine and very fine irregular and tubular pores; moderately acid (pH 5.7); clear wavy boundary. (0 to 7 inches thick)
BA--7 to 13 inches; dark yellowish brown (10YR 3/3) silt loam, yellowish brown (10YR 5/4) dry; moderate very fine, fine and medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; many fine, medium and coarse roots; many fine and very fine irregular and tubular pores; moderately acid (pH 5.7); gradual wavy boundary. (4 to 18 inches thick)
Bw--13 to 23 inches; dark yellowish brown (10YR 3/4) silt loam, yellowish brown (10YR 5/4) dry; weak very fine, fine and medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many fine, medium and coarse roots; many fine and very fine irregular and tubular pores; moderately acid (pH 5.8); clear wavy boundary. (6 to 18 inches thick)
BC--23 to 36 inches; dark yellowish brown (10YR 4/4) silt loam, light yellowish brown (10YR 6/4) dry; variegated with 30 percent dark yellowish brown (10YR 3/4) weak; very fine, fine and medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; common fine, medium and coarse roots; many fine and very fine tubular and irregular pores; moderately acid (pH 5.7); clear wavy boundary. (0 to 3 feet thick)
C1--36 to 54 inches; dark yellowish brown (10YR 4/4) silt loam, light yellowish brown (10YR 6/4) dry; massive; soft, friable, slightly sticky and slightly plastic; few fine, medium and coarse roots; many fine and very fine irregular pores; moderately acid (pH 5.8); gradual wavy boundary. (1 to many feet thick)
C2--54 to 73 inches; dark yellowish brown (10YR 4/4) silt loam, light yellowish brown (10YR 6/4) dry; massive; slightly hard, friable, slightly sticky and slightly plastic; trace of coarse fragments; few fine, medium and coarse roots; many very fine and irregular pores; moderately acid (pH 5.8).
TYPE LOCATION: Clackmas County, Oregon; along the south side Bull Run River Road, south of Bull Run Reservoir No. 2; NW1/4 NW1/4 section 36, T. 1 S., R. 5 E., W. M.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 47 to 54 degrees F. The soils have a udic moisture regime but have a short dry period of less than 45 consecutive days during the summer. Thickness of the solum ranges from 30 to over 60 inches. Depth to bedrock is 60 inches or more. The 60-inch profile is silt loam with measured clay of about 12 to 18 percent, a ratio of clay to 15-bar water of 1.0 or less, and a bulk density of about .70 to .85 gm/cc in the upper 2 feet of the profile. They have an average 15-bar water retention of about 15 to 20 percent in the particle-size control section. The phosphate retention is 90 to 100 percent, the acid oxalate extractable aluminum plus one-half iron is 2.0 to 4.0 percent. The soils are moderately to strongly acid. The umbric epipedon is 10 to 20 inches thick and has 8 to 13 percent organic matter.
The A horizon has value of 2 or 3 moist, 3 through 5 dry and chroma of 2 moist and dry. It has moderate or strong fine and very fine subangular blocky structure.
The B horizon has hue of 10YR or 7.5YR, value closest to 3 in upper part and 3 or 4 in the lower part when moist and 5 or 6 dry, and chroma of 3 in the upper part and 4 through 6 in the lower part moist and dry. It has weak or moderate very fine to medium subangular blocky structure.
The C horizon is mostly silt loam but gravelly glacial till is below depth of 40 inches in some pedons.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Bull Run soils are on hill slopes in lower valleys of mountainous areas at elevations of 100 to 2,500 feet. Slopes are 3 to 80 percent. The soils formed in loess with some admixture of ash. The climate is characterized by warm wet winters and hot moist summers. The mean annual precipitation is 60 to 105 inches. The mean annual temperature is 48 to 54 degrees F. The mean January temperature is 37 degrees F., and the mean July temperature is 65 degrees F. The frost-free period is 100 to 200 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ashcoff, Hoodview and the Wahkeena soils. These soils lack the dominance of pyroclastic materials and amorphous clays and have more than 35 percent rock fragments in the 10 to 40 inch control section.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: This soil is used mainly for timber production, watershed, recreation and wildlife habitat. Dominant overstory vegetation is Douglas fir, western hemlock, western redcedar, and red alder; dominant understory vegetation is western swordfern, Oregon oxalis, and vine maple.
DISTRIBUTION AND EXTENT: Lower valleys of the Cascade Mountains in northwest Oregon; MLRA 3.. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Clackamas County, Oregon, 1975.
REMARKS: This draft represents a change in classification from Medial, mesic Typic Hapludands to medial, amorphic, mesic Eutric Fulvudands.
Diagnostic horizons and features recognized in this pedon:
Umbric epipedon - from 0 to 13 inches (A, AB, and BA horizons)
Cambic horizon - from 13 to 36 inches (Bw and BC horizons)
Particle-size control section - from 0 to 40 inches (A, AB, BA, Bw, and BC horizons and upper 4 inches of C1 horizon)
Andic property ranges based on unpublished laboratory data from Oregon State University.
A1 (by 1n KCL) assumed to be less than 2.0 cmol/kg based on pH greater than 5.5 throughout the particle-size control section.
ADDITIONAL DATA: Characterization data on 3 profiles (FS61Oreg-045-4 (1-4), FS62Oreg-045-8(1-7), and FS64Oreg-045(43) by the Oregon State University. Unpublished.