LOCATION BROMO WAEstablished Series
TAXONOMIC CLASS: Pumiceous or ashy-pumiceous over medial, glassy over amorphic, frigid Typic Udivitrands
TYPICAL PEDON: Bromo very cindery sandy loam - under a coniferous forest on a 27 percent west facing convex backslope at an elevation of 2,560 feet. (The soil was moist when described. Colors are for moist soil unless otherwise stated. All textures are apparent field textures.)
0--4 inches to 0; loose, partially decomposed organic litter, composed of needles, leaves, twigs, cones, wood and bark chips; abrupt wavy boundary. (l to 4 inches thick)
Al--0 to l inch; very dark gray (l0YR 3/l) very cindery sandy loam, gray (l0YR 6/l) dry; massive; soft, very friable, slightly sticky, nonplastic and weakly smeary; 40 percent rounded and subangular pebble-size pumice fragments (2-20 mm in diameter); strongly acid (pH 5.4); abrupt smooth boundary. (1/4 to 2 inches thick)
A2--l to 4 inches; dark brown (l0YR 3/3) very cindery sandy loam, brown (l0YR 5/3) dry; weak fine subangular blocky structure; soft, very friable, slightly sticky, nonplastic and weakly smeary; many very fine, fine, medium and coarse roots; common fine and medium pores; 40 percent rounded and subangular pumice fragments (2-20 mm in diameter); moderately acid (pH 5.6); abrupt smooth boundary. (3 to 6 inches thick)
AB--4 to l0 inches; very dark grayish brown (l0YR 3/2) very cindery sandy loam. light brownish gray (l0YR 5/2) dry; weak medium subangular blocky structure; soft, very friable, nonsticky, nonplastic and weakly smeary; common very fine and fine, few medium and coarse roots; 50 percent rounded and subangular pumice fragments (2-20 mm in diameter); moderately acid (pH 6.0); abrupt wavy boundary. (5 to l0 inches thick)
Bs--l0 to 23 inches; yellowish red (5YR 4/6) and strong brown (7.5YR 5/8) extremely cindery sand, reddish yellow (5YR 7/6 and 7.5YR 7/6) dry; single grained; loose; common very fine, fine and medium, few coarse roots; 75 percent rounded and subangular pumice fragments (2-20 mm in diameter); slightly acid (pH 6.2); abrupt wavy boundary. (l0 to l8 inches thick)
2Bsb1--23 to 35 inches; dark brown (l0YR 3/3) loam, light yellowish brown (l0YR 6/4) dry; moderate fine and very fine subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic and weakly smeary; few very fine, fine and coarse roots; common fine pores; l0 percent unweathered pebbles (2-l0 mm in diameter); moderately acid (pH 6.0); clear wavy boundary. (l0 to 20 inches thick)
2Bsb2--35 to 60 inches; dark yellowish brown (l0YR 4/4) loam, very pale brown (l0YR 7/4) dry; moderate medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic and weakly smeary; few very fine and fine roots; few fine pores; 5 percent unweathered pebbles; slightly acid (pH 6.4).
TYPE LOCATION: Lewis County, Washington; l,850 feet N. and l,000 feet W. of the southeast corner of sec. 3l, T. l4 N., R. 6 E., W.M.
RANGE IN CHARACTERISTICS: Mean annual soil temperature at a depth of 20 inches ranges from 42 to 44 degrees F. Depth to the buried profile is 20 to 35 inches. The umbric epipedon is l0 to l8 inches thick. Below the A horizon the soil is slightly acid or moderately acid.
The Al horizon has hue of l0YR or 2.5Y, value of 2 through 4 moist, 4 through 7 dry, and chroma of 0 through 2 moist and dry.
The A2 horizon has hue of l0YR or 7.5YR, value of 3 or 4 moist, 4 or 5 dry, and chroma of 2 or 3 moist and dry. It has 35 to 45 percent pebble-size pumice fragments.
The AB horizon has hue of l0YR or 7.5YR and chroma of 2 or 3 moist and dry. It has 45 to 55 percent multicolored pebble-size pumice fragments.
The Bs horizon has hue of 7.5YR, 5YR, or 10YR, value of 4 through 7 moist, 6 through 8 dry, and chroma of 2 through 8 moist and dry. It has 60 to 80 percent pebble- size pumice fragments.
The 2Bsb1 horizon has hue of l0YR or 7.5YR, value of 3 or 4 moist, 5 or 6 dry, and chroma of 3 or 4 moist and dry. It is loam or silt loam and has 5 to l0 percent unweathered pebbles.
The 2Bsb2 horizon has hue of l0YR or 7.5YR and value of 6 or 7 dry. It is loam, silt loam, sandy loam, gravelly loam or gravelly silt loam. Unweathered coarse fragments range from 5 to 25 percent and include both pebbles and cobbles.
COMPETING SERIES: These are the Bellicum, Benham, Cotteral and Skate series in other families. Bellicum soils are cindery over medial-skeletal. Benham soils lack a cambic horizon. Cotteral soils have a cryic temperature regime. Skate soils lack an umbric epipedon and have extremely gravelly loamy sand in the substratum.
GEOGRAPHIC SETTING: Bromo soils are on mountainslopes, benches and broad ridgetops at elevations of l,800 to 2,800 feet. Slopes are 0 to 65 percent. These soils formed in pumice and volcanic ash in the upper part and material weathered from andesite and volcanic ash in the lower part. The pumice layer is Mt. St. Helens "layer Y', deposited about 3,200 years ago. The climate is characterized by cool dry summers and cool wet winters. Mean annual precipitation is 70 to 90 inches including snowfall. Mean annual temperature is 42 to 44 degrees F. The growing season (28 degrees F.) is l50 to l80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Bellicum, Cotteral, and Skate soils and the Cispus, Nevat, Pheeney, and Cattcreek soils. Cispus and Nevat soils have a mesic temperature regime. Pheeney soils are medial-skeletal. Cattcreek soils have a spodic horizon and have a cryic temperature regime.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately rapid permeability in the surface soil and the upper part of the particle-size control section and moderate permeability below.
USE AND VEGETATION: Used for timber production, wildlife habitat and watershed. Overstory vegetation is western hemlock, Douglas-fir, western redcedar, red alder, bigleaf maple, and Pacific silver fir. Understory vegetation is Oregon-grape, western brackenfern, western swordfern, vine maple, salal, blue huckleberry, red huckleberry, trailing blackberry, oxalis, and redwood violet.
DISTRIBUTION AND EXTENT: West slopes of the Cascade Range in Lewis and Pierce Counties, Washington. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Lewis County, Washington, l976.
REMARKS: Classification only changed 4/94 because of recent amendments to Soil Taxonomy.
Laboratory data are available on these soils. Soil sample numbers are 78T7639 and 78T7640, Lewis County, Washington. Diagnostic horizons and features recognized in this pedon are: an umbric epipedon from the mineral surface to 10 inches, a spodic-like horizon from 10 to 35 inches, and a lithologic change from volcanic cindery to weathered volcanic ash at 23 inches. The spodic-like horizon does not meet chemical criteria for a spodic horizon but it is assumed to have silt-sized and larger pellets and cracked coatings.