LOCATION KAPOWSIN WAEstablished Series
TAXONOMIC CLASS: Coarse-loamy, isotic, mesic Andic Dystroxerepts
TYPICAL PEDON: Kapowsin gravelly ashy loam-pasture, at 794 foot elevation. (Colors are for moist soil unless otherwise stated)
Ap--0 to 7 inches; dark brown (10YR 3/3) gravelly ashy loam, brown (10YR 5/3) dry; weak very fine granular structure; slightly hard, very friable, slightly sticky, slightly plastic, weakly smeary; many roots; very few very fine pores; many black, 2 to 5mm, shot-like aggregates; 20 percent pebbles; few cobbles; NaF (pH 10.5); moderately acid (pH 5.6); clear smooth boundary. (2 to 9 inches thick)
Bhs--7 to 11 inches; dark brown (10YR 3/3) gravelly ashy loam, light brownish gray (10YR 6/2) dry; common fine faint, dark yellowish brown (10YR 4/4) mottles; weak fine subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic, and weakly smeary; common roots; few very fine pores; many black, 2 to 5mm, shot-like aggregates; 20 percent pebbles; NaF (pH 10.5) strongly acid (pH 5.5); clear wavy boundary (3 to 6 inches thick)
Bs1--11 to 16 inches; dark yellowish brown (10YR 4/4) gravelly ashy loam, pale brown (10YR 6/3) dry; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic, weakly smeary; common roots; few very fine pores; few black, 2 to 5mm, shot- like aggregates; 20 percent pebbles; NaF (pH 11.0); moderately acid (pH 5.8); clear wavy boundary. (5 to 15 inches thick)
Bs2--16 to 25 inches; brown (10YR 5/3) loam, very pale brown (10YR 7/3) dry; few fine faint redox concentrations; moderate medium subangular blocky structure; slightly hard, friable, moderately sticky, slightly plastic; common roots; few very fine pores; few black, 2 to 5mm, shot-like aggregates; 10 percent pebbles; moderately acid (pH 5.8); clear wavy boundary. (5 to 13 inches thick)
2Bstm--25 to 29 inches; olive brown (2.5Y 4/4, rubbed) loam, light brown (2.5Y 7/2) dry; many medium distinct dark yellowish brown (10YR 4/4) redox concentrations and light brownish gray (2.5Y 6/2) redox depletions along horizontal and vertical planes, weakly cemented; hard, firm, breaks into very rough plates; few very fine pores; distinct clay films in some pores and in places on plates; 10 percent pebbles; moderately acid (pH 5.8); abrupt irregular boundary. (4 to 20 inches thick).
2Cd1--29 to 59 inches; grayish brown (2.5Y 5/2) gravelly loam, light brownish gray (2.5Y 6/2) dry; massive; strongly compacted in places; hard, firm, moderately sticky, slightly plastic; few roots; few very fine pores; 20 percent pebbles; moderately acid (pH 5.8); gradual wavy boundary. (10 to 30 inches thick)
2Cd2--59 to 91 inches; grayish brown (2.5Y 5/2) gravelly loam, light gray (2.5Y 7/2) dry; massive; very compact in places; hard, friable, moderately sticky, slightly plastic; 20 percent pebbles; moderately acid (pH 5.8).
TYPE LOCATION: Pierce County, Washington; 2 miles south of Graham, on a 12 percent southeast-facing slope, along B.P.A. power line right-of-way, about 660 feet west and 1,603 feet south of the northeast corner of sec. 28, T. 18 N., R. 4 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature at a depth of 20 inches is about 50 degrees F. The lower part of the particle-size control section contains 15 to 30 percent coarse fragments, 45 to 60 percent sand and 5 to 15 percent clay. Few stones and cobbles occur throughout the solum. Depth to 2Bstm horizon ranges from 20 to 40 inches. The soil is strongly acid to slightly acid.
The A and Bhs horizons have hue of 10YR or 7.5YR, value of 3 or 4 moist, and chroma of 2 or 3 moist. It is gravelly loam or gravelly sandy loam.
The Bs horizon has hue of 7.5YR or 10YR, value of 3 through 6 moist, 6 or 7 dry, and chroma of 3 through 6 moist and dry. It is loam, silt loam, gravelly loam, or gravelly silt loam. Structure is weak or moderate. It commonly has redox concentrations but lacks redox features with chroma of 2 or less within 20 inches of the surface.
The 2Bstm horizon has value of 4 or 5 moist and chroma of 2 through 4 moist. It is loam and is gravelly in some pedons.
The 2Cd horizon has hue of 10YR or 2.5Y, value of 4 or 5 moist, and chroma of 3 or 4 moist and dry. It is sandy loam, or loam and is gravelly. This horizon has strata of clay, fine silt, sandy loam or sand, 3 to 10 inches in thickness.
COMPETING SERIES: These are the Alderwood, Bandon, Clipper, Harstine, Kickerville, Nati, Sehome, Squalicum, Tokul, and Yelm series in other families. Alderwood soils have more than 35 percent rock fragments in the control section. Bandon soils have less than 9 degrees F difference between mean sum er and mean winter temperature. Clipper and Yelm soils are deep and lack an ortstein layer. Harstine soils have 60 to 75 percent sand in the control section. Kickerville soils are sandy- skeletal in the lower part of the particle-size control section. Nati soils are underlain by shale or sandstone bedrock at a depth of 20 to 40 inches. Sehome soils lack the ortstein layer, Squalicum soils are deeper than 40 inches. Sehome and Tokul soils lack grayish mottles in the particle-size control section.
GEOGRAPHIC SETTING: Kapowsin soils are on convex or undulating glacial till plains and moraines at elevations from 50 to 900 feet. Slopes are 0 to 70 percent. These soils formed in compact glacial till. They occur in a mild marine climate having an average annual precipitation ranging from 30 to 50 inches. Mean January temperature is 40 degrees F; mean July temperature is 57 degrees F; and mean annual temperature is 50 degrees F. The summers are cool and dry. Winters are mild and wet with most of the annual precipitation occurring as rain from November through March. The frost-free season is about 150 to 200 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Alderwood soils and the Bellingham, Bow, Everett, Indianola, Kitsap, and Norma soils. Everett, Indianola, and Norma soils lack a pan. Bellingham and Bow soils lack a pan and are in a fine family. Kitsap soils lack a pan and are in a fine-silty family.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to medium runoff; moderate permeability to the pan, the pan is very slowly permeable. A perched water table is as high as 12 to 24 inches at times from December through June.
USE AND VEGETATION: Used for cropland, hay, pasture, urban development, woodland, and wildlife habitat. Native vegetation is Douglas-fir, western hemlock, western redcedar, red alder, and bigleaf maple, with an understory of trailing blackberry, salal, creambush oceanspray, western brackenfern, western swordfern, vine maple, Oregon-grape, red huckleberry, and evergreen blackberry.
DISTRIBUTION AND EXTENT: Puget lowlands in west central Washington. The series is of small extent.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Pierce County, Washington, 1940.
REMARKS: Classification only changed 4/94 because of recent amendments to Soil Taxonomy, except the Cr horizon was changed to Cd. Classification revised 1/200 from mixed, mesic Andic Durochrepts to isotic, mesic Andic Dystroxerepts based on revisions to Soil Taxonomy.
Diagnostic horizons and features include:
Ochric epipedon
Cambic horizon - from 7 to 25 inches
Cemented pan - from 25 to 29 inches and cemented with aluminum, iron, and organic matter
Densic materials - from 29 to 91 inches
Andic subgroup feature - from 0 to 25 inches with estimated properties of >5 percent volcanic glass, 1.0 to 2.0 percent and acid-oxalate Al + 1/2 Fe, and bulk density of 0.85 to 1.0 g/cc.
Oxyaquic feature - perched water table at 12 to 24 inches at times from December through June.
Particle-size control section - from 10 to 25 inches.
Depths to diagnostic horizons and features noted in the range of characteristics are measured from the top of the first mineral horizon.
This series needs further clarification as to the range in which redox depletions (chroma <2) can be found. As defined presently, if depletions occur between 20 and 30 inches aquic subgroup criteria would be met. This pedon does not meet Aquic subgroup criteria.