LOCATION BOISTFORT WAEstablished Series
TAXONOMIC CLASS: Medial over clayey, ferrihydritic over parasesquic, mesic Typic Fulvudands
TYPICAL PEDON: Boistfort silt loam - forested. (Colors are for moist soil unless otherwise stated. All textures are apparent field textures.)
Oi--0 to 2 inches; slightly decomposed twigs, needles, and some moss.
Al--2 to 11 inches; dark brown (7.5YR 3/2) medial silt loam, dark grayish brown (l0YR 4/2) dry; weak fine granular structure; soft, very friable, slightly sticky and slightly plastic, and weakly smeary; many coarse, medium and fine roots; many medium tubular pores; 25 percent firm shot-like concretions; very strongly acid; clear wavy boundary. (7 to 12 inches thick)
A2--11 to 21 inches; dark brown (7.5YR 3/2) medial silty clay loam, dark brown (l0YR 4/3) dry; moderate very fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic, and weakly smeary; many coarse, medium and fine roots; many medium tubular pores; few firm shot-like concretions; very strongly acid; clear wavy boundary. (0 to 10 inches thick)
2Bwl--21 to 39 inches; dark brown (7.5YR 4/4) silty clay, yellowish brown (l0YR 5/6) dry; weak fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic, and weakly smeary; few fine roots; common medium tubular and interstitial pores; extremely acid; gradual wavy boundary.
2Bw2--39 to 55 inches; strong brown (7.5YR 5/6) silty clay, strong brown (l0YR 5/8) dry; weak very fine subangular blocky structure; very hard, friable, moderately sticky and moderately plastic, and weakly smeary; few fine tubular and common medium interstitial pores; extremely acid; clear wavy boundary. (Combined thickness of the 2Bw horizon is 20 to 40 inches)
2BC--55 to 62 inches; strong brown (7.5YR 5/6) silty clay, yellowish brown (10YR 5/6) dry; weak very fine subangular blocky structure; very hard, friable, moderately sticky and moderately plastic, and weakly smeary; few fine tubular and common medium interstitial pores; extremely acid.
TYPE LOCATION: Thurston County, Washington; Capitol State Forest, about 5 miles northwest of Littlerock, 1,800 feet west and 600 feet north of the southeast corner of section 24, T. 17 N., R. 4 W.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 40 to more than 60 inches and depth to basalt is more than 60 inches. Rock fragments average less than 10 percent in the particle-size control section. The upper part of the 0 to 40 inch particle-size control section has an estimated moist bulk density of 0.75 to 0.90 g/cc, volcanic glass content of 5 to 20 percent, acid-oxalate extractable aluminum plus one-half iron of 1.0 to 2.0 percent, phosphate retention of 85 to 95 percent, and 15 bar water retention of 15 to 20 percent for air dried samples. Under forest cover, the mean annual soil temperature is about 50 degrees F. and ranges from 47 to 52 degrees F. The umbric epipedon is 14 to 20 inches thick.
The A horizon has value and chroma of 2 or 3 when rubbed and moist and and value and chroma are 2,3, or 4 when dry. This horizon is moderately acid to very strongly acid. It has 10 to 15 percent organic matter.
Some pedons have AB and BA horizons.
The 2Bw horizon has hue of 5YR or 7.5YR, value of 4 through 6 moist, 5 through 8 dry and chroma 3 through 6 moist, 5 through 8 dry. The apparent field texture averages clay loam, silty clay loam, or silty clay, but in some thin subhorizons it is gravelly or cobbly silty clay loam, gravelly or cobbly clay loam, or gravelly or cobbly silty clay. This horizon is moderately acid to extremely acid. It has 1 to 10 percent organic matter decreasing to less than 7 percent below 20 inches.
COMPETING SERIES: These are the Bunker and the similar Vesta soils. Bunker soils contain 15 to 35 percent rock fragments in the particle-size control section. Vesta soils are isomesic.
GEOGRAPHIC SETTING: Boistfort soils are on stable positions on foothills and mountains. Slopes range from 0 to 65 percent. The soils formed in material weathered from basalt. Elevations range from l00 to l,800 feet. These soils are in marine climate with cool wet winters and cool dry summers. Average annual precipitation ranges from 70 to 120 inches. The average January temperature is about 38 degrees F.; average July temperature is about 60 degrees F.; and the average annual temperature is about 50 degrees F. The growing season (28 degrees F.) is 200 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Bunker soils and the Astoria, Elochoman, Katula, Lates, Lytell, Murnen, and Zenker soils. Astoria soils have mixed mineralogy. Elochoman soils are medial over loamy. Lytell and Zenker soils are more than 35 percent weathered rock fragments in the particle-size control section. Katula soils have a lithic contact at 20 to 40 inches. Lates and Murnen soils are frigid.
DRAINAGE AND PERMEABILITY: Well drained; slow to moderate runoff; moderate permeability.
USE AND VEGETATION: Forested. Vegetation is mainly Douglas-fir, western redcedar, and red alder with an understory of western swordfern, Oregon-grape, red huckleberry, and vine maple.
DISTRIBUTION AND EXTENT: Southwestern Washington; series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Grays Harbor County (Grays Harbor County Area), Washington, 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are an umbric epipedon from 2 to 21 inches and a cambic horizon from 21 to 55 inches. The upper 19 inches of the particle-size control section has andic soil properties. The ratio of 15 bar water to clay is less than 1.0 and the CEC is less than 150 meq per 100g clay due to better than "normal" dispersion in one horizon. This description reflects a change in classification based on amendment 16. All depths to diagnostic horizons and features are measured from the top of the first mineral horizon.
ADDITIONAL DATA: Characterization data are available, pedon numbers 84P0906 and 40A3303.