LOCATION WILLAPA WAEstablished Series
TAXONOMIC CLASS: Medial, ferrihydritic, isomesic Aquic Fulvudands
TYPICAL PEDON: Willapa medial silt loam, on a west facing 3 percent slope, planted to fir. (Colors are for moist soil unless otherwise stated. All textures are apparent field textures.)
Oi--0 to 1 inch; slightly decomposed accumulation of leaves and twigs.
A1--1 to 11 inches; dark brown (7.5YR 3/2) medial silt loam, grayish brown (10YR 5/2) dry; strong fine and medium subangular blocky structure; hard, friable, slightly sticky, slightly plastic and weakly smeary; common medium, many fine and very fine roots; many very fine interstitial pores; strongly acid (pH 5.2); gradual smooth boundary. (7 to 11 inches thick)
A2--11 to 19 inches; dark brown (10YR 3/3) medial silt loam, brown (10YR 5/3) dry; moderate fine and medium subangular blocky structure; hard, friable, slightly sticky, plastic and weakly smeary; common very fine and fine roots; common very fine and fine tubular pores; strongly acid (pH 5.4); clear smooth boundary. (7 to 10 inches thick)
Bw--19 to 44 inches; dark yellowish brown (10YR 4/4) medial silty clay loam, light yellowish brown (10YR 6/4) dry; common fine and medium prominent strong brown (7.5YR 5/8) redox concentrations, reddish yellow (7.5YR 6/8) dry; weak fine subangular blocky structure; hard, firm, moderately sticky, moderately plastic and weakly smeary; few very fine roots; common very fine and fine tubular pores; strongly acid (pH 5.4); clear smooth boundary. (20 to 30 inches thick)
C--44 to 61 inches; pale brown (10YR 6/3) silty clay loam, very pale brown (10YR 7/3) dry; many fine and medium prominent strong brown (7.5YR 5/8) redox concentrations and common fine and medium distinct grayish brown (2.5Y 5/2) redox depletions, reddish yellow (7.5YR 6/8) and light gray (2.5Y 7/2) dry; massive; hard, firm, moderately sticky, moderately plastic and weakly smeary; few very fine roots; few very fine tubular pores; strongly acid (pH 5.4).
TYPE LOCATION: Pacific County, Washington; 8 miles southwest of South Bend along U. S. Highway 101, intersection of the Bone River C-line and C-100 spur; 500 feet east, 200 feet north of SW corner of section 3, T.13N., R.10W.
RANGE IN CHARACTERISTICS: The solum is 35 to 50 inches thick. The mean annual soil temperature is 47 to 51 degrees F. The difference between the mean summer and mean winter soil temperature is 5 to 9 degrees F. These soils range from moderately acid to very strongly acid. Depth to redox features (depletions) with a chroma of 2 or less is 35 to 45 inches.
The A horizon has hue of 7.5YR or 10YR, value of 3 moist, 4 or 5 dry, and chroma of 2 or 3 moist and 2 through 4 dry. It has moderate or strong fine or medium granular or subangular blocky structure.
The B horizon has hue of 5YR or 10YR, value of 3 through 5 moist, 5 through 7 dry, and chroma of 4 through 6 moist or dry. It is medial silt loam or medial silty clay loam with less than 35 percent clay. It has weak to strong medium subangular blocky structure. The lower part of the B horizon has redox depletions with a chroma of 2 or less in some pedons.
The C horizon has hue of 5Y through 10YR, value of 4 through 6 moist, 6 or 7 dry, and chroma of 3 through 6 moist or dry. It is stratified silt loam or silty clay loam. It is stratified in some pedons.
COMPETING SERIES: These are the Astoria, Boistfort, Bunker, Elochman, Ilwaco, Kinney, Knappton, Lebam, Le Bar, Lytell, Narel, Palix, Silcox, Swem, Sylvia, Vesta, Wahkiakum, Wellman and Zenker series. All of the competing soils except Swem and Sylvia lack mottles with chroma of 2 or less and are well drained. Also, Kinney soils have 25 to 35 percent hard rock fragments in the control section. Knappton soils have 15 to 35 percent hard rock fragments in the control section. Palix and Lytell soils have 20 to 80 percent and 45 to 85 percent soft siltstone rock fragments respectively in the control section. Narel and Zenker soils have 30 to 70 percent and 60 to 75 percent soft sandstone rock fragments respectively in the control section. Silcox, Wahkiakum, and Wellman soils have 10 to 35 percent hard rock fragments in the control section. Swem soils have 15 to 35 percent hard basalt fragments in the upper part of the control section and 10 to 15 percent soft siltstone rock fragments in the lower part of the control section. Sylvia soils have mottles with chroma of 2 or less at a depth of less than 20 inches.
GEOGRAPHIC SETTING: Willapa soils are on broad marine terraces along the periphery of Willapa Bay, at elevations from sea level to about 400 feet. Slopes are 1 to 65 percent slopes. The slope shapes are characterized by a steep linear shoulder, concave foot and gentle, linear toe slope. Willapa soils formed in thinly bedded, highly stratified marine sand, silt and clay. They occur in a coastal fog belt are and the mean annual precipitation ranges from 80 to 120 inches. The average January temperature is 39 degrees F.; the average July temperature is 62 degrees F.; and the mean annual temperature is 48 degrees F. The growing season (28 degrees F.) is 180 to 220 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Newskah soils and the competing Ilwaco, Knappton, Lebam, Narel, Palix and Vesta soils. Newskah soils have similar landforms and may occupy the same geomorphic surface but are distinguished by their textured control section and are well drained.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow runoff; moderately slow permeability.
USE AND VEGETATION: Timber production, wildlife habitat, and recreation are the principal uses. Western hemlock and Douglas fir are the major species, with widely spaced Sitka spruce and western red cedar. Understory species are salal, vine maple, huckleberry, Oregon grape, salmonberry, brachenfern and swordfern.
DISTRIBUTION AND EXTENT: Willapa Harbor area of western Washington; MLRA 4A. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Pacific County (Pacific County Area), Washington, 1978.
REMARKS: Classification only changed 4/94 because of recent amendments to Soil Taxonomy. The cool phase map units characterized with Pacific Silver Fir should be re-correlated to an isofrigid soil series.