LOCATION HOKO WAEstablished Series
TAXONOMIC CLASS: Medial-skeletal, ferrihydritic, isomesic Aquic Durudands
TYPICAL PEDON: Hoko gravelly medial silt loam, forest. (Colors are for moist soil unless otherwise stated.)
Oi--0 to 3 inches; slightly decomposed needles, leaves, twigs, bark, and moss.
Oe--3 to 5 inches; moderately decomposed organic matter. (Combined thickness of the O horizon is 1 to 6 inches.)
A--5 to 9 inches; dark reddish brown (5YR 3/2) gravelly medial silt loam, reddish gray (5YR 5/2) dry; moderate medium and coarse granular structure; slightly hard, friable, slightly sticky and slightly plastic; weakly smeary; many fine, medium, and coarse roots; common medium interstitial and few fine and medium tubular pores; 30 percent rounded gravel including some cobbles; strongly acid (pH 5.2); clear wavy boundary. (3 to 5 inches thick)
BA--9 to 13 inches; dark reddish gray (5YR 4/2) very gravelly medial silt loam, light reddish brown (5YR 6/3) dry; moderate fine and medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; many fine, medium, and coarse roots; common fine and medium interstitial and common fine and medium tubular pores; 35 percent rounded gravel including some cobbles; strongly acid (pH 5.4); clear wavy boundary. (0 to 5 inches thick)
Bw1--13 to 17 inches; brown (7.5YR 4/4) very gravelly medial silt loam, pink (7.5YR 7/4) dry; common fine and medium distinct yellowish red (5YR 5/6) redox concentrations; moderate medium and coarse subangular blocky structure; hard, friable, moderately sticky and moderately plastic; weakly smeary; many fine and medium coarse roots; common fine and medium interstitial and tubular pores; 35 percent rounded gravel including some cobbles; strongly acid (pH 5.5); gradual wavy boundary. (3 to 6 inches thick)
Bw2--17 to 21 inches; strong brown (7.5YR 5/6) very gravelly medial silt loam, reddish yellow (7.5YR 7/6) dry; many medium and coarse faint brown (7.5YR 4/4) redox concentrations; weak medium and coarse subangular blocky structure; hard, friable, moderately sticky and moderately plastic; weakly smeary; common fine and medium roots; common fine and medium interstitial and tubular pores; 35 percent rounded gravel including some cobbles; moderately acid (pH 5.6); gradual wavy boundary. (3 to 12 inches thick)
Bw3--21 to 27 inches; strong brown (7.5YR 5/8) very gravelly medial silty clay loam, reddish yellow (7.5YR 8/6) dry; few fine faint brown (7.5YR 4/4) redox concentrations; weak medium and coarse prismatic, and weak very fine and fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; weakly smeary; common fine and medium roots; common fine and medium interstitial and tubular pores; 30 percent rounded gravel, about 10 percent small and medium cobbles; moderately acid (pH 5.6); clear smooth boundary. (5 to 10 inches thick)
2Bsm--27 to 34 inches; pale brown (10YR 6/3) moderately cemented glacial till that crushes to gravelly silty clay loam, very pale brown (10YR 8/2) dry; massive; very hard, firm, moderately sticky and moderately plastic; few fine interstitial pores; 30 percent rounded gravel; dark reddish brown (2.5YR 2/4) and black (10YR 2/1) iron and manganese stains along fractures or plates; moderately acid (pH 5.7); gradual wavy boundary. (5 to 17 inches thick)
2Cd--34 to 60 inches; pale brown (10YR 6/3) dense till that slakes to gravelly silty clay loam, very pale brown (10YR 8/2) dry; massive; very hard, very firm, moderately sticky and moderately plastic; few fine interstitial pores; 30 percent rounded gravel; moderately acid (pH 5.7).
TYPE LOCATION: Jefferson County, Washington; SE1/4 NE1/4 NW1/4 sec. 29, T.24N., R.12W. 1/2 mile east of the Clearwater River Road along the Boulder Creek logging road, 15 feet north of the road.
RANGE IN CHARACTERISTICS: 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. The soils are usually moist and have a udic soil moisture regime. The solum and depth to cemented till is 20 to 40 inches. The solum has andic soil properties throughout with moist bulk density of 0.50 to 0.90 g/cc, acid oxalate extractable aluminum plus one-half of the acid oxalate extractable iron is 2 to 4 percent, phosphate retention is 85 to 100 percent, and 15-bar water retention is 25 to 35 percent on air dried samples. The particle-size control section has 35 to 70 percent rounded rock fragments. Acid oxalate iron is 1.5 to 3.0 percent. The solum has 2 to 3 cmol/kg of aluminum. Depth to redox concentrations is 8 to 20 inches.
The A and BA horizons has hue of 5YR or 7.5YR, have value of 2 to 4 moist, 5 or 6 dry and chroma 2 to 4 moist and dry. It has 10 to 20 percent organic matter. It is very strongly or strongly acid.
The Bw horizon has hue of 5YR or 7.5YR, value of 4 or 5, and chroma of 4 to 6. It is very gravelly medial silt loam, very gravelly and extremely gravelly medial loam, very gravelly medial silty clay loam or very gravelly medial clay loam. It has 2 to 10 percent organic matter with less than 7 percent below 10 inches. It is very strongly or moderately acid.
The 2Bsm horizon has hue of 10YR or 5Y, value of 4 to 6, and chroma of 2 or 3. It is weakly to moderately cemented by iron, aluminum and manganese. It is loamy sand, sandy loam, loam or silty clay loam with 30 to 65 percent rounded rock fragments.
The 2Cd horizon is silty clay loam or silt loam with 15 to 20 percent rounded gravel.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Hoko soils occur on ground moraines on till plains and mountains. Elevations of 50 to 1,500 feet. The soils formed in alpine glacial till over cemented basal till derived from sandstone, shale, metamorphosed slate, phyllites, and graywacke. These soils occur in a wet cool marine climate having an annual precipitation of 90 to 170 inches; average summer temperature is 59 degrees F.; average winter temperature is 40 degrees F.; and mean annual temperature is 49 degrees F. The frost-free period is 140 to 220 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Copalis, Kalaloch, Mopang and Southshore soils. Copalis and Mopang soils are medial. Kalaloch soils are medial over sandy or sandy- skeletal. Southshore soils are deep to cemented till.
DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is slow to rapid depending on slope and rainfall intensity. Permeability of the solum is moderate and of the 2Bsm horizon very slow.
USE AND VEGETATION: Forestland. Native vegetation is western hemlock, grand fir, bigleaf maple, red alder, western redcedar, and Sitka spruce with an understory of vine maple, western swordfern, deer fern, red huckleberry, blueleaved huckleberry, red elderberry, cascara buckthorn, salal, and salmonberry.
DISTRIBUTION AND EXTENT: Northwest Washington; MLRA 4A. Series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Clallam County, Washington, 1937.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
- ochric epipedon
- cambic horizon from 13 to 27 inches, and cemented till at 27 inches
- This series meets Fulv great group criteria and does not meet Eutric subgroup criteria as given for Fulvudands.
- All depths to diagnostic horizons and features are measured from the top of the first mineral horizon.
Preliminary data on this series (pedon number 83P-169-174) shows the till to be cemented by iron, aluminum and organic matter.