LOCATION TRASK OR
Established Series
Rev. GEO/AON
06/2011
TRASK SERIES
The Trask series consists of moderately deep, well drained soils that formed in colluvium and residuum weathered from siltstone. Trask soils are on mountainous uplands and have slopes of 3 to 90 percent. The mean annual precipitation is about 85 inches and the mean annual air temperature is about 48 degrees F.
TAXONOMIC CLASS: Loamy-skeletal, isotic, mesic Typic Humudepts
TYPICAL PEDON: Trask very shaly loam, burned over woodland. (Colors are for moist soil unless otherwise noted.)
Oi--0 to 3 inches; slightly decomposed litter of fir needles, leaves, twigs, and roots.
A1--3 to 8 inches; dark brown (7.5YR 3/2) very shaly loam, brown (7.5YR 5/2) dry; weak very fine granular structure; very friable, nonsticky and nonplastic; many fine roots; many very fine pores; about 40 percent fragments of shale and siltstone; many fine partially decomposed and charred roots fragments; very strongly acid (pH 4.8); clear wavy boundary. (3 to 7 inches thick)
A2--8 to 11 inches; dark brown (10YR 3/3) very shaly silt loam, brown (10YR 5/3) dry; shale and siltstone fragments are dark yellowish brown (10YR 3/4) moist; strong fine granular structure; friable, nonsticky and slightly plastic; many fine roots; many very fine pores; about 40 percent fragments of shale and siltstone; few fine partially decomposed and charred root fragments; very strongly acid (pH 4.8); clear wavy boundary. (2 to 5 inches thick)
Bw--11 to 17 inches; strong brown (7.5YR 5/6) and dark yellowish brown (10YR 3/3 and 3/4) extremely shaly silt loam, light yellowish brown (10YR 6/4) dry; weak fine subangular blocky structure; friable, slightly sticky and slightly plastic; common fine roots; common fine pores; about 70 percent rock fragments of shale and siltstone, mostly gravel size; very strongly acid (pH 4.6); gradual irregular boundary. (6 to 15 inches thick)
C--17 to 31 inches; variegated yellowish brown (10YR 5/4 and 5/6), brown (7.5YR 4/4), and strong brown (7.5YR 5/8) extremely shaly silt loam; massive; friable, moderately sticky and moderately plastic; few fine roots; few medium and large pores; 85 percent rock fragments of shale and siltstone, mostly gravel size; soil material primarily in small pockets and along root channels; many rock fragments have black stains on their surfaces; very strongly acid (pH 4.6); clear wavy boundary. (9 to 16 inches thick)
Cr--31 to 51 inches; partially consolidated fractured siltstone with few roots extending to 51 inches.
TYPE LOCATION: Tillamook County, Oregon; 0.8 mile up old landing road from Cedar Butte Lookout Road which leaves Tillamook-Portland highway 18 miles east of Tillamook; extreme NE1/4 NE1/4 NW1/4 section 36, T.1N., R.8W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 47 degrees to 54 degrees F. The soil is usually moist and is dry for less than 45 consecutive days between depths of 4 and 12 inches. The solum ranges from 12 to 25 inches in thickness but most areas range from 12 to 20 inches. Depth to the paralithic contact is 20 to 40 inches with most pedons ranging from 20 to 30 inches. The umbric epipedon is 7 to 10 inches thick.
The A horizon has hue of 10YR or 7.5YR, value of 2 or 3 moist and chroma of 2 or 3 moist and dry. It is commonly very shaly or shaly loam with 18 to 27 percent clay. Rock fragments of shale range from 35 to 75 percent. These are mostly gravel size. This horizon has moderate or strong granular or subangular blocky structure.
The Bw horizon has hue of 7.5YR or 10YR, value of 3 through 5 moist, 5 through 7 dry, and chroma of 3 through 6. It is silt loam or silty clay loam and has 20 to 30 percent clay and 50 to 75 percent rock fragments.
The C horizon has 65 to 85 percent rock fragments of shale and siltstone intermingled with soil material similar to the Bw horizon.
The Cr horizon is partially consolidated and fractured to depths of 40 inches or more, but it is consolidated below 40 inches in some pedons.
COMPETING SERIES: These are the Crescent,
Itswoot,
Klone and
Watt series. All of these soils except Watt have ochric epipedons and are deeper than 40 inches to bedrock. Watt soils have hue of 2.5Y or 5Y throughout.
GEOGRAPHIC SETTING: The Trask soils are on steep and mountainous uplands at elevations of 500 to 2,500 feet. They formed in residuum and colluvium weathered from shales and siltstones. They have a humid climate with cool dry summers and cool moist winters. Many summer days have fog or low cloud cover during the mornings. The annual precipitation is 70 to 100 inches and more. The mean July temperature is about 59 degrees F., mean January temperature is about 38 degrees F., and mean annual temperature is 45 to 52 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Astoria,
Ecola,
Melby and
Winema soils. Astoria, Melby and Winema soils are clayey and have less than 35 percent rock fragments in their profiles. Ecola soils have less than 35 percent rock fragments in their profiles.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Timber production. Native vegetation is Douglas-fir, western hemlock, alder, vine maple, red huckleberry, thimbleberry, sword and brackenfern and salal.
DISTRIBUTION AND EXTENT: Coast Range is western Oregon; MLRA 1. The soil is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Tillamook County, Oregon, 1963.
REMARKS: Diagnostic horizons and other features;
Umbric epipedon - from 3 to 11 inches
Cambic horizon - from 11 to 17 inches
Humudept- the soil has an umbric epipedon that is 8 inches thick as the base of the cambic horizon is 14 inches below the top of the mineral soil surface; thus the umbric epipedon is greater than one-third the thickness of the solum.
National Cooperative Soil Survey
U.S.A.