LOCATION LAURELWOOD OREstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, mesic Ultic Haploxeralfs
TYPICAL PEDON: Laurelwood silt loam, cultivated. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 11 inches; dark brown (10YR 3/3) silt loam, brown (10YR 5/3) dry; moderate fine granular structure; slightly hard, very friable, nonsticky, slightly plastic; many fine roots; many fine irregular pores; common medium concretions; moderately acid (pH 5.8); abrupt smooth boundary. (10 to 12 inches thick)
BA--11 to 23 inches; dark brown (7.5YR 3/4) silt loam, brown (7.5YR 5/4) dry; weak coarse and medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic; many very fine roots; common very fine tubular pores; few fine concretions; moderately acid (pH 5.6); clear smooth boundary. (0 to 14 inches thick)
Bt1--23 to 32 inches; brown (7.5YR 4/4) silty clay loam, light brown (7.5YR 6/4) dry; strong medium subangular blocky structure; hard, firm, moderately sticky, moderately plastic; common very fine roots; common very fine tubular pores; many faint dark brown (10YR 3/3) clay films; few fine prominent black (10YR 2/1) manganese films; moderately acid (pH 5.6); clear smooth boundary. (9 to 13 inches thick)
Bt2--32 to 43 inches; yellowish brown (10YR 5/4) silty clay loam, light yellowish brown (10YR 6/4) dry; strong medium subangular blocky structure; hard, firm, moderately sticky, moderately plastic; few fine roots; common very fine tubular pores; many faint and distinct clay films; few fine prominent black (10YR 2/1) manganese films; moderately acid (pH 5.6); clear smooth boundary. (9 to 13 inches thick)
BCt--43 to 52 inches; yellowish brown (10YR 5/4) silty clay loam, light yellowish brown (10YR 6/4) dry; weak coarse and medium subangular blocky structure; hard, friable, moderately sticky, moderately plastic; common very fine tubular pores; common distinct clay films; common fine prominent black (10YR 2/1) manganese films; strongly acid (pH 5.4); clear smooth boundary. (0 to 24 inches thick)
2C1--52 to 62 inches; dark reddish brown (5YR 3/4) silty clay; massive; very hard, firm, moderately sticky and very plastic; few very fine tubular pores; few faint clay films in pores; many fine and medium prominent black (10YR 2/1) manganese films; strongly acid (pH 5.4); clear smooth boundary. (0 to 20 inches thick)
2C2--62 to 72 inches; yellowish red (5YR 4/6) silty clay; massive; very hard, firm, very sticky and very plastic; few faint clay films in pores; many fine and medium prominent black (10YR 2/1) manganese films; few fine igneous rock fragments; strongly acid (pH 5.4).
TYPE LOCATION: Washington County, Oregon; at the top of Iowa Hill in the extreme SW corner of the NW1/4 SW1/4 section 27, T.1S., R.3W. Willamette Meridian. (Latitude 45 degrees, 25 minutes, 46 seconds N; Longitude 123 degrees, 0 minutes, 57 seconds W. NAD 27) Laurelwood, Oregon USGS 7.5 minute topographic quadrangle.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 52 to 55 degrees F. The soils are usually moist but are dry for 45 to 60 consecutive days in all parts between depths of 4 and 12 inches following the summer solstice. The solum ranges from 4 to 10 feet or more thick over nonconforming horizons commonly weathered from members of the Columbia River Basalt Group (CRBG). Depth to bedrock commonly is more than 5 feet. The thinner sola are usually on ridgetops and steep canyon sides.
The A horizon has hue of 10YR or 7.5YR, value of 2 or 3 moist, 4 or 5 dry, and chroma of 2 or 3 moist and dry. It is a silt loam with 15 to 25 percent clay. It has 0 to 3 percent gravel. It has 1 to 15 percent Fe/Mn 1-10mm rounded to well rounded concretions. Reaction ranges from strongly acid to moderately acid.
The BA or AB horizons, when present, have hue of 10YR or 7.5YR, value of 3 or 4 moist, 4 or 5 dry, and chroma of 3 or 4 moist and dry. It is a silt loam or silty clay loam with 18 to 30 percent clay. It has 0 to 5 percent gravel. It has 1 to 10 percent Fe/Mn 1-10mm rounded to well rounded concretions. Reaction is moderately acid.
The Bt1 horizon has hue of 10YR or 7.5YR, value of 3 or 4 moist, 5 or 6 dry, and chroma of 4 to 6 moist and dry. It is a silty clay loam with 27 to 35 percent clay. It has 0 to 5 percent gravel. It has 1 to 5 percent Fe/Mn 1-10mm rounded to well rounded concretions. It has few to common prominent black (10YR 2/1) manganese films on faces of peds. Reaction is moderately acid.
The Bt2 horizon has hue of 10YR or 7.5YR, value of 3 to 5 moist, 5 or 6 dry, and chroma of 4 to 6 moist and dry. It is a silty clay loam with 27 to 40 percent clay. It has 0 to 5 percent gravel. It has 1 to 5 percent Fe/Mn 1-10mm rounded to well rounded concretions. It has few to common prominent black (10YR 2/1) manganese films on faces of peds. Reaction ranges from strongly acid to moderately acid.
The BCt horizon has hue of 10YR or 7.5YR, value of 4 to 5 moist, 5 or 6 dry, and chroma of 4 to 6 moist and dry. It is a silty clay loam or silty clay with 30 to 50 percent clay. It has 1 to 15 percent gravel, 0 to 15 percent cobbles, 0 to 50 percent paragravel, and 0 to 15 percent paracobbles. It has 1 to 5 percent Fe/Mn 1-10mm rounded to well rounded concretions. It has few to common prominent black (10YR 2/1) manganese films on faces of peds. Reaction ranges from strongly acid to moderately acid.
The 2C or 2Bt horizons have hue of 7.5YR, 5YR, or 2.5YR, value of 3 to 5 moist, 4 to 6 dry, chroma of 4 to 6 moist and dry. It is clay or silty clay with 40 to 55 percent clay. It has 0 to 30 percent gravel, 0 to 25 percent cobbles, 0 to 5 percent stones, 0 to 30 percent paragravel, and 0 to 25 percent paracobbles. It has 1 to 5 percent Fe/Mn 1-10mm rounded to well rounded concretions. It has few to many prominent black (10YR 2/1) manganese films on faces of peds. Reaction is strongly acid.
COMPETING SERIES: There are no competing series. A similar soil is Hillsboro. These soils are mollisols, have a superactive CEC class, and have stratified loamy and sandy material at depths of 40 inches or more.
GEOGRAPHIC SETTING: Laurelwood soils are on hills with long, convex, slopes that are gently sloping to very steep and have gradients of 3 to 60 percent and elevations of 200 to 1,600 feet. The soils formed in homogeneous, silty, loess-like material deposited probably in the middle Pleistocene overlying fine textured nonconforming materials commonly weathered from members of the Columbia River Basalt Group (CRBG). The climate is characterized by warm, wet winters and hot, dry summers. The mean annual rainfall is 45 to 60 inches. The average January temperature is 39 degrees F. and the average July temperature is 66 degrees F. The mean annual temperature is 51 to 53 degrees F. The frost-free period is 165 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cascade, Delena, Helvetia, Kinton, Kinton and Nekia soils. Cascade, Delena, and Kinton soils have fragipans, lack an argillic horizon and are on hills. In addition, Cascade soils are somewhat poorly drained, Delena soils are poorly drained and Kinton soils are moderately well drained. Helvetia soils are fine textured on lower footslopes. Nekia soils are fine textured and are 20 to 40 inches deep to basalt bedrock and are on foothills.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderate permeability.
USE AND VEGETATION: Most of these soils are cultivated. Orchards, berries, grain, hay and pasture are major crops. Native vegetation is mainly Douglas fir, bigleaf maple, Oregon grape, and hazelbrush.
DISTRIBUTION AND EXTENT: Northwestern Oregon. Laurelwood soils are on hills along the northwest margin of the Willamette Valley, Oregon. MLRA 2. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Washington County, Oregon, 1974.
REMARKS: Diagnostic horizons and features recognize in the pedon include:
Umbric epipedon from a depth of 0 to 11 inches (Ap horizon).
Argillic horizon from a depth of 23 to 52 inches Bt1, Bt2, and BCt horizons).
Nonconforming material from a depth of 52 to 72 inches (2C1 and 2C2 horizons).
Particle-size control section from a depth of 23 to 43 inches (Bt1 and Bt2 horizons)
Classification revised 3/2000 to reflect addition of superactive CEC class based on Keys to Soil Taxonomy.
Classification revised 1/2005 to active CEC class based on laboratory data.
Possibility exists that the Laurelwood concept is a Mollisol rather than Alfisol. Lab data collected to date (8 pedons) indicate 50% Alfisol and 50% Mollisol. Central concept of the series is located on a north slope and was likely forested in the past, which supports the Alfisol concept.
ADDITIONAL DATA: Characterization data from 8 representative pedons with User Pedon ID #s 59OR067005, 59OR067006, 02OR067002, 02OR067003, 03OR071006, 03OR071007, 03OR071008, and 03OR071009.