LOCATION SVENSEN OR

Established Series
Rev. JAS/TDT/RWL
06/2011

SVENSEN SERIES

The Svensen series consists of deep and very deep, well drained soils formed in colluvium and residuum weathered from sandstone. Svensen soils are on mountains. Slopes are 0 to 90 percent. The mean annual precipitation is about 85 inches and the mean annual temperature is about 50 degrees F.

TAXONOMIC CLASS: Fine-loamy, isotic, isomesic Andic Humudepts

TYPICAL PEDON: Svensen medial loam, forested on a 31 percent slope and at an elevation of 210 feet. (Colors are for moist soil unless otherwise noted.)

Oi--0 to 3 inches; slightly decomposed litter of needles, twigs and leaves.

A1--3 to 11 inches; very dark brown (10YR 2/2) medial loam, grayish brown (10YR 5/2) dry; moderate fine and very fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; weakly smeary; many very fine roots; many very fine irregular pores; extremely acid (pH 4.0); clear wavy boundary.

A2--11 to 20 inches; dark brown (10YR 3/3) medial loam, brown (10YR 5/3) dry; moderate very fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; weakly smeary; common very fine roots; many very fine tubular pores; very strongly acid (pH 4.8); gradual wavy boundary. (Combined thickness of the A horizon is 10 to 21 inches)

Bw--20 to 41 inches; brown (10YR 4/3) loam, yellowish brown (10YR 5/4) dry; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; common very fine tubular pores; very strongly acid (pH 4.6); clear wavy boundary. (10 to 36 inches thick)

C--41 to 63 inches; variegated strong brown (7.5YR 4/6, 7.5YR 5/6) and light brownish gray (10YR 6/2) fine sandy loam, strong brown (7.5YR 5/6), reddish yellow (7.5YR 6/6), very pale brown (10YR 7/3) dry; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; common very fine tubular pores; extremely acid (pH 3.8).

TYPE LOCATION: Clatsop County, Oregon; about 6.2 miles southeast of Astoria, Oregon; south of spur road off Baseline Road, 1,900 feet north and 2,800 feet west of the southeast corner of section 25, T. 8 N., R. 9 W. Cathlamet Bay, Oregon USGS 7.5 minute topographic quadrangle. Latitude 46 degrees 08 minutes 46 seconds N. and Longitude 123 degrees 44 minutes 31 seconds W. NAD 27.

RANGE IN CHARACTERISTICS: The soil is usually moist and is dry for less than 45 consecutive days between the depths of 4 and 12 inches during the four month period following the summer solstice. The mean annual soil temperature is 47 to 54 degrees F. The difference between the mean winter and mean summer soil temperature is 5 to 9 degrees F. under canopy cover. The particle-size control section has greater than 15 percent particles 0.1 to 2.0 mm and less than 15 percent gravel. Rock fragments, when present, are angular and subangular in shape and are colluvial in origin. It is 40 to over 60 inches deep to a paralithic contact. The umbric epipedon is 10 to 21 inches thick. The upper 7 to 12 inches of the epipedon has an acid-oxalate aluminum plus one-half iron of 2.0 to 3.0 percent, a moist bulk density of 0.75 to 0.90 g/cc, phosphate retention of more than 85 percent, and 15-bar moisture of more than 15 percent. The lower part to a depth of 21 inches has an acid-oxalate aluminum plus one-half iron of 1.0 to 3.0 percent and a moist bulk density of 0.90 to 1.0 g/cc. Andic soil properties do not extend beyond 14 inches.

The A horizon has hue of 10YR or 7.5YR, value of 2 or 3 moist and 4 or 5 dry and chroma of 2 or 3 moist and dry. Texture is medial loam. It is 15 to 20 percent clay by field estimate and 0 to 10 percent gravel. It is extremely acid to strongly acid.

The Bw horizon has hue of 10YR or 7.5YR, value of 3 to 5 moist, 4 to 6 dry and chroma of 2 to 5 moist and dry. Texture is loam or clay loam with 20 to 30 percent clay and 0 to 10 percent gravel. It is extremely acid to very strongly acid.

The C horizon has variegated colors. Texture is loam, fine sandy loam or sandy loam and averages 15 to 25 percent clay with 0 to 35 percent sandstone paragravel. It is extremely acid to very strongly acid.

COMPETING SERIES: These are the Condorbridge, Grassyknob, Horseprairie, Reedsport and Skipanon series. Condorbridge soils are very deep, do not have an Oi horizon, and rock fragments, when present, are dominantly rounded and subrounded in shape derived from alluvial origin. Grassyknob and Reedsport soils are 20 to 40 inches deep to bedrock. Horseprairie soils have an umbric epipedon 20 to 40 inches thick. Skipanon soils have a particle-size control section with 15 to 30 percent gravel and 0 to 15 percent cobbles, with 5 to 20 percent paragravel in the lower part of the cambic horizon.

GEOGRAPHIC SETTING: Svensen soils are on ridgetops, side slopes, and foot slopes of mountains. Elevations are 20 to 1,300 feet. Slopes are 0 to 90 percent. The soils formed in colluvium and residuum weathered from dominantly from sandstone with some areas of metasedimentary or metavolcanic origin. The climate is characterized by cool wet winters and cool moist summers. Many summer days have fog or low cloud cover during the morning. The mean annual precipitation 60 to 100 inches. The mean annual temperature is 45 to 53 degrees F. The frost-free period is 145 to 270 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ecola, Knappa, Millicoma, Templeton and Walluski soils. Ecola and Templeton soils are on side slopes and ridgetops of mountains. Knappa and Walluski soils are on terraces. Ecola, Knappa, Templeton and Walluski soils are fine-silty. Millicoma soils are loamy-skeletal.

DRAINAGE AND PERMEABILITY: Well drained; moderately rapid permeability.

USE AND VEGETATION: These soils are used primarily for timber production. Other uses are homesites, hay and pasture, recreation and wildlife habitat. Native vegetation is Douglas-fir, western hemlock, red alder, Port-Orford cedar, sitka spruce, grand fir, thimbleberry, salal, salmonberry, vine maple and swordfern.

DISTRIBUTION AND EXTENT: Fog belt areas of the Coast Range Mountains, Oregon; MLRA 4A. The series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Clatsop County, Oregon 1984.

REMARKS: Diagnostic horizons and features recognized in this pedon:
Umbric epipedon - the zone from 3 to 20 inches (A1 and A2 horizons)
Cambic horizon - the zone from 20 to 41 inches (Bw horizon)
Andic subgroup feature - the zone from 3 to 20 inches (A1 and A2 horizons) with the zone from 3 to 11 inches having andic soil properties.
Particle-size control section - the zone from 13 to 43 inches (lower 7 inches of A2 horizon, the Bw horizon, and upper 2 inches of C horizon)

Depths to diagnostic horizons and features are measured from the top of the first mineral layer.

A proposal was submitted to NSSC (2000) to revise the definition of medial to also include those soil properties qualifying for the Andic subgroup under criteria #1 for andic soil properties. If accepted, medial modifiers would be used for those horizons meeting the andic subgroup criteria although not meeting andic soil properties.

National Cooperative Soil Survey
U.S.A.