LOCATION DEMENT OR
Established Series
Rev. JTH-GLG
06/2011
DEMENT SERIES
The Dement series consists of deep, well drained soils that formed in residuum and colluvium weathered from sedimentary rocks. Dement soils are on mountains and have slopes of 2 to 70 percent. The mean annual temperature is about 53 degrees F, and the mean annual precipitation is about 65 inches.
TAXONOMIC CLASS: Fine, isotic, mesic Humic Dystrudepts
TYPICAL PEDON: Dement silt loam - on a 5 percent convex southeast- facing slope in forested area. (Colors are for moist soil unless otherwise noted.)
A--0 to 7 inches; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; moderate fine and medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine to medium roots; many very fine pores; slightly acid (pH 6.2); abrupt smooth boundary. (7 to 9 inches thick)
Bw1--7 to 23 inches; reddish brown (5YR 4/3) silty clay loam, brown (7.5YR 5/4) dry; moderate fine and medium subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; common very fine to medium roots; many very fine to medium pores; common thin reddish brown (5YR 4/4) coatings on peds; very strongly acid (pH 5.0); clear smooth boundary. (14 to 20 inches thick)
Bw2--23 to 36 inches; reddish brown (5YR 4/4) silty clay loam, brown (7.5YR 5/4) dry; weak medium subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; common fine to medium roots; common very fine and fine pores; few thin reddish brown (5YR 4/4) coatings on peds; strongly acid (pH 5.4); clear smooth boundary. (10 to 19 inches thick)
Bw3--36 to 45 inches; reddish brown (5YR 4/4) silty clay loam, brown (7.5YR 5/4) dry; weak coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common fine and medium roots; few very fine pores; very few thin reddish brown coatings on peds; strongly acid (pH 5.4); clear smooth boundary. (8 to 12 inches thick)
2Cr--45 to 72 inches; variegated partially weathered sedimentary bedrock with common fine and medium red (2.5YR 5/6) iron stains along fracture planes of upper part.
TYPE LOCATION: Coos County, Oregon; 2 miles northeast of Coquille on the north side of the Coquille-Fairview road; 2,000 feet east and 200 feet north of the southwest corner, sec. 30, T. 27 S., R. 12 W.
RANGE IN CHARACTERISTICS: The soils are usually moist, but have a short dry period of less than 45 consecutive days during the summer. Up to 15 percent gravel are in the lower part of the solum. The solum thickness and depth to soft bedrock is 40 to 60 inches.
The A horizon has hue of 5YR to 10YR, and chroma of 2 to 4 moist and dry. It has moderate or strong granular, or very fine or fine subangular blocky structure. Forested areas commonly have a 1- to 4-inch thick O horizon. It is very strongly acid to slightly acid.
The Bw horizon has hue of 5YR moist and 5YR or 7.5YR dry, value of 4 or 5 moist, 5 or 6 dry, and chroma of 3 or 4 moist and dry. It is silty clay loam or silty clay and is 35 to 45 percent clay. It is very strongly acid or strongly acid.
The 2Cr horizon is siltstone or sandstone in various stages of weathering. Fragments are often separated and mixed with silty clay material. Red iron stains coat vertical and horizontal fracture planes.
COMPETING SERIES: These are the
Blachly,
Desolation,
Kilowan,
Melby, and
Willaby series. Blachly soils are deeper than 80 inches to bedrock and have more than 45 percent clay in the Bt horizon. Desolation soils have formed in colluvium from basalt. The particle-size control section has 5 to 35 percent rock fragments. The lower part of the subsoil (below 40 inches) has 35 to 75 percent rock fragments. Kilowan soils are 20 to 40 inches deep to a paralithic contact. Melby soils have hue of 7.5YR moist in the Bw horizon. Willaby soils have 15 to 60 percent rounded gravel and cobbles in the lower 2B horizon.
GEOGRAPHIC SETTING: Dement soils are on uneven dissected complex slopes on mountains. Elevation is 20 to 900 feet. Slopes range from 2 to 70 percent. The marine climate is characterized by cool moist winters and mild dry summers. The mean annual temperature is 50 to 53 degrees F, mean January temperature is about 44 degrees F, and mean July temperature is about 60 degrees F. The mean annual precipitation is 55 to 80 inches. The frost-free period is 180 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Honeygrove,
Millicoma,
Salander,
Templeton, and
Winchuck soils. Honeygrove soils have an argillic horizon with more than 50 percent clay. Millicoma, Salander and Templeton soils have an umbric epipedon. Templeton soils are in the fine-silty family. Millicoma soils are in the loamy-skeletal family and Salander soils are in the medial family. Winchuck soils have an umbric epipedon and an argillic horizon above a stratified medium to fine textured C horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderately slow permeability.
USE AND VEGETATION: Used for timber, pasture, urban development, wildlife, and recreation. The natural vegetation is dominantly Douglas-fir, western hemlock, evergreen huckleberry, poison-oak, western redcedar, shrubs and grass.
DISTRIBUTION AND EXTENT: Southwestern Oregon; MLRA 1. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Coos County, Oregon, 1983.
REMARKS: Diagnostic horizons and other features;
Ochric epipedon
Humic subgroup - color requirement is met from 0 to 7 inches
Cambic horizon - from 7 to 45 inches
ADDITIONAL DATA: Characterization data near this site (S73 Oreg-6-(1-7)) completed at SCS lab at Riverside, California.
National Cooperative Soil Survey
U.S.A.