LOCATION MOPANG WAEstablished Series
TAXONOMIC CLASS: Medial, ferrihydritic, isomesic Typic Fulvudands
TYPICAL PEDON: Mopang medial silt loam, forested; on a northeast facing 25 percent slope under a western hemlock forest at 80 feet elevation. (Colors are for moist soil unless otherwise stated. All textures are apparent field textures.)
Oi--0 to 2 inches; slightly decomposed accumulation of western hemlock needles, twigs and mosses.
Oa--2 to 4 inches; highly decomposed needles and twigs. (1 to 6 inches thick, combined O horizons)
A--4 to 10 inches; dark reddish brown (5YR 3/2) medial silt loam, brown (7.5YR 4/4) dry; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic and weakly smeary; many fine, medium and coarse roots; many fine interstitial pores; 5 percent rounded gravel; extremely acid (pH 4.0); clear wavy boundary. (3 to 8 inches thick)
Bw1--10 to 25 inches; dark reddish brown (5YR 3/4) medial silty clay loam, brown (7.5YR 5/4) dry; weak fine and medium subangular blocky structure; hard, firm, moderately sticky and slightly plastic and weakly smeary; common fine, medium and coarse roots; many fine tubular pores; 5 percent rounded gravel; extremely acid (pH 4.4); gradual wavy boundary. (14 to 18 inches thick)
Bw2--25 to 47 inches; brown (7.5YR 4/4) medial silty clay loam, reddish yellow (7.5YR 6/6) dry; weak fine and medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic and weakly smeary; few fine and medium roots; common fine tubular pores; 10 percent rounded gravel; very strongly acid (pH 4.6); clear wavy boundary. (21 to 25 inches thick)
2Bw3--47 to 55 inches; strong brown (7.5YR 5/6) very gravelly silt loam, reddish yellow (7.5YR 6/6) dry; massive; hard, firm, slightly sticky and slightly plastic and weakly smeary; few fine tubular pores; 40 percent rounded gravel; very strongly acid (pH 4.6); clear smooth boundary. (7 to 9 inches thick)
2Bsm--55 to 64 inches; strong brown (7.5YR 5/6) dense glacial drift that crushes to extremely gravelly medial silt loam, brownish yellow (10YR 6/6) dry; massive; very hard, very firm, slightly sticky and slightly plastic; weakly cemented by iron and manganese; 65 percent rounded gravel; very strongly acid (pH 4.6).
TYPE LOCATION: Grays Harbor County, Washington; 8 miles northwest of Hoquiam; along Bodey Loop Road (ITT Rayonier Road Number 4012), 2 miles from intersection with Ocean Beach Road; 800 feet east and 600 feet south of the NW corner section 24, T.18N., R.11W.
RANGE IN CHARACTERISTICS: Depth to very gravelly 2Bw horizon is 40 to 50 inches with cemented glacial till within 60 inches. Densic material can underlie the cemented material. Moist hue is 5YR to 10YR. The soil is extremely acid or very strongly acid. The particle size control section is medial silt loam or medial silty clay loam, has 5 to 15 percent rounded coarse fragments and 25 to 35 field estimated percent clay. The mean annual soil temperature is 47 to 51 degrees F. The difference between mean summer and mean winter soil temperature is 5 to 9 degrees F. The A and Bw horizons have andic soil properties with moist bulk density is 0.75 to 0.90 g/cc., and oxalate aluminum plus one-half the iron is 2 to 4 percent and phosphate retention is 85 to 100 percent. Acid oxalate iron is 1.5 to 3.0 percent. 15-bar water is 20 to 35 percent on air-dried samples.
The A horizon has value of 3 to 5 dry, and chroma of 2 or 3 moist and 3 or 4 dry. It has 10 to 25 percent organic matter. It has 5 to 15 cmol/kg of aluminum.
The Bw horizon has value of 3 to 5 moist, 5 to 7 dry, and chroma of 4 to 6. It is medial silty clay loam or medial silt loam. This horizon has weak or moderate structure. It has 4 to 10 percent organic matter and is less than 7 percent below 20 inches. It has 2 to 5 cmol/kg of aluminum.
The 2Bw horizon has value of 3 to 5 moist, 5 to 7 dry, and chroma of 4 to 6. It is very gravelly silt loam or extremely gravelly silt loam. The moist bulk densit if 0.90 to 1.20 g/cc.
COMPETING SERIES: These are the Calawah, Ilwaco, Klootchie, Knappton, Lint, Lytell, Narel, Neotsu, Neskowin, Newskah, Palix, Queets and Salander series. Calawah, Ilwaco, Lint, Newskah, Queets and Salander soils are very deep. Klootchie soils are over 40 inches deep to a paralithic contact. Knappton soils are over 40 inches deep to a lithic contact. Lytell, Narel and Palix soils are 40 to 60 inches deep to a paralthic contact. Neotsu soils are 20 to 40 inches deep to a paralithic contact. Neskowin soils are 20 to 40 inches deep to a lithic contact.
GEOGRAPHIC SETTING: Mopang soils are on ground moraines and outwash terraces on till plains. These soils formed in glaciofluvial sediments. Slopes range from 5 to 90 percent. Elevation ranges from near sea level to 1,000 feet. They are in a humid marine climate with cool, wet winter and cool, moist summers. The annual precipitation ranges from 80 to 175 inches. The mean January temperature is 38 degrees F.; the mean July temperature is 60 degrees F.; and the mean annual temperature is 48 degrees F. The frost-free period is 140 to 220 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Copalis, Hoko, Nemah, Southshore and Wishkah soils. Nemah soils are poorly drained. Copalis soils have the cemented till at 20 to 40 inches. Southshore soils are medial-skeletal and have the cemented till at 40 to 60 inches. Hoko soils are medial-skeletal and have the cemented till at 20 to 40 inches. Wishkah soils are somewhat poorly drained.
DRAINAGE AND PERMEABILITY: Well or moderately well drained; slow to rapid runoff; moderate permeability to the cemented till and very slow through it. There is a seasonal zone of saturation between 3.5 and 5.0 feet from November through April.
USE AND VEGETATION: Principal uses are timber production, watershed, wildlife habitat and recreation. Vegetation is primarily a western hemlock forest with scattered western red cedar and Sitka spruce. Understory species include western swordfern, western brachenfern, salal, red huckleberry, salmonberry, vine maple, and cascara.
DISTRIBUTION AND EXTENT: Grays Harbor County; Washington MLRA 4A. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Grays Harbor County, Washington, 1979.
REMARKS: Diagnostic horizons and other features:
The map units that are correlated as a cool phase and characterized by having Pacific silver fir in the plant community need to be re-correlated to a series that is isofrigid. The mesic counterpart of this series (Mopang) is the Hoquiam series.
- Ochric epipedon
- Cambic horizon - 10 to 55 inches
- Organic carbon is less than 4 percent below 20 inches.
- Andic soil properties - 4 to 47 inches
- All depths to diagnostic horizons and features are measured from the top of the first mineral horizon.
ADDITIONAL DATA: National Soil Survey Laboratory, Lincoln, Nebraska; data is available on the soil: Sample Number S78WA-27-2. Depth sampled are 8 to 15 inches, 25 to 30 inches and 38 to 42 inches. Sample Number S98WA-027-004 is complete characterization. Sample Number S89WA-31-003 complete characterization.