LOCATION DOUGAN WAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, isotic, frigid Andic Dystrudepts
TYPICAL PEDON: Dougan very gravelly loam - forested. (Colors are for moist soil unless otherwise noted.)
Oi-0 to 1 inch; slightly decomposed leaves, twigs, and needles.
A--1 to 12 inches; very dark grayish brown (10YR 3/2) very gravelly medial loam, grayish brown (10YR 5/2) dry; weak, fine granular structure; slightly hard, friable, nonsticky, nonplastic and weakly smeary; common very fine, fine and medium roots; many fine irregular pores; 40 percent pebbles, 10 percent cobbles; strongly acid; (pH 5.4); clear wavy boundary. (10 to 12 inches thick)
2Bw--12 to 25 inches; light olive brown (2.5Y 5/3) very gravelly loam, light yellowish brown (2.5Y 6/3) dry; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky, and slightly plastic; few very fine and fine roots; common fine irregular and common fine tubular pores; 30 percent pebble, 10 percent cobbles and 10 percent saprolitic pebbles; strongly acid (pH 5.2); clear smooth boundary. (12 to 13 inches thick)
2C--25 to 40 inches; light yellowish brown (2.5Y 6/3) extremely gravelly loam, pale yellow (2.5Y 7/3) dry; weak granular structure; slightly hard, friable, slightly sticky, and slightly plastic; few fine roots; few fine irregular pores; 50 percent pebbles, 15 percent cobbles and 15 percent saprolitic pebbles; very strongly acid (pH 5.0); clear wavy boundary. (8 to 15 inches thick)
2R--40 inches; fractured andesite.
TYPE LOCATION: Skamania County, Washington; 600 feet south, 900 feet west of the northeast corner, sec. 27, T. 3 N., R. 5 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 43 degrees to 47 degrees F. Depth to a lithic contact is 30 to 40 inches. These soils are usually moist and are dry for less than 45 consecutive days in the summer in all parts of the moisture control section. The control section averages 45 to 70 percent rock fragments and 10 to 20 percent saprolitic fragments. The umbric epipedon ranges from 10 to 12 inches in thickness and is influenced by volcanic ash.
The A horizon has value of 2 or 3 moist, 4 or 5 dry, and chroma of 1 or 2 moist, 1 to 3 dry. Pebbles range from 30 to 40 percent and cobbles from 5 to 10 percent. Reaction is strongly acid or moderately acid.
The B horizon has hue of 10YR or 2.5Y, value of 4 or 5 moist, 5 or 6 dry, and chroma of 3 or 4 moist or dry. Pebbles range from 30 to 40 percent, cobbles from 5 to 20 percent and saprolitic fragments from 5 to 30 percent. It is very gravelly loam, very gravelly silt loam, very cobbly loam, or very cobbly silt loam. Reaction is very strongly acid or strongly acid.
The C horizon has hue of 10YR or 2.5Y, value of 5 or 6 moist, 6 or 7 dry, and chroma of 3 to 5 moist or dry. Pebbles range from 45 to 55 percent, cobbles from 15 to 30 percent and saprolitic fragments from 5 to 15 percent. It is extremely gravelly loam or extremely cobbly loam. Reaction is very strongly acid or strongly acid.
COMPETING SERIES: These are the Dobbs, Fernwood and Zygore series. Dobbs soils have a paralithic contact with dense glacial till at 30 to 40 inches. Fernwood soils lack saprolite, have 10 to 20 percent pebbles and 25 to 50 percent cobbles in the particle-size control section. Zygore soils are more than 40 inches deep.
GEOGRAPHIC SETTING: Dougan soils are on backslopes and ridgetops of mountains at elevations of 2,000 to 3,000 feet. Slopes are 5 to 65 percent. These soils formed in colluvium from andesite and granodiorite with an admixture of volcanic ash in the upper part. Summers are cool and moist. Winters are cold and wet with snow cover from December through March. Mean annual precipitation is 90 to 110 inches. Mean January temperature is about 25 degrees F; mean July temperature is about 62 degrees F. Mean annual temperature is 41 to 45 degrees F. Frost-free season is 90 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Kinney, Olyic, and Skoly soils. Kinney soils are fine-loamy and mesic. Olyic soils are in the fine-loamy family and have an argillic horizon. Skoly soils have hue of 7.5YR or redder and are mesic.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Used primarily for timber production, recreation, and wildlife habitat. Vegetation is Douglas-fir and western hemlock, with an understory of vine maple, red huckleberry, big huckleberry, serviceberry, Oregon-grape, pachystima, longtube twinflower, false-Solomons-seal, insideout flower, American starflower, Oregon fairybells, Oregon oxalis, bunchberry dogwood, creambush oceanspray, and deerfoot vanillaleaf.
DISTRIBUTION AND EXTENT: Southwestern Washington. The series is of small extent.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Skamania County, Washington, 1981.
REMARKS: Diagnostic horizons and features recognized in this pedon are: an umbric epipedon from the mineral surface to 12 inches, a cambic horizon from 12 to 40 inches, and a lithic contact at 40 inches. The bulk density is assumed to be less than 0.95 g/cc in the upper 7 to 14 inches and between 0.85 and 1.10 in most of the particle-size control section. The zone between 1 and 12 inches is assumed to have andic soil properties and is based on lab data from similar soils (S98WA-059-001). The 15-bar moisture is estimated to be 15 to 20 percent (air-dry), acid oxalate aluminum plus one-half iron of 1 to 3 percent; phosphate retention of 75 to 85 percent, and volcanic glass content of 5 to 30 percent.
This draft reflects a change in classification from medial-skeletal, frigid Andic Haplumbrepts to loamy-skeletal, isotic, frigid Andic Dystrudepts. Additional data on andic properties is needed on this series to confirm classification of andic subgroup or andisol. Classification changed 6/98 based on 1998 Keys to Soil Taxonomy. Competing series not revised.