LOCATION SITKUM OREstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Typic Dystroxerepts
TYPICAL PEDON: Sitkum sandy loam - forested, on a 75 percent north slope at an elevation of 1700 feet. (Colors are moist unless otherwise stated)
Oi--1 inch to 0; partially decomposed needles, leaves and twigs.
A1--0 to 4 inches; dark brown (7.5YR 3/3) sandy loam, yellowish brown (10YR 5/4) dry; moderate very fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine, common fine and medium and few coarse roots; many very fine irregular pores; 5 percent gravel; neutral (pH 7.0); clear smooth boundary.
A2--4 to 12 inches; strong brown (7.5YR 4/6) sandy loam, brown (7.5YR 5/4) dry; moderate very fine and fine granular structure; slightly hard, very friable, nonsticky and nonplastic; common very fine, fine and medium and few coarse roots; many very fine irregular pores; 5 percent gravel; neutral (pH 6.8); gradual wavy boundary (Combined thickness of the A horizon is 6 to 12 inches)
Bw1--12 to 24 inches; strong brown (7.5YR 4/6) sandy loam, light brown (7.5YR 6/4) dry; weak fine and medium subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common very fine and few fine, medium, and coarse roots; common very fine tubular pores; 10 percent gravel; slightly acid (pH 6.5); gradual wavy boundary.
Bw2--24 to 38 inches; strong brown (7.5YR 4/6) sandy loam, light brown (7.5YR 6/4) dry; weak medium and coarse subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; few very fine, fine, medium, and coarse roots; common very fine tubular pores; 10 percent gravel; moderately acid (pH 5.6); clear wavy boundary. (Combined thickness of the Bw horizon is 14 to 28 inches)
Cr--38 inches; partially decomposed granodiorite.
TYPE LOCATION: Douglas County, Oregon, about 2 miles southwest of Riser Butte and about 850 feet north and 600 feet west of the southeast corner of section 25, T. 28 S., R. 4 W. W.M. (Latitude 43 degrees, 6 minutes, 3 seconds N, Longitude 123 degrees, 6 minutes, 39 seconds W)
RANGE IN CHARACTERISTICS: The soils are usually moist and are dry for 45 to 60 consecutive days between depths of approximately 8 and 24 inches during the 4 month period following summer solstice. The mean annual soil temperature is 47 to 54 degrees F. Depth to bedrock is 20 to 40 inches. Hue is 10YR or 7.5YR. The particle-size control section averages 12 to 18 percent clay and 15 percent or more sand that is coarser than very fine sand.
The A horizon has value of 3 or 4 moist, 5 or 6 dry, and chroma of 3 to 6 moist and dry. It has 0 to 10 percent gravel. It is slightly acid or neutral.
The Bw horizon has value of 4 or 5 moist, 6 or 7 dry, and chroma of 4 to 6 moist and dry. It is sandy loam, loam, or gravelly sandy loam with 12 to 18 percent clay. It has 0 to 20 percent gravel. It is moderately acid or slightly acid.
COMPETING SERIES: These are the Chaix, Dome, Siskiyou, Steinmetz, Tethrick and Ulricher series. Chaix soils are dry for more than 90 consecutive days. Siskiyou soils are dry for 60 to 90 consecutive days. Dome, Tethrick, and Ulricher soils are over 40 inches deep to bedrock. Steinmetz soils are over 60 inches deep to bedrock.
GEOGRAPHIC SETTING: Sitkum soils are on mountain side slopes. The soils formed in colluvium and residuum weathered from granitic rocks. Slopes are 30 to 90 percent. Elevations are 1000 to 3300 feet. The climate is characterized by warm, wet winters and hot, dry summers. The mean annual temperature is 45 to 52 degrees F. The mean annual precipitation is typically 40 to 60 inches but may range to 100 inches in high winter rainfall interior mountains of Curry County, Oregon. The frost-free period is 100 to 180 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Beal, Buckshot, Lettia, Sharpshooter, Stinger, Zing and competing Steinmetz soils. Steinmetz soils are associated with Sitkum soils on less steeply sloping, more stable positions. Buckshot and Stinger soils have a udic moisture regime and are on adjacent north slopes. Lettia soils are fine-loamy and on less steeply sloping, more stable hill slopes. Sharpshooter soils are fine-loamy and derived from mica schists. Zing soils are somewhat poorly drained. Beal soils are moderately well drained. Beal and Zing soils are on foot slopes and in concave areas on side slopes.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; moderately rapid permeability.
USE AND VEGETATION: Sitkum soils are used for timber production and wildlife habitat. Native vegetation includes Douglas fir, incense cedar, ponderosa pine, and Pacific madrone with an understory of salal, cascade Oregongrape, golden chinkapin, western swordfern, creambush oceanspray, western hazel and Pacific poison oak.
DISTRIBUTION AND EXTENT: Southwestern Oregon, MLRA 5. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Douglas County, Oregon, 1994.
REMARKS: Formerly classified as coarse-loamy, mixed, mesic Dystric Xerochrepts, competing series not updated at the time of reclassification.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon
Cambic horizon - from 12 to 38 inches (Bw1 and Bw2 horizons)
Particle-size control section - from 10 to 38 inches
Dystric subgroup - base saturation (by ammonium acetate) between the depths of 10 and 30 inches is assumed to be less than 60 percent based on geographically associated soils.