LOCATION FOURWHEEL OREstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Xeric Paleargids
TYPICAL PEDON: Fourwheel clay loam--on an 8 percent slope--rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 2 inches; gray (10YR 6/1) clay loam, very dark grayish brown (10YR 3/2) moist; weak medium platy structure parting to weak medium subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine, and medium roots; many very fine and fine tubular and vesicular pores; 2 percent cobbles and 10 percent gravel; neutral (pH 7.0); clear wavy boundary. (2 to 5 inches thick)
A2--2 to 7 inches; light brownish gray (10YR 6/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine, fine, and medium roots; many very fine and fine tubular and irregular pores; 10 percent gravel; neutral (pH 7.0); abrupt wavy boundary. (5 to 9 inches thick)
Bt1-- 7 to 14 inches; dark yellowish brown (10YR 4/4) clay, dark yellowish brown (10YR 4/4) moist; strong medium subangular blocky structure; very hard, very firm, very sticky and very plastic; common very fine, fine, and medium roots; many very fine and fine tubular and irregular pores; many prominent clay films on faces of peds; 10 percent gravel; neutral (pH 7.2); abrupt wavy boundary.
Bt2--14 to 22 inches; yellowish brown (10YR 5/6) clay, yellowish brown (10YR 5/4) moist; moderate medium subangular blocky structure; very hard, very firm, very sticky and very plastic; few very fine and fine roots; many very fine irregular pores; common prominent clay films on faces of peds; 10 percent gravel; neutral (pH 7.3); gradual wavy boundary. (Combined thickness of the Bt horizons is 13 to 29 inches thick)
2R--22 inches; volcanic rock.
TYPE LOCATION: Harney County, Oregon; about 2.75 miles south of Whitehorse Road in the Trout Creek Mountains; approximately 2,100 feet north and 200 feet east of the southwest corner of section 28, T. 39 S., R. 37 E.; USGS Trout Creek Canyon 7.5 minute topographic quadrangle; 42 degrees 09 minutes 21 seconds north latitude and 118 degrees 23 minutes 14 seconds west longitude, NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture - The soils are dry for one-half to three-fourths of the time when the soil temperature is greater than 41 degrees F.; Aridic moisture regime that borders on xeric.
Mean annual soil temperature - 44 to 47 degrees F.
Mean summer soil temperature - 60 to 62 degrees F.
Ochric epipedon thickness - 7 to 14 inches.
Depth to base of argillic horizon - 20 to 40 inches.
Depth to bedrock - 20 to 40 inches to a lithic contact.
Particle-size control section - Clay content: Averages 45 to 60 percent; Rock fragments: 5 to 15 percent, mainly gravel.
Reaction - Neutral or slightly alkaline.
Other features - There is a 15 to 25 percent clay increase (absolute) between the A2 and Bt1 horizons.
A horizons - Value: 6 or 7 dry, 3 or 4 moist.
Chroma: 1 through 3, dry or moist.
Bt horizons - Value: 4 through 6 dry, 3 through 5 moist.
Chroma: 3 through 6 dry, 3 or 4 moist.
Texture: Clay or silty clay.
Other features: Some pedons have thin layers of clay loam or gravelly clay loam immediately above the bedrock and contains secondary carbonates.
COMPETING SERIES: These are the Coglin, Freznik, and Swaler series.
Coglin and Swaler soils are very deep. Freznik soils have 15 to 35 percent rock fragments in the particle-size control section and have an A horizons 2 to 7 inches thick.
GEOGRAPHIC SETTING: Fourwheel soils are on rock pediments, hills, and mountains. They typically occur on summit positions. These soils formed in slope alluvium and colluvium derived from volcanic rocks. Slopes are 3 to 40 percent. Elevations range from 4,200 to 6,500 feet. The climate is semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 10 to 12 inches, the mean annual temperature is 43 to 45 degrees F., and the frost-free period is 50 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lonely and Robson soils. Lonely soils have 27 to 35 percent clay in the particle-size control section and do not have an argillic horizon. Robson soils are clayey-skeletal and are shallow to a lithic contact.
DRAINAGE AND PERMEABILITY: Well drained; high surface runoff; very slow permeability.
USE AND VEGETATION: Fourwheel soils are used for rangeland. The vegetation commonly is Wyoming big sagebrush, bluebunch wheatgrass, Thurber's needlegrass, bottlebrush squirreltail, Sandberg's bluegrass, and Indian ricegrass.
DISTRIBUTION AND EXTENT: Southeastern Oregon. These soils are moderately extensive. MLRA 23.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Harney County, Oregon, 1997.
REMARKS: This revision of December 2004 updates the taxonomic class from Fine, smectitic, frigid Vertic Paleargids based on lack of vertic features in the typical pedon and calculated linear extensibility for the typical pedon that is less than 6.0 centimeters between the soil surface and the lithic contact.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 7 inches (A1 and A2 horizons).
Paleargids great group feature - The abrupt clay content increase of more than 15 percent at 7 inches (between the A2 and Bt1 horizons).
Argillic horizon - The zone from 7 to 22 inches (Bt1 and Bt2 horizons).
Lithic contact - The boundary at 22 inches to underlying hard, unweathered bedrock (2R layer).
Particle-size control section - The zone from 7 to 22 inches (Bt1 and Bt2 horizons).