LOCATION OLAC NV+CA OREstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Lithic Xeric Haplargids
TYPICAL PEDON: Olac very stony loam--rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 5 cm; brown (10YR 5/3) very stony loam, dark brown (10YR 3/3) moist; strong very fine granular structure; soft, very friable, slightly sticky and slightly plastic; common very fine roots; few very fine tubular pores; 30 percent gravel and 20 percent stones; slightly alkaline (pH 7.6); abrupt smooth boundary. (3 to 8 cm thick)
A2--5 to 8 cm; brown (10YR 5/3) very gravelly loam, dark brown (10YR 3/3) moist; strong thick platy structure; slightly hard, very friable, moderately sticky and moderately plastic; common very fine roots; many very fine vesicular pores; 35 percent gravel; slightly alkaline (pH 7.6); abrupt wavy boundary. (3 to 8 cm thick)
Bt--8 to 25 cm; very pale brown (10YR 7/3) extremely gravelly loam, brown (10YR 4/3) moist; weak coarse subangular blocky structure; slightly hard, firm, moderately sticky and moderately plastic; few very fine, fine and medium roots; few faint clay films on faces of peds and lining pores; 60 percent gravel; slightly alkaline (pH 7.6); abrupt irregular boundary. (13 to 25 cm thick)
R--25 cm; fractured andesite.
TYPE LOCATION: Douglas County, Nevada; on the Toiyabe National Forest in the Wellington Hills about 3 miles southeast of Wellington; approximately 800 feet north and 150 feet west of the southeast corner of section 13, T. 10 N., R. 23 E.; USGS Desert Creek Ranch 7.5 minute topographic quadrangle; latitude 38 degrees 43 minutes 29 seconds N and longitude 119 degrees 21 minutes 1 seconds W; NAD 83.
RANGE IN CHARACTERISTICS:
Soil moisture - Usually dry summer and fall, moist November through early June; Aridic moisture regime that borders on xeric.
Mean annual soil temperature - 8 to 11 degrees C.
Depth to bedrock - 20 to 36 cm to a lithic contact.
Reaction - Slightly acid to slightly alkaline.
Particle-size control section - Clay content: 18 to 27 percent.
Rock fragments: 35 to 65 percent, mainly angular gravel with 0 to 30 percent cobbles or stones in the upper part. Lithology of fragments are volcanic rocks such as andesite, basalt, and rhyolite.
A horizons - Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 or 3, dry or moist.
Rock fragments: 20 to 65 percent.
Bt horizon - Hue: 7.5YR or 10YR.
Value: 4 through 7 dry, 3 or 4 moist.
Chroma: 2 through 4, dry or moist.
Texture: Extremely gravelly loam or extremely gravelly clay loam.
Consistence: Friable or firm; slightly sticky or moderately sticky and slightly plastic or moderately plastic.
Clay content: 23 to 30 percent.
Rock fragments: 60 to 75 percent, mainly pebbles.
COMPETING SERIES: These are the Atlow, Boomstick, Checkett, Chubard, Cottle, Fortyday, Gabbvally, Hooplite, Nevo, Old Camp, Phliss, Rowel, Soughe, Stewval, and Thike series.
Atlow soils have 35 to 50 percent rock fragments in the argillic horizon. Cubard, Cottle, Phliss, and Old Camp soils have identifiable secondary carbonates in the lower part of the argillic horizon. Boomstick and Fortyday soils are 36 to 50 cm to bedrock. Checkett soils are calcareous in all parts. Gabbvally soils have 35 to 50 percent rock fragments in the argillic horizon. Hooplite soils are calcareous. Nevo soils have secondary silica coats on the lithic contact. Rowel soils have argillic horizons with 40 to 55 percent clay. Soughe soils have 35 to 60 percent rock fragments in the argillic horizon. Stewval soils are calcareous throughout, have mean annual soil temperature of 12 to 15 degrees C., and are intermittently moist in some part of the soil moisture control section for 10 to 20 days cumulative between July and October. Thike soils average 12 to 18 percent clay in the particle-size control section, have more than half 2 to 5 millimeter gravel, and the sand fraction is dominated by coarse sand.
GEOGRAPHIC SETTING: Olac soils are on hills, mountains, and plateaus. They formed in residuum and colluvium derived from volcanic rocks. Slopes are 2 to 75 percent. Elevations range from 1,280 to 1,980 meters. The climate semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 200 to 300 mm, the mean annual temperature is 7 to 9 degrees C., and the frost-free period is 80 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Duco, Loomis, Nosrac, Surgem, and Zephan soils. Duco soils are loamy-skeletal, shallow to lithic contacts, and have mollic epipedons and argillic horizons. Loomis soils are clayey-skeletal, very shallow and shallow to lithic contacts, and have argillic horizons. Nosrac soils are loamy-skeletal, very deep, and have mollic epipedons and argillic horizons. Surgem and Zephan soils are clayey-skeletal, moderately deep to bedrock, and have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; very high surface runoff; moderate permeability; moderately high or high saturated hydraulic conductivity.
USE AND VEGETATION: Olac soils are used for livestock grazing and wildlife habitat. The present vegetation is mainly low sagebrush, Sandberg's bluegrass, and desert needlegrass.
DISTRIBUTION AND EXTENT: Western and northern Nevada, eastern California, and southeastern Oregon. These soils are moderately extensive. The series concept and main acreage is in MLRA 26, while other acreage occurs in MLRAs 24, 25, and 27.
MLRA OFFICE RESPONSIBLE: Reno, Nevada.
SERIES ESTABLISHED: Douglas County Area, Nevada, 1981.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 8 cm (A1 and A2 horizons).
Argillic horizon - The zone from 8 to 25 cm (Bt horizon).
Lithic contact - The boundary at 25 cm to underlying hard bedrock (R layer).
Particle-size control section - The zone from the soil surface to 25 cm (A1, A2, and Bt horizons).