LOCATION OCUD NVTentative Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Lithic Argixerolls
TYPICAL PEDON: Ocud extremely gravelly sandy loam--forestland. (Colors are for dry soil unless otherwise noted.) The soil surface is covered with about 75 percent pebbles, 10 percent cobbles, and less than 1 percent stones.
A1--0 to 5 inches; grayish brown (10YR 5/2) extremely gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; few very fine roots; many fine and medium interstitial pores; 85 percent pebbles and 5 percent cobbles; slightly acid (pH 6.2); clear wavy boundary. (2 to 5 inches thick)
A2--5 to 10 inches; brown (10YR 5/3) extremely gravelly loam, dark brown (10YR 3/3) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; common very fine and fine roots; common very fine and fine interstitial and common very fine tubular pores; 60 percent pebbles; slightly acid (pH 6.5); clear wavy boundary. (2 to 5 inches thick)
Bt--10 to 13 inches; pale brown (10YR 6/3) extremely gravelly sandy loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; very hard, friable, slightly sticky and slightly plastic; few very fine through coarse roots; common very fine tubular and interstitial pores; 60 percent pebbles; common faint clay films on faces of peds; slightly acid (pH 6.2); clear irregular boundary. (3 to 6 inches thick)
R--13 inches; hard fractured altered volcanic rock; fractured in the upper 4 inches.
TYPE LOCATION: Douglas County, Nevada; in the southern Pine Nut Mountains about 1.7 miles southeast of Carters Station; about 700 feet north and 650 feet west of the southeast corner of section 10, T. 11 N., R. 21 E.; USGS Double Spring 7.5 minute topographic quadrangle; 38 degrees 49 minutes 33 seconds north latitude and 119 degrees 36 minutes 22 seconds west longitude, NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture - Usually moist in winter and spring, dry from July through October; aridic moisture regime that borders on xeric.
Mean annual soil temperature - 47 to 53 degrees F.
Mollic epipedon thickness - 7 to 12 inches; includes the Bt horizon in some pedons.
Depth to bedrock - 7 to 14 inches to a lithic contact.
Reaction - Slightly acid or neutral.
Particle-size control section - Clay content: Averages 15 to 25 percent; Rock fragments: 60 to 80 percent, mainly gravel. Lithology of fragments are volcanic rocks such as rhyolite or andesite.
A horizons - Chroma: 2 or 3, dry or moist.
Organic matter content: 1 to 3 percent.
Bt horizon - Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 or 3, dry or moist.
Texture: Extremely gravelly sandy loam or extremely gravelly sandy clay loam.
Clay content: 18 to 27 percent.
Rock fragments: 60 to 80 percent.
Consistence: Hard or very hard dry, very friable or friable moist.
Organic matter content: 1 or 2 percent.
COMPETING SERIES: These are the Argabak, Bellehelen, Brier, Canfire (T), Chinabutte, Clovercreek, Duco, Gwin, Horseflat, Orhood, Reywat, Shepridge (T), Stepmount (T), Upatad, and Windry series.
Argabak soils have mollic epipedons that are 5 to 7 inches thick. Bellehelen and Brier soils are moist for 10 to 20 days during the summer due to convection storms and have 35 to 60 percent rock fragments in the particle-size control section. In addition, Brier soils have lithic contacts at depths of 14 to 20 inches. Canfire, Chinabutte, Clovercreek, Gwin, Shepridge, Stepmount, and Windry soils have a xeric moisture regime. Duco soils have 27 to 35 percent clay in the particle-size control section. Horseflat soils have mollic epipedons 12 to 17 inches thick and have silica coating the lithic contact. Orhood soils have hue of 7.5YR. Reywat soils have accumulation of identifiable secondary carbonates above the bedrock contact. Upatad soils have 35 to 60 percent rock fragments in the particle-size control section, have horizons with identifiable secondary carbonates, and have lithic contacts at depths of 14 to 20 inches.
GEOGRAPHIC SETTING: Ocud soils are on mountains. These soils formed in residuum and colluvium derived from volcanic rocks. Slopes are 15 to 50 percent. Elevations range from 5,800 to 6,700 feet. The climate is semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 10 to 14 inches, mean annual temperature is 47 to 50 degrees F., and the frost-free period is 80 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Duco soil and the Nosrac soil. Nosrac soils are very deep.
DRAINAGE AND PERMEABILITY: Well drained; very high surface runoff; moderate permeability.
USE AND VEGETATION: Ocud soils are used for forestland and wildlife habitat. The present vegetation is mainly a forest canopy of singleleaf pinyon with an understory of mountain big sagebrush, green ephedra, antelope bitterbrush, and desert needlegrass.
DISTRIBUTION AND EXTENT: Western Nevada. These soils are not extensive. MLRA 26.
MLRA OFFICE RESPONSIBLE: Reno, Nevada.
SERIES PROPOSED: Douglas County, Nevada, 1996. The name is coined.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 10 inches (A1 and A2 horizons).
Argillic horizon - The zone from 10 to 13 inches (Bt horizon).
Lithic contact - The boundary at 13 inches to hard bedrock (R layer).
Particle-size control section - The zone from the soil surface to 13 inches (A1, A2, and Bt horizons).