LOCATION ITCA NV+ID OREstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Lithic Argixerolls
TYPICAL PEDON: Itca extremely stony loam--forestland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 6 inches; grayish brown (10YR 5/2) extremely stony loam, very dark grayish brown (10YR 3/2) moist; weak thick platy structure parting to weak very fine granular; slightly hard, very friable, slightly sticky and nonplastic; many very fine and few fine roots; many fine interstitial pores; 30 percent gravel, 15 percent cobbles, and 15 percent stones; neutral (pH 7.2); clear wavy boundary. (1 to 7 inches thick)
A2--6 to 9 inches; brown (10YR 5/3) gravelly sandy loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium roots; common fine interstitial pores; 20 percent gravel and 5 percent cobbles; slightly alkaline (pH 7.4); abrupt wavy boundary. (0 to 6 inches thick)
Bt1--9 to 13 inches; pale brown (10YR 6/3) very gravelly clay loam, brown (10YR 4/3) moist; weak medium prismatic structure parting to moderate medium subangular blocky; slightly hard, friable, very sticky and very plastic; common fine and few medium and coarse roots; common fine interstitial pores; many faint clay films lining pores and on faces of peds; 25 percent gravel and 15 percent cobbles; slightly alkaline (pH 7.4); clear irregular boundary. (3 to 9 inches thick)
Bt2--13 to 17 inches; light yellowish brown (10YR 6/4) very cobbly clay, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure; hard, firm, very sticky and very plastic; few fine, medium and coarse roots; few fine tubular pores; common distinct clay films lining pores and on faces of peds; 20 percent gravel, 20 percent cobbles, and 10 percent stones; slightly alkaline (pH 7.4); abrupt broken boundary. (3 to 10 inches thick)
R--17 inches; hard, fractured andesite.
TYPE LOCATION: Lander County, Nevada; about 22 miles east of Austin; approximately 1,950 feet east and 320 feet south of the northwest corner of section 21, T. 2 S., R. 40 E.; USGS Hickison Summit 7.5 minute topographic quadrangle; latitude 39 degrees 28 minutes 30.74 seconds N. and longitude 116 degrees 44 minutes 38.29 seconds W., NAD83.
RANGE IN CHARACTERISTICS:
Soil moisture - Moist in winter and spring, dry 60 to 90 consecutive days July through October; Xeric moisture regime that borders on aridic.
Mean annual soil temperature - 42 to 47 degrees F.
Mollic epipedon thickness - 7 to 15 inches; includes the Bt1 horizon in some pedons.
Depth to bedrock - 10 to 20 inches to a lithic contact.
Other features - Abrupt boundaries exist between the A and Bt horizons.
A horizon
Hue: 7.5YR or 10YR.
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3.
Reaction: Neutral or slightly alkaline.
Bt horizons
Hue: 7.5YR or 10YR.
Value: 4 through 6 dry and 3 or 4 moist.
Chroma: 2 through 4.
Texture: Clay or clay loam.
Clay content: 35 to 45 percent when averaged; some subhorizons range up to 50 percent clay.
Structure: Platy, prismatic, or subangular blocky.
Rock fragments: 35 to 60 percent, when averaged, mainly gravel and cobbles; some subhorizons range up to 85 percent.
Consistence: Slightly hard or hard dry, friable or firm moist, and moderately sticky or very sticky wet.
Reaction: Neutral to moderately alkaline.
Other features: Some pedons have thin BC or C horizons consisting primarily of very soft decomposing bedrock yielding pararock fragments; In shallower pedons, the Bt horizon tongues into fractures in the bedrock contact.
COMPETING SERIES: These are the Ateron, Camool (T), Canest (T), Chen, Douhide, Graley, Harlow, Vennob, and Wallsburg series.
Ateron soils do not have prismatic structure in the argillic horizon. Camool soils have mollic epipedons that include the entire argillic horizon and have more than 3 percent organic matter in the A horizons. Canest soils are very shallow and the mollic epipedon extends to the lithic contact. Chen, Douhide, and Graley soils have an aridic moisture regime bordering on xeric. Harlow soils have mollic colors throughout the Bt horizon and also do not have prismatic structure in the argillic horizon. Vennob soils do have abrupt boundaries between the A and Bt horizons. Wallsburg soils do not have prismatic structure in the argillic horizon and contain rock fragments that are dominantly sandstone and limestone.
GEOGRAPHIC SETTING: Itca 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 6,000 to 8,500 feet in Nevada. They range as low as 4,600 feet in Idaho on north aspects and 5,000 feet in Oregon. The climate is semiarid with cold, moist winters and warm, dry summers. The mean annual precipitation is 12 to 18 inches, the mean annual temperature is 40 to 46 degrees F., and the frost-free period is 50 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Borealis, Ravenswood, Softscrabble, and Walti soils. Borealis soils have an ochric epipedon and an indurated duripan at depths of 20 to 35 inches. Ravenswood and Walti soils have a lithic contact at depths of 20 to 40 inches. Softscrabble soils are very deep and loamy-skeletal.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Itca soils are used for forestland, rangeland, and wildlife habitat. The present vegetation is mainly a forest canopy of singleleaf pinyon and Utah juniper with an understory of mountain big sagebrush, Idaho fescue, antelope bitterbrush, and grasses.
DISTRIBUTION AND EXTENT: Central and western Nevada, southern Idaho, and southwestern Oregon. These soils are extensive. The series concept and main acreage is in MLRA 28B, while other acreage occurs in MLRAs 21, 24, 25, and 27.
MLRA OFFICE RESPONSIBLE: Reno, Nevada.
SERIES ESTABLISHED: Lincoln County, Nevada (Meadow Valley Area), 1981.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 9 inches (A1 and A2 horizons).
Argillic horizon - The zone from 9 to 17 inches (Bt1 and Bt2 horizons).
Lithic contact - The boundary at 17 inches to underlying hard bedrock (R layer).
Particle-size control section - The zone from 9 to 17 inches (Bt1 and Bt2 horizons).