LOCATION HART OREstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Duric Palexerolls
TYPICAL PEDON: Hart very gravelly loam--rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 9 inches; brown (7.5YR 4/2) very gravelly loam, dark brown (7.5YR 3/2) moist; strong fine granular structure; loose, very friable, slightly sticky and nonplastic; many fine and very fine roots; 5 percent cobbles and 40 percent gravel; slightly alkaline (pH 7.4); abrupt smooth boundary. (4 to 12 inches thick)
2Bt--9 to 19 inches; brown (7.5YR 4/4) clay, brown (7.5YR 4/4) moist; strong fine prismatic structure; very hard, firm, very sticky and plastic; few very fine roots; few very fine irregular pores; 5 percent fine gravel; many distinct clay films on faces of peds and lining pores; slightly alkaline (pH 7.6); gradual wavy boundary. (8 to 18 inches thick)
3Bk1--19 to 25 inches; pink (7.5YR 7/4) very gravelly silty clay loam, brown (7.5YR 4/4) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; 5 percent cobbles and 40 percent fine gravel; violently effervescent;, secondary carbonates segregated in many fine filaments and irregularly shaped masses; moderately alkaline (pH 8.2); gradual wavy boundary. (5 to 10 inches thick)
3Bk2--25 to 30 inches; pinkish gray (7.5YR 7/2) very gravelly loam, brown (7.5YR 4/4) moist; massive; hard, very firm, slightly sticky and nonplastic; 5 percent cobbles and 30 percent fine gravel; strongly effervescent; secondary carbonates are finely disseminated in the matrix; moderately alkaline (pH 8.0); abrupt smooth boundary. (5 to 10 inches thick)
3Bkq--30 to 43 inches; pale brown (10YR 6/3) extremely gravelly loam, brown (10YR 4/3) moist; massive; very hard, very firm and brittle, nonsticky and nonplastic; 5 percent cobbles and 60 percent gravel; strongly effervescent; secondary carbonates are finely disseminated in the matrix and coat rock fragments; moderately alkaline (pH 8.0); abrupt irregular boundary. (5 to 15 inches thick)
4R--43 inches; fractured tuff; opaline silica and calcium carbonate line widely-spaced fractures.
TYPE LOCATION: Lake County, Oregon; between Deppy Creek and McDowell Creek and east of the powerline; in the NE 1/4, of the NW 1/4, of the SE 1/4 of section 1, T. 37 S., R. 22 E.; USGS Drake Peak NE 7.5 minute topographic quadrangle; approximately 42 degrees 23 minutes 15 seconds north latitude and 120 degrees 04 minutes 01 seconds west longitude, NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture - These soils are dry for more than half the time when the soil temperature is greater than 41 degrees F. The soil temperature is above 41 degrees F. from about March 15 to November 15; aridic moisture regime that borders on xeric.
Mean annual soil temperature - 45 to 47 degrees F.
Mollic epipedon thickness - 7 to 12 inches; does not include the 2Bt horizon.
Depth to base of argillic horizon - 15 to 30 inches.
Depth to horizons with secondary carbonates - 15 to 30 inches.
Depth to horizon with firm, brittle consistence or durinodes - 30 to 40 inches.
Depth to bedrock - 40 to 60 inches to a lithic contact.
Particle-size control section - Clay content: 45 to 55 percent; Rock fragments: 5 to 25 percent, mainly fine gravel. Lithology of fragments are volcanic rocks such as basalt and tuff.
Other features - An abrupt horizon boundary is normally present between the A and the 2Bt horizon accompanied by an abrupt increase in clay content of 20 to 40 percent.
A horizon - Hue: 7.5YR or 10YR.
Value: 4 or 5 dry, 2 or 3 moist.
Texture: Extremely cobbly loam or very gravelly loam.
Clay content: 15 to 25 percent.
Rock fragments: 10 to 50 percent gravel, 5 to 50 percent cobbles.
Organic matter content: 1 to 3 percent.
2Bt horizon - Hue: 7.5YR or 10YR.
Value: 4 or 5 dry, 3 or 4 moist.
Chroma: 3 or 4, dry or moist.
Texture: Clay or gravelly clay.
Clay content: 45 to 55 percent.
Rock fragments: 5 to 25 percent gravel, 0 to 5 percent cobbles.
Clay films: Common, distinct or prominent.
Structure: Strong fine prismatic to strong fine angular blocky.
3Bk horizons - Value: 5 through 7 dry, 3 or 4 moist.
Chroma: 2 through 4, dry or moist.
Texture: Very gravelly silty clay loam, very gravelly loam, or gravelly loam.
Clay content: 15 to 35 percent.
Rock fragments: 20 to 40 percent mainly fine gravel, 0 to 5 percent cobbles.
Effervescence: Slightly effervescent through violently effervescent.
Calcium carbonate equivalent: 1 or 2 percent.
3Bkq horizon - Value: 3 or 4 moist.
Chroma: 3 through 6, dry or moist.
Texture: Very gravelly loam or extremely gravelly loam.
Clay content: 15 to 25 percent.
Rock fragments: 30 to 60 percent gravel, 5 to 10 percent cobbles.
Consistence: Firm or very firm and brittle when moist due to opaline silica.
Durinodes: Some pedons have 20 to 50 percent durinodes.
Calcium carbonate equivalent: 1 or 2 percent.
COMPETING SERIES: There are currently no other series in this family.
GEOGRAPHIC SETTING: Hart soils are on rock pediments on plateaus. These soils formed in alluvium over residuum derived from basalt and tuff. Slopes are 2 to 50 percent. Elevations range from 5,300 to 6,500 feet. The climate is semiarid and characterized by cool, moist winters and warm, dry summers. The mean annual precipitation is 12 to 16 inches, the mean annual temperature is 43 to 46 degrees F., and the frost-free period is 50 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Mascamp, Newlands, and Ninemile soils. Mascamp soils are loamy-skeletal and are shallow to lithic contacts. Newlands soils are fine-loamy and have a cryic temperature regime. Ninemile soils are shallow to lithic contacts.
DRAINAGE AND PERMEABILITY: Well drained; very high surface runoff; very slow permeability.
USE AND VEGETATION: Hart soils are used for livestock grazing and wildlife habitat. The vegetation is low sagebrush, Idaho fescue, and bluebunch wheatgrass. In areas with an A horizon less than 7 inches thick, the plant community is mainly black sagebrush, Sandberg's bluegrass, and bottlebrush squirreltail.
DISTRIBUTION AND EXTENT: South-central Oregon. These soils are moderately extensive. MLRA 23.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Lake County (Southern Part), Oregon, 1991.
REMARKS: This revision of February 2003 updates the taxonomic class from Fine, smectitic, frigid Aridic Palexerolls.
Diagnostic horizons and other features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 9 inches (A horizon).
Argillic horizon - The zone from 9 to 19 inches (2Bt horizon).
Palexerolls great group feature - The abrupt clay increase of more than 20 percent at 9 inches (between the A and 2Bt horizons).
Identifiable secondary carbonates - The zone from 19 to 43 inches (3Bk1, 3Bk2, and 3Bkq horizons).
Duric feature - The zone from 30 to 43 inches (3Bkq horizon).
Lithic contact - The boundary at 43 inches to underlying hard, unweathered bedrock (4R layer).
Particle-size control section - The zone from 9 to 19 inches (2Bt horizon).