LOCATION HOPBURN IDEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Vitrandic Haplocryalfs
TYPICAL PEDON: Hopburn silt loam, supporting a lodgepolepine/pinegrass community type, woodland; on an undulating slope of 3 percent on a south aspect, about 6,450 feet elevation. (Color is for air dry soil unless otherwise noted.)
Oi--1/2 to 0 inches; forest litter of needles and grass leaves; abrupt smooth boundary.
A--0 to 3 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak very fine granular structure; soft, very friable, nonsticky and slightly plastic; many very fine roots; many very fine irregular pores; strongly acid (pH 5.4); abrupt smooth boundary. (2 to 4 inches thick)
E1--3 to 11 inches; pale brown (10YR 6/3) silt loam, brown (10YR 5/3) moist; moderate coarse subangular blocky structure; hard, very friable, nonsticky and slightly plastic; many very fine and few fine, medium and coarse roots; many very fine tubular pores; moderately acid (pH 6.0); clear smooth boundary. (8 to 14 inches thick)
E2--11 to 21 inches; pale brown (10YR 6/3) silt loam, brown (10YR 5/3) moist; moderate very coarse subangular blocky structure; hard, very friable, nonsticky and slightly plastic; many very fine and few medium and coarse roots; many very fine tubular pores; trace stones; slightly acid (pH 6.4); clear smooth boundary. (0 to 12 inches thick)
Bt1--21 to 34 inches; light yellowish brown (10YR 6/4) loam, yellowish brown (10YR 5/4) moist; strong coarse subangular blocky structure parting to strong medium subangular blocky; hard, friable, sticky and plastic; few very fine and medium roots; few very fine tubular pores; continuous distinct uncoated silt grains on faces of coarse peds and many distinct uncoated silt grains on faces of medium peds; few faint clay films on faces of medium peds and lining pores; trace of pebbles and stones; neutral (pH 6.8); clear smooth boundary. (10 to 15 inches thick)
Bt2--34 to 45 inches; light yellowish brown (10YR 6/4) loam, yellowish brown (10YR 5/4) moist; strong very coarse subangular blocky structure; hard, friable, sticky and plastic; few very fine roots; many very fine and common fine tubular pores; few faint uncoated silt grains on faces of peds; few faint clay films on faces of peds and lining pores; trace of pebbles and stones; neutral (pH 7.0); clear smooth boundary. (10 to 15 inches thick)
BC--45 to 52 inches; light yellowish brown (10YR 6/4) loam, yellowish brown (10YR 5/4) moist; weak very coarse prismatic structure; hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine and few fine tubular pores; common faint uncoated silt grains on faces of peds; trace of pebbles and stones; neutral (pH 7.0); clear smooth boundary. (0 to 15 inches thick)
C--52 to 70 inches; light yellowish brown (10YR 6/4) loam, yellowish brown (10YR 5/4) moist; massive; hard, very friable, slightly sticky and slightly plastic; common very fine and few fine tubular pores; trace of pebbles and stones; neutral (pH 7.0).
TYPE LOCATION: Fremont County, Idaho; about 30 miles north of St.Anthony, Idaho; about 1,100 feet north and 500 feet west of the southeast corner of section 5, T. 12 N., R. 41 E.; Latitude - 44 degrees, 23 minutes, 36 seconds North; Longitude - 111 degrees, 38 minutes, 19 seconds West.
RANGE IN CHARACTERISTICS:
Ochric epipedon thickness - 12 to 24 inches
Depth to argillic horizon - 12 to 24 inches
Depth of solum - 40 to greater than 60 inches
Rock fragments - 0 to 15 percent in the particle-size control section
Clay content in the particle-size control section, weighted average - 18 to 24 percent
Volcanic glass content - 5 to 30 percent in the 0.02 to 2.0 mm size fraction
Ammonium oxalate extractable Al plus 1/2 Fe - 0.1 to 1.0 percent
Phosphate retention - 20 to 50 percent
Mean annual soil temperature - 36 to 40 degrees F.
Mean summer soil temperature - 41 to 45 degrees F. with an O horizon; 46 to 50 degrees F. without an O horizon.
Moisture control section - between 4 and 12 inches; dry throughout the moisture control section for 30 to 45 consecutive days during the four months following the summer solstice.
A horizon - Value: 4 to 6 dry, 2 to 4 moist
Chroma: 2 or 3 dry or moist
Base saturation by ammonium acetate: 30 to 50 percent
Reaction: strongly acid to slightly acid
E horizons - Value: 6 or 7 dry, 4 or 5 moist
Texture: SIL, L or VFSL
Base saturation by ammonium acetate: 50 to 100 percent
Reaction: moderately acid to neutral
Bt horizons - Value 5 or 6 dry, 4 or 5 moist
Chroma 3 or 4 dry or moist
Texture L, SCL or FSL
Base saturation by ammonium acetate: 80 to 100 percent
Reaction slightly acid or neutral
Other: Thickness of uncoated silt grains or silt coats between abutting peds is less than 2 mm.
BC and C horizons - Value: 5 to 7 dry, 4 to 6 moist
Chroma: 3 or 4 dry or moist
Texture: L, FSL or VFSL
Base saturation by ammonium acetate: 80 to 100 percent
Reaction: slightly acid or neutral
COMPETING SERIES: This is the Vitroff (T) (MT) series. Vitroff soils have an ustic moisture regime, have E horizons and have horizons containing lamellae.
GEOGRAPHIC SETTING: Hopburn soils are on plains. The topography is undulating to rolling with slopes ranging from 1 to 12 percent. The soil formed in local alluvium derived dominantly from loess and volcanic ash. Elevations range from 6,300 to 6,800 feet. The mean annual precipitation is 24 to 30 inches. Mean annual temperature is 34 to 38 degrees F. The frost free period is 30 to 60 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Islandpark, Spliten and Vadnais series. Islandpark soils occur on adjacent plains. They average less than 15 percent fine sand or coarser material throughout the particle-size control section and are 40 to 70 inches deep to the top of the argillic horizon. Spliten and Vadnais soils occur intermixed with the Hopburn soils. Spliten soils have mollic epipedons, lack argillic horizons and are 10 to 20 inches deep over hard bedrock. Vadnais soils have mollic epipedons, lack E horizons and are 20 to 40 inches deep over hard bedrock.
DRAINAGE AND PERMEABILITY: Well drained; slow to moderate runoff; moderately slow permeability.
USE AND VEGETATION: Hopburn soils are used for understory grazing, recreation and wildlife habitat. These soils commonly support lodgepole pine/pinegrass and quaking aspen- lodgepole pine/elk sedge community types. The potential native vegetation is a subalpine fir/pinegrass plant association, pinegrass phase.
DISTRIBUTION AND EXTENT: Southeastern Idaho. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Targhee National Forest, Fremont County, Idaho, 1997.
REMARKS: Location coordinates determined by Global Positioning System.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the mineral soil surface to 21 inches (the A, E1 and E2 horizons).
Argillic horizon - The zone from 21 to 45 inches (the Bt1 and Bt2 horizons).
Particle-size control section - The zone from 21 to 41 inches (the Bt1 and part of the Bt2 horizons).
Vitrandic subgroup feature The zone from the mineral soil surface to 45 inches (A, E1, E2, Bt1, Bt2 horizons)
Moisture regime - udic