LOCATION FORBORD ORTentative Series
TAXONOMIC CLASS: Fine-loamy, isotic, frigid Vitrandic Argixerolls
TYPICAL PEDON: Forbord ashy sandy loam forested, on a 15 percent west-facing slope, at 5380 feet elevation. (Colors are for dry soil unless otherwise noted)
A--0 to 3 inches; very dark grayish brown (10YR 3/2) ashy sandy loam, black (10YR 2/1) moist; weak moderate platy structure parting to moderate fine and medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine vesicular and irregular pores; 5 percent gravel; slightly acid (pH 6.2); abrupt smooth boundary. (2 to 4 inches thick)
Bw--3 to 8 inches; very dark grayish brown (10YR 3/2) ashy sandy clay loam, very dark brown (10YR 2/2) moist; weak medium platy structure parting to moderate fine and medium subangular blocky; soft, friable, slightly sticky and slightly plastic; many very fine, fine and medium roots; many very fine and fine tubular pores; 5 percent gravel; slightly acid (pH 6.4); clear smooth boundary. (4 to 6 inches thick)
Bt1--8 to 16 inches; dark brown (10YR 3/3) sandy clay loam, very dark brown (10YR 2/2) moist; weak medium platy structure parting to moderate fine and medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; many very fine, fine, medium and coarse roots; many very fine and fine tubular pores; common faint clay films bridging sand grains; 5 percent gravel; slightly acid (pH 6.4); clear smooth boundary. (7 to 10 inches thick)
Bt2--16 to 30 inches; dark brown (10YR 3/3) stony sandy clay loam, very dark brown (10YR 2/2) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, sticky and plastic; common fine and medium roots; many very fine and fine tubular pores; common faint clay films bridging sand grains; 5 percent gravel, 5 percent cobbles and 10 percent stones; slightly acid (pH 6.4); clear smooth boundary. (12 to 15 inches thick)
Bt3--30 to 60 inches; dark yellowish brown (10YR 3/4) stony sandy clay loam, very dark brown (10YR 2/2) moist; moderate medium subangular blocky structure; slightly hard, friable, sticky and plastic; common fine and medium roots; many fine and medium tubular pores; common distinct clay films on ped faces and lining pores; 5 percent gravel, 5 percent cobbles and 10 percent stones; slightly acid (pH 6.4).
TYPE LOCATION: Harney County, Oregon; southwest of Association Corral on 4540-950 road;
NW1/4, Section 5, T. 20 S., R. 25. E.
Latitude 43 degrees, 52 minutes, 01 seconds N
Longitude 119 degrees, 45 minutes, 17 seconds W
UTM Coordinates: Zone 11; 4,860,568 northing, 278,640 easting; NAD27
RANGE IN CHARACTERISTICS:
Soil temperature: frigid regime
Mean annual soil temperature: 41 to 45 degrees F.
Mean summer soil temperature: 49 to 53 degrees F.
Mean winter soil temperature: 32 to 36 degrees F.
Soil moisture: xeric regime, dry 75 to 90 consecutive days in summer and early fall
Particle-size control section: upper 20 inches of the argillic horizon
clay content (weighted average): 27 to 35 percent
rock fragment content (weighted average): 10 to 35 percent
Diagnostic horizons and features:
vitrandic subgroup material - upper boundary at the mineral surface, 7 to 10 inches thick
Al+1/2Fe - 0.4 to 1.0 percent (ammonium oxalate)
P retention - 25 to 50 percent
0.2 to 2.0 mm fraction - 60 to 80 percent of fine earth
volcanic glass - 30 to 50 percent of 0.2 to 2.0 fraction
water content at 1500 kPa - 10 to 15 percent (dried samples)
mollic epipedon: 20 to 40 inches thick
argillic horizon: upper boundary 7 to 14 inches below mineral soil surface; 40 inches or more thick
lithic contact, depth below mineral soil surface: 60 to 80 inches
A and Bw horizons
color, moist: 10YR 2/1, 2/2, 3/2
color dry: 10YR 3/4, 4/4, 5/4
texture: ASHY-LS, ASHY-SL, ASHY-SCL
rock fragments: 5 to 15 percent
gravel: 5 to 15 percent
reaction : moderately acid to slightly acid, pH: 5.6 to 6.5
Bt horizons
color moist: 10YR 2/2, 3/2, 3/3, 3/4
color dry: 10YR 3//2, 3/3, 4/3, 4/4, 5/3, 5/4
texture: SCL, CL, ST-SCL, CB-SCL
clay content: 27 to 35 percent
rock fragments: 5 to 35 percent
gravel: 5 to 15 percent
cobbles: 0 to 10 percent
stones: 0 to 10 percent
reaction: moderately acid to slightly acid, pH: 5.6 to 6.5
COMPETING SERIES:
Bly: deep and very deep (40 to greater than 60 inches) to a duripan, dry 60 to 90 days in summer
Bolobin: moderately deep (20 to 40 inches); to a lithic contact (basalt); formed in a mixed mantle of volcanic ash and loess over colluvium from basalt; mixed mantle has 15 to 30 percent volcanic glass; more than 15 percent rock fragments in lower part of the argillic horizon; dry 60 to 75 days in summer
Bolony: moderately deep (20 to 40 inches); to a lithic contact (basalt); formed in loess with a minor influence of volcanic ash over colluvium from basalt; volcanic glass in surface layers is 5 to15 percent; more than 15 percent rock fragments in lower part of the argillic horizon; dry 60 to 75 days in summer
Forshey: very deep (lacks a lithic contact within 60 inches); formed in a mixed mantle of volcanic ash and loess over colluvium from granitic rocks; mixed mantle has 15 to 30 percent volcanic glass; buried 2E horizon below mollic epipedon; dry 60 to 75 days in summer
Hess: deep (40 to 60 inches) to a lithic contact (basalt and tuff); mollic epipedon is 10 to 20 inches thick; particle-size control section has 0 to 15 percent rock fragments and 5 to 50 percent pararock fragments; dry 45 to 75 days in summer
Lidos: very deep (lacks a lithic contact within 60 inches); formed in colluvium from basalt with an influence of volcanic ash in upper part of solum, over alluvium from pyroclastic materials; has 5 to 20 percent glass in volcanic ash influenced mantle; buried genetic horizons developed in pyroclastic alluvium at 30 to 60 inches; dry 45 to 75 days in summer
Melhorn: very deep (lacks a lithic contact within 60 inches); formed in a mixed mantle of volcanic ash and loess over colluvium from basalt; mixed mantle has 20 to 30 percent volcanic glass; 45 to 75 dry days in summer
Nibolob: deep (40 to 60 inches) to a lithic contact (basalt); formed in a mixed mantle of volcanic ash and loess over colluvium from basalt; mixed mantle has 15 to 30 percent volcanic glass; dry 60 to 75 days in summer
Raycreek: moderately deep (20 to 40 inches) to a lithic contact (tuff); formed in a mantle of colluvium mixed with volcanic ash over residuum from metasedimentary rock; volcanic glass in surface layers is 10 to 30 percent; dry 60 to 90 days in summer
Salcreek: very deep (lacks a lithic contact within 60 inches); formed in medisedimentary till with a minor influence of volcanic ash in horizons above the till; ash influenced surface horizons have 5 to 20 percent volcanic glass; particle-size control section has more than 50 percent sand; dry 60 to 70 days in summer
Spartabutte: moderately deep (20 to 40 inches) to a lithic contact (granite); formed in loess with a minor influence of volcanic ash over colluvium from granitic rock; volcanic glass in surface layers is 5 to15 percent; mollic epipedon is 10 to 18 inches thick; dry 60 to 75 days in summer
Vangoe: deep (40 to 60 inches) to a lithic contact (basalt); dry 45 to 60 days in summer
GEOGRAPHIC SETTING:
Landform: rolling hills and mountain slopes
Landform segment: lower backslopes and footslopes, transition zone between forested hills and shrub steppes
Aspect: all
Slope gradient: 5 to 40 percent
Parent material: mixed volcanic ash and loess over colluvium and slope alluvium
Lithology: basalt, rhyolite, pyroclastic tuff, Mesozoic marine sediments
Elevation: 4000 to 6000 feet
Climate: cold, wet winters and hot, dry summers
Mean annual precipitation: 14 to 18 inches
Mean annual temperature: 39 to 43 degrees F.
Frost-free season: 75 to 90 days
GEOGRAPHICALLY ASSOCIATED SOILS:
Wileyflat - on upper and mid-backslope positions; moderately deep
Sintuf - on shoulder and plateau top positions, shallow
Ateron - on plateau tops and rolling sideslopes; shallow
Observation - on rolling sideslope and upland swale positions; moderately deep
Tweener - on plateau top positions on scablands; very shallow
Canest - on plateau top positions on extremely bouldery scablands; very shallow
Cleavage - on plateau top positions in mounds on scabland associations; moderately deep
DRAINAGE AND PERMEABILITY:
Drainage: well drained
Permeability: moderate above the argillic horizon, and moderately slow in the argillic
USE AND VEGETATION:
Use: timber production, livestock grazing, wildlife habitat, and watershed
Potential natural vegetation: ponderosa pine, mountain big sage, whorteleaf snowberry, wax currant, green rabbitbrush, chokecherry, mountain mahogany, rose, wheeler bluegrass and Idaho fescue. Plant Association: CPS5-25. PIPO/SYOR (ponderosa pine/mountain snowberry. Plant Association Group: dry pine
DISTRIBUTION AND EXTENT:
Distribution: MLRA: E43c Central Oregon, southwestern Blue Mountains
Extent: small
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES PROPOSED: Ochoco National Forest, Oregon, 2008
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Vitrandic subgroup feature; the zone from 0 to 8 inches (A, Bw horizons)
mollic epipedon (pachic) the zone from 0 to 30 inches (A, Bw, Bt1, Bt2 horizons)
argillic horizon; the zone from 8 to 60 inches (Bt1, Bt2, Bt3 horizons)