LOCATION STITHUM OR

Tentative Series
IRD. JLW/RJO/DAL
02/2019

STITHUM SERIES

The Stithum series consists of very deep, well-drained soils on mountain valley, eroded alluvial terraces. Stithum soils formed in colluvium mixed with a small amount of volcanic ash, overlying alluvium from mixed lithologies. Slopes are 0 to 30 percent. Mean annual precipitation is about 30 inches and mean annual temperature about 42 degrees F.

TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Vertic Haploxeralfs

TYPICAL PEDON: Stithum gravelly ashy loam - forested, on a 5 percent northwestfacing slope at an elevation of 3,980 feet.

Oi--0 to 1 inch; slightly decomposed grasses, needles and twigs

A1--1 to 4 inches; dark reddish brown (5YR 3/2) gravelly ashy loam, reddish brown (5YR 5/3) dry; weak fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, common fine, and few medium roots throughout; common very fine irregular pores; 20 percent gravel; moderately acid (pH 6.0); clear wavy boundary. (3 to 8 inches thick)

A2--4 to 9 inches; reddish brown (5YR 4/3) gravelly ashy loam, reddish brown (5YR 5/3) dry; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine, and few medium roots throughout; common very fine irregular and few very fine tubular pores; 20 percent gravel; slightly acid (pH 6.2); clear wavy boundary. (4 to 15 inches thick)

E--9 to 19 inches; reddish brown (5YR 4/3) gravelly clay loam, brown (7.5YR 5/4) dry; weak medium subangular blocky structure parting to weak fine subangular blocky; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine, and few medium and coarse roots throughout; common very fine irregular and few very fine and fine tubular pores; 15 percent gravel and 5 percent cobbles; slightly acid (pH 6.2); clear irregular boundary. (10 to 21 inches thick)

2Bt--19 to 30 inches; yellowish brown (10YR 5/4) extremely gravelly clay loam, brown (7.5YR 5/4) dry; moderate medium and fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common thin clay films on ped faces; few fine, very fine, and medium roots throughout; few fine and very fine tubular pores; 60 percent gravel and 10 percent cobbles; slightly acid (pH 6.2); gradual irregular boundary. (8 to 35 inches thick)

2BC--30 to 60 inches; dark yellowish brown (10YR 4/4) extremely gravelly sandy clay, brown (7.5YR 5/4) dry; weak fine subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; few very fine roots throughout; common very fine irregular and few very fine tubular pores; 60 percent gravel and 10 percent cobbles; slightly acid (pH 6.2).

TYPE LOCATION: Grant County, Oregon,
Section 5 (SW 1/4, SW 1/4, SW 1/4), T. 11 S., R. 34 E.
Latitude: 44 degrees, 38 minutes, 10.4 seconds N
Longitude: 118 degrees, 39 minutes 05.5 seconds W
UTM coordinates: zone 11; north 4943650.0 meters, east 369010.0 meters; NAD27
USGS Quadrangle: Boulder Butte

RANGE IN CHARACTERISTICS:
Soil Temperature: frigid regime
Mean Annual Soil Temperature: 43 to 46 degrees F
Mean Summer Soil Temperature: 51 to 54 degrees F
Mean Winter Soil Temperature: 34 to 38 degrees F
Soil Moisture: xeric regime, dry 60 to 75 consecutive days in summer

Particle-size Control Section: upper 20 inches of argillic horizon
clay content, average: 35 to 40 percent
rock fragment content, average: 50 to 75 percent

Diagnostic Horizons and Features:
vitrandic subgroup properties: upper boundary at the mineral soil surface; 9 to 19 inches thick
Al+1/2Fe (ammonium oxalate): 0.2 to 0.9 percent
glass content in the 0.02-2.0mm fraction: 5 to 15 percent
argillic horizon: 11 to 40 inches
linear extensibility: 4.8 to 6.0 cm in upper 100 cm of mineral soil
rock fragment shape: rounded or subrounded in subsoil and substratum

A1 horizon:
color, moist: 5YR 3/2, 3/3, 3/4; 7.5YR 3/4; 10YR 3/3
color, dry: 5YR 5/3; 7.5YR 6/3; 10YR 5/3
texture: ASHY-SIL, GR-ASHY-L
clay content: 7 to 22 percent
rock fragment content: total: 5 to 25 percent
gravel: 0 to 20 percent
cobbles: 0 to 10 percent
reaction: moderately acid or slightly acid; pH: 5.6 to 6.5
base saturation (sum of cations): 50 to 75 percent

A2 horizon; may include AB and/or Bw in some pedons:
color, moist: 5YR 4/2, 4/3; 7.5YR 4/4; 10YR 4/6
color, dry: 5YR 5/3, 6/3; 7.5YR 5/4, 6/3
texture: GR-ASHY-L, CBV-ASHY-L, GR-ASHY-SIL, CBV-ASHY-SIL
clay content: 10 to 26 percent
rock fragment content: 15 to 45 percent
gravel: 10 to 20 percent
cobbles: 0 to 20 percent
stones: 0 to 5 percent
reaction: moderately acid or slightly acid; pH: 5.6 to 6.5.
base saturation (sum of cations): 50 to 75 percent

E horizon; may include 2EBb, 2Eb horizons in some pedons:
color, moist: 5YR 4/3; 7.5YR 3/4, 4/3, 4/4; 10YR 5/6
color, dry: 5YR 5/3; 7.5YR 5/4, 6/3, 6/4; 10YR 7/6
texture: GRV-CL, GR-CL, CBV-L, STV-L
clay content: 19 to 34 percent
rock fragment content: 20 to 60 percent
gravel: 10 to 40 percent
cobbles: 5 to 25 percent
stones: 0 to 15 percent
reaction: moderately acid or slightly acid; pH: 5.6 to 6.5
base saturation (sum of cations): 45 to 70 percent

2Bt horizon:
color, moist: 7.5YR 3/4, 4/4, 5/6; 10YR 5/4
color, dry: 7.5YR 5/4, 6/6; 10YR 6/3
texture: CBX-C, GRV-C, STX-CL, CBV-C, GRX-CL
clay content: 35 to 42 percent
rock fragment content: 50 to 75 percent
gravel: 20 to 60 percent
cobbles: 10 to 30 percent
stones: 0 to 25 percent
reaction: moderately acid to neutral; pH: 5.6 to 7.3
base saturation (sum of cations): 60 to 75 percent

2BC horizon:
color, moist: 7.5YR 4/4, 5/6; 10YR 4/4
color, dry: 7.5YR 5/4, 6/6
texture: CBX-C, CBX-CL, GRX-SC
clay content: 34 to 41 percent
rock fragment content: 65 to 95 percent
gravel: 30 to 70 percent
cobbles: 10 to 25 percent
stones: 0 to 10 percent
reaction: slightly acid to slightly alkaline; pH: 6.1 to 7.8
base saturation (sum of cations): 70 to 100 percent

COMPETING SERIES:
Cotay: moderately deep (20 to 40 inches) to a lithic contact (metavolcanic, serpentinitic); cambic (Bw) is silt loam with 6 to 22 percent clay; have buried eluvial (2Eb) horizons; rock fragments are angular in shape; dry 45 to 60 consecutive days in summer
Cougarrock: moderately deep (20 to 40 inches) to a lithic contact (soft tuffs or basalt); cambic (Bw) is silt loam with 10 to 22 percent clay; have buried eluvial (2Eb) horizons; have paralithic material (soft rock) 3 to 10 inches thick above lithic contact; rock fragments are subangular in shape; dry 45 to 60 consecutive days in summer
Dunstan: deep (40 to 60 inches) to a lithic contact (andesitic tuff breccia); cambic (Bw) is silt loam with 12 to 22 percent clay; have buried eluvial (2Eb) horizons; rock fragments are subangular in shape; dry 45 to 60 consecutive days in summer
Tamarackcanyon: moderately deep (20 to 40 inches) to a lithic contact (basalt); cambic (Bw) is clay loam or silty clay loam with 25 to 35 percent clay; do not have eluvial (2Eb) horizons; rock fragments are angular or subangular in shape; dry 45 to 60 consecutive days in summer

GEOGRAPHIC SETTING:
Landform: eroding stream terraces in mountain valleys
Slope gradient: 0 to 30 percent
Parent material: minor amount of volcanic ash mixed with eolium and colluvium over alluvium
Lithology: alluvium of mixed non-calcareous rocks
Elevation: 3,800 to 4,600 feet
Climate: cold, wet winters; warm, dry summers
Mean annual precipitation: 24 to 35 inches
Mean annual air temperature: 41 to 44 degrees F.
Frost-free period: 45 to 100 days

GEOGRAPHICALLY ASSOCIATED SOILS:
Squatterflat: on planar to convex terrace surfaces and upper backslopes of mountain valley terraces; very deep; mollic epipedon with small amount of volcanic ash and argillic horizon developed in residuum from andesitic tuff breccia; under Douglas-fir, ponderosa pine, western larch, common snowberry, birchleaf spiraea, wormleaf stonecrop, white hawkweed, elk sedge and pinegrass.

DRAINAGE AND PERMEABILITY:
Drainage: well drained
Permeability: moderate over slow

USE AND VEGETATION:
Use: timber production, livestock grazing, recreation, wildlife habitat, watershed
Native vegetation: grand fir, Douglas-fir, western larch, ponderosa pine, birchleaf spiraea, common snowberry, grouse huckleberry, bigleaf sandwort, silky lupine, raceme pussytoes, white hawkweed, Virginia strawberry, common yarrow, Cusick's sierra peavine, pinegrass, elk sedge, and western fescue.
Plant Association: PSME/CARU (Douglas-fir/pinegrass); may include: ABGR/CARU (grand fir/pinegrass) or PIPO/SYAL (ponderosa pine/common snowberry)

DISTRIBUTION AND EXTENT:
Distribution: MLRA: 43c, Blue Mountains in Oregon; South Central Blue Mountains in Middle Fork and North Fork of John Day River drainage.
Extent: Moderate

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES PROPOSED: Malheur National Forest, Oregon; 2008. The name is from the Stithum Mine on the Boulder Butte quadrangle.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
ochric epipedon: 1 to 4 inches; A1 horizon
vitrandic subgroup properties (ash influenced layer): 1 to 9 inches; A1, A2 horizons
eluvial horizon: 9 to 19 inches; E horizon
argillic horizon, buried: 19 to 30 inches; Bt horizon
particle-size control section: 19 to 30 inches; Bt horizon

National Cooperative Soil Survey
U.S.A.