LOCATION POTATOHILL              OR

Tentative Series
IRD. DCR/MPR
02/2025

POTATOHILL SERIES

Landscape--High Cascade volcanic fields
Landform--concave positions on lava flows, kipukas
Slope--2 to 15 percent
Parent material-- volcanic ash and residuum weathered from vesicular basalt
Mean annual precipitation--about 2000 mm
Mean annual air temperature--about 6.5 degrees C
Depth class--very deep
Drainage class--well drained
Soil moisture regime--udic
Soil temperature regime--frigid
Soil moisture subclass--typic

TAXONOMIC CLASS: Medial, amorphic, frigid Humic Udivitrands

TYPICAL PEDON: Potatohill medial fine sandy loam on a 2-percent, forested slope at an elevation of 866 m

Oi--0 to 5 cm; slightly decomposed plant material; clear wavy boundary

A1--5 to 28 cm; medial fine sandy loam, brown (10YR 4/3) dry, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; common very fine through coarse roots; common very fine dendritic tubular pores; 8 percent gravel; moderately acid (pH 5.7); clear wavy boundary

A2--28 to 65 cm; medial fine sandy loam, brown (10YR 5/3) dry, dark brown (10YR 3/3) moist; weak coarse subangular blocky structure; slightly hard, very friable, nonsticky, nonplastic; common very fine and medium and few fine and coarse roots; common very fine and few fine dendritic tubular pores; 5 percent gravel; moderately acid (pH 5.9); clear wavy boundary

Bw1--65 to 87 cm; medial loam, brown (10YR 5/3) dry, dark yellowish brown (10YR 3/4) moist; weak coarse subangular blocky structure; slightly hard, friable, nonsticky, nonplastic; few very fine and medium roots; common very fine and few fine dendritic tubular pores; 5 percent gravel and 1 percent moderately coherent fine pumice paragravel; moderately acid (pH 6.0); clear smooth boundary

Bw2--87 to 112 cm; medial loam, brown (10YR 5/3) dry, brown (10YR 4/3) moist; weak coarse subangular blocky structure; moderately hard, friable, nonsticky, nonplastic; few very fine and medium roots; common very fine and few fine dendritic tubular pores; 8 percent gravel and 1 percent moderately coherent fine pumice paragravel; slightly acid (pH 6.1); clear smooth boundary

Bw3--112 to 150 cm; gravelly medial loam, brown (10YR 5/3) dry, brown (10YR 4/3) moist; weak coarse subangular blocky structure; moderately hard, friable, nonsticky, nonplastic; few very fine roots; common very fine and few fine dendritic tubular pores; 15 percent gravel, 1 percent moderately coherent fine pumice paragravel, and 3 percent cobbles; slightly acid (pH 6.1)

TYPE LOCATION: Linn County, Oregon, 3.5 km east of Trail Bridge Reservoir; 230 m south and 630 m east of the northwest corner of section 17, T. 15 S., R. 7 E.; latitude 44.27096, longitude -122.00201, datum WGS 84 (coordinates determined with a GPS)

RANGE IN CHARACTERISTICS:
Dry days--less than 45 consecutive days following summer solstice
Mean annual soil temperature--6 to 8 degrees C
Thickness of umbric epipedon--25 to 75 cm
Depth to base of Bw2 horizon--greater than 100 cm below the mineral soil surface
Thickness of andic soil properties--greater than 150 cm below the mineral surface

Particle-size control section (weighted average)
*Clay content--less than 18 percent
*Total fragment content--less than 15 percent
*Phosphate retention--greater than 85 percent
*Ammonium oxalate extractable Al + 1/2 Fe--2.0 to 4.0 percent
*Particles 0.02- to 2.0-mm--greater than 30 percent of the fine-earth fraction
*Fine-earth fraction--contains less than 50 percent medium through very coarse sand
*Volcanic glass content in 0.02 to 2.0 mm fraction--60 to 90 percent

O horizons
*Composition--slightly to moderately decomposed plant material
*Combined thickness--0 to 8 cm

A horizons
*Value--2 or 3 moist, 4 or 5 dry
*Chroma--2 or 3 moist and dry
*Fine-earth texture--medial fine sandy loam, medial sandy loam
*Clay content--2 to 10 percent
*Sand content--50 to 70 percent
*Gravel content--0 to 15 percent
*Pumice paragravel content--0 to 5 percent
*Organic carbon content--3 to 6 percent
*1500 kPa water (air-dried samples)--12 to 15 percent
*Thickness--36 to 75 cm

Bw1 and Bw2 horizons
*Value--4 or 5 moist, 5 or 6 dry
*Chroma--3 or 4 moist or dry
*Fine-earth texture--medial fine sandy loam, medial loam
*Clay content--5 to 18 percent
*Sand content--40 to 60 percent
*Gravel content--0 to 15 percent
*Pumice paragravel content--0 to 5 percent
*1500 kPa water (air-dried samples)--greater than 15 percent
*Organic carbon content--0.5 to 2 percent
*Reaction--pH 5.6 to 6.5
*Thickness--25 to greater than 125 cm

Bw3 horizon (when present)
*Value--4 or 5 moist, 5 or 6 dry
*Chroma--3 or 4 moist or dry
*Fine-earth texture--medial fine sandy loam, medial loam
*Clay content--5 to 18 percent
*Sand content--40 to 60 percent
*Total fragment content--15 to 35 percent
*Gravel content--5 to 20 percent
*Cobble content--0 to 15 percent
*Stone content--0 to 15 percent
*Pumice paragravel content--0 to 5 percent
*1500 kPa water (air-dried samples)--greater than 15 percent
*Organic carbon content--0.5 to 2.0 percent
*Reaction--pH 5.6 to 6.5

COMPETING SERIES:
Pioneergulch--particle-size control section averages 5 to 25 percent pumice paragravel; very high saturated hydraulic conductivity below the solum

GEOGRAPHIC SETTING:
Elevation--800 to 1175 m
Climate--cool, wet winters; warm, dry summers
Mean annual precipitation--1800 to 2200 mm
Mean annual air temperature--5 to 7 degrees C
Frost-free period--75 to 135 days

GEOGRAPHICALLY ASSOCIATED SOILS:
Limberlost--averages greater than 35 percent rock fragments in the particle-size control section; located on convex positions on lava flows
Proxy--densic contact between 100 and 150 cm; located on glaciated mountains and lateral moraines

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--well drained
Saturation in normal years--none within profile
Flooding--none
Ponding--none
Saturated hydraulic conductivity (Ksat)--high

USE AND VEGETATION:
Use--watershed, recreation, wildlife habitat, timber production
Potential natural vegetation--Douglas-fir, western white pine, western hemlock, grand fir, vine maple, beaked hazelnut; Cascade barberry, snowberry, and sweet after death; commonly supports a grand fir/dwarf Oregon grape (CWS522) plant association (Field Guide to the Forested Plant Associations of the Westside Central Cascades of Northwest Oregon)

DISTRIBUTION AND EXTENT: High Cascade Mountains, Oregon; MLRA 3; small extent

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana

SERIES PROPOSED: Willamette National Forest, Linn County, Oregon; named for ridge near Santiam Pass

REMARKS:
Diagnostic horizons and features recognized in this pedon
*Particle-size control section--zone from 5 to 105 cm
*Umbric epipedon--zone from 5 to 65 cm
*Cambic horizon--zone from 65 to 150 cm
*Andic soil properties--zone from 5 to 150 cm
*Volcanic glass--zone from 5 to 150 cm

11/2022--meets criteria #3 for andic soil properties, in the 13th edition of Keys to Soil Taxonomy

ADDITIONAL DATA: Type location user pedon ID--2022OR043841

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National Cooperative Soil Survey
U.S.A.