LOCATION LITTLEDOME OR
Tentative Series
IRD. DCR/MPR
02/2025
LITTLEDOME SERIES
Landscape--southwestern Middle Cascade mountains
Landform--complex landslides
Slope--0 to 15 percent
Parent material--pumice and volcanic ash over residuum and colluvium derived from tuff
Mean annual precipitation--about 1600 mm
Mean annual air temperature--about 6 degrees C
Depth class--very deep
Drainage class--moderately well drained
Soil moisture regime--udic
Soil temperature regime--frigid
Soil moisture subclass--oxyaquic
TAXONOMIC CLASS: Fine-loamy, isotic, frigid Andic Oxyaquic Dystrudepts
TYPICAL PEDON: Littledome very paragravelly ashy coarse sandy loam, on a forested complex landslide with a slope of 4 percent and an elevation of 1034 m
Oi--0 to 4 cm; slightly decomposed plant material, clear wavy boundary
A --4 to 32 cm; very paragravelly ashy coarse sandy loam, pale brown (10YR 6/3) dry, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; soft, very friable, nonsticky, nonplastic; many very fine and common fine through coarse roots; many very fine irregular pores; 10 percent gravel and 35 percent pumice paragravel; moderately acid (pH 5.8); clear smooth boundary
2Bw1--32 to 55 cm; gravelly silt loam, pale brown (10YR 6/3) dry, brown (10YR 4/3) moist; weak medium subangular blocky structure; moderately hard, friable, slightly sticky, moderately plastic; common very fine to medium and few coarse roots; common very fine dendritic tubular pores; 15 percent gravel and 5 percent cobbles; moderately acid (pH 5.6); clear smooth boundary
2Bw2--55 to 75 cm; cobbly silt loam, pale brown (10YR 6/3) dry, brown (10YR 4/3) moist; weak medium subangular blocky structure; hard, friable, moderately sticky, moderately plastic; common very fine and few medium roots; common very fine dendritic tubular pores; 15 percent gravel and 12 percent cobbles; moderately acid (pH 5.6); clear smooth boundary
2Bw3--75 to 92 cm; gravelly silty clay loam, light yellowish brown (10YR 6/4) dry, dark yellowish brown (10YR 4/4) moist; weak coarse subangular blocky structure; very hard, friable, moderately sticky, very plastic; few medium and very fine roots; common very fine dendritic tubular pores; 12 percent gravel and 5 percent cobbles; strongly acid (pH 5.4); clear smooth boundary
2Bw4--92 to 150 cm; gravelly silty clay loam, light yellowish brown (10YR 6/4) dry, dark yellowish brown (10YR 4/4) moist; weak coarse subangular blocky structure; very hard, friable, moderately sticky, very plastic; few very fine roots; common very fine dendritic tubular pores; 2 percent strong brown (7.5YR 4/6) iron-manganese masses in matrix; 12 percent gravel, 5 percent cobbles, and 5 percent tuff paragravel; strongly acid (pH 5.4)
TYPE LOCATION: Douglas County, Oregon, about 21 km southwest of Diamond Peak, in Willamette National Forest; 740 m south and 350 m west of the northeast corner of section 6, T. 25 S., R. 4 E., Willamette Meridian; latitude 43.43497, longitude -122.37440, datum WGS 84 (coordinates determined with a GPS)
RANGE IN CHARACTERISTICS:
Mean annual soil temperature--6 to 8 degrees C
Depth to lithologic discontinuity--18 to 36 cm below the mineral soil surface
Depth to redox concentrations--60 to 100 cm below the mineral soil surface
Thickness of andic soil properties--18 to 36 cm
Properties of layers meeting andic subgroup criteria
*1/3-bar bulk density--0.6 to 0.9 g/cm3
*Phosphate retention--50 to 85 percent
*Ammonium oxalate Al plus 1/2 Fe--1.0 to 2.0 percent
*1500 kPa water (air-dried samples)--less than 12 percent
*1500 kPa water (undried)--less than 30 percent
*Volcanic glass content in 0.02 to 2.0 mm fraction--60 to 90 percent
Particle-size control section (weighted average)
*Clay content--18 to 35 percent
*Total rock fragments--5 to 35 percent
O horizon
*Composition--slightly to moderately decomposed plant material
*Thickness--0 to 8 cm
A horizon
*Value-3 or 4 moist, 5 or 6 dry
*Chroma--2 or 3 moist and dry
*Clay content--5 to 12 percent
*Sand content--55 to 75 percent
*Total fragment content--15 to 60 percent
*Pumice paragravel content--15 to 60 percent
*Gravel content--0 to 15 percent
*Cobble content--0 to 5 percent
*Reaction--pH 5.1 to 6.0
*Thickness--18 to 36 cm
2Bw horizons
*Value--4 or 5 moist, 5 or 6 dry
*Chroma--2 to 4 moist or dry
*Fine-earth texture--silt loam, silty clay loam, clay loam
*Clay content--18 to 35 percent
*Sand content--15 to 35 percent
*Total fragment content--5 to 35 percent
*Gravel content--5 to 35 percent
*Tuff paragravel content--0 to 15 percent
*Cobble content--0 to 15 percent
*Reaction--pH 5.1 to 6.0
COMPETING SERIES: None
GEOGRAPHIC SETTING:
Elevation--910 to 1225 m
Climate--warm, dry summers; cool, wet winters
Mean annual precipitation--1400 to 1800 mm
Mean annual air temperature--5 to 7 degrees C
Frost-free period--90 to 150 days
GEOGRAPHICALLY ASSOCIATED SOILS:
Illahee--umbric epipedon; located on mountain slopes
Staleycreek--greater than 150 cm to redox concentrations, averages 18 to 27 percent clay in the particle-size control section; located on colluvial aprons, glacial-valley walls, and mountain slopes
Pioneergulch--umbric epipedon, averages less than 10 percent clay in the particle-size control section; located on moraines and colluvial aprons
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--moderately well drained
Flooding--none
Ponding--none
Saturated hydraulic conductivity (Ksat)--moderately high
USE AND VEGETATION:
Use--timber production, wildlife habitat, recreation
Potential natural vegetation--Douglas-fir, sugar pine, western hemlock, giant chinquapin, Pacific rhododendron, Cascade barberry; commonly supports a western hemlock/rhododendron-dwarf Oregon grape (CHS356) plant association (see Field Guide to the Forested Plant Associations of the Westside Central Cascades of Northwest Oregon)
DISTRIBUTION AND EXTENT: Southwestern Cascade Mountains, Oregon; MLRA 3; small extent
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Willamette National Forest, Douglas County, Oregon; 2022; name from peak near the type location
REMARKS:
Diagnostic horizons and other features in this pedon
*Particle-size control section--zone from 29 to 104 cm
*Ochric epipedon
*Cambic horizon--32 to 150 cm
*Andic soil properties--zone from 4 to 32 cm
*Volcanic glass--zone from 4 to 32 cm
*Depth to lithologic discontinuity--32 cm
*Redox concentrations--92 to 150 cm
*Aquic conditions--92 to 150 cm
*Endosaturation--92 to 150 cm
*Typical pedon ID--2020OR019864
National Cooperative Soil Survey
U.S.A.