LOCATION SOOSAP OR
Established Series
AJG/GLG/RWL
02/2025
SOOSAP SERIES
Landscape--western Cascade mountains
Landform--mountaintops
Slope--2 to 30 percent
Parent material--colluvium and residuum weathered from tuff mixed with volcanic ash
Mean annual precipitation--about 2500 mm
Mean annual air temperature--about 5 degrees C
Depth class--moderately deep to paralithic bedrock
Drainage class--well drained
Soil moisture regime--udic
Soil temperature regime--cryic
Soil moisture subclass--typic
TAXONOMIC CLASS: Medial, amorphic Typic Haplocryands
TYPICAL PEDON: Soosap medial loam, forested
Oi--0 to 3 cm; slightly decomposed needles, leaves, and twigs
A1--3 to 18 cm; gravelly medial loam, dark grayish brown (10YR 4/2) dry, very dark brown (10YR 2/2) moist; moderate fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; slightly smeary; many very fine, fine, and medium roots; many irregular pores; 15 percent gravel; very strongly acid (pH 5.0); clear smooth boundary
A2--18 to 36 cm; medial loam, dark grayish brown (10YR 4/2) dry, very dark brown (10YR 2/2) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; slightly smeary; many very fine, fine, and medium roots; many irregular pores; 10 percent gravel; strongly acid (pH 5.4); clear smooth boundary
Bw1--36 to 56 cm; medial loam, brown (10YR 4/3) dry, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; slightly smeary; many very fine and fine roots; many very fine tubular pores; 10 percent gravel; strongly acid (pH 5.4); clear smooth boundary
Bw2--56 to 91 cm; medial loam, brown (10YR 4/3) dry, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; slightly smeary; common very fine and fine roots; many very fine tubular pores; 10 percent gravel; strongly acid (pH 5.2); clear smooth boundary
Cr--91 to 114 cm; very weakly coherent tuff
R--114 cm; tuff
TYPE LOCATION: Clackamas County, Oregon, about 4 km west of Cougar Lake; in the NE1/4 of the SE1/4 of the NW1/4, section 15, T. 6 S., R. 4 E., Willamette Meridian; Soosap Peak USGS 7.5-minute quadrangle; latitude 45.0496, -122.3054, datum WGS 84 (coordinates estimated from PLSS)
RANGE IN CHARACTERISTICS:
Dry days--fewer than 45 consecutive days following summer solstice
Mean annual soil temperature--5 to 8 degrees C
Depth to paralithic contact--50 to 100 cm
Hue--10YR or 7.5YR
Reaction--pH 4.5 to 6.0
Estimated properties of layers with andic soil properties
*Ammonium oxalate extractable Al plus 1/2 Fe--2 to 4 percent
*Particles 0.02- to 2.0 -mm diameter--greater than 30 percent of the fine-earth fraction
*Volcanic glass content in 0.02- to 2.0-mm fraction--5 to 30 percent
*Phosphate retention--85 to 100 percent
*15-bar water retention--30 to 70 percent (undried samples), 15 to 30 percent (dried samples)
*1/3-bar bulk density--0.6 to 1.1 g/cm3
Particle size control section (weighted average)
*Clay content--10 to 18 percent
*Total rock fragments--5 to 35 percent
O horizons
*Composition--slightly to moderately decomposed plant material
*Thickness--0 to 10 cm
A horizons
*Value--2 to 3 moist, 3 to 5 dry
*Chroma--1 to 3 moist or dry
*Total fragment content--5 to 35 percent
*Gravel content--5 to 30 percent
*Cobble content--0 to 5 percent
*Combined thickness--18 to 64 cm
Bw horizons
*Value--3 or 4 moist, 4 to 6 dry
*Chroma--2 to 4 moist or dry
*Fine-earth texture--medial loam, medial silt loam
*Total fragment content--5 to 35 percent
*Gravel content--0 to 25 percent
*Cobble content--0 to 10 percent
*Combined thickness--33 to 64 cm
Cr horizon
*Value--3 or 4 moist, 4 to 6 dry
*Chroma--2 to 4 moist or dry
COMPETING SERIES:
Cruiser--greater than 100 cm to bedrock; averages 20 to 30 percent clay in the particle-size control section
Keel--averages 18 to 32 percent clay; average more than 18 percent clay in the particle-size control section
Oneonta--greater than 150 cm to bedrock
Longbow--greater than 150 cm to bedrock
Molawa--greater than 150 cm to bedrock
Soapgrass--greater than 150 cm to bedrock
Separation--50 to 100 cm to a densic contact
GEOGRAPHIC SETTING:
Elevation--850 to 1525 m
Climate--timber production, water supply, wildlife habitat, recreation
Mean annual precipitation--1700 to 3600 mm
Mean annual air temperature--4 to 7 degrees C
Frost-free period--30 to 105 days
GEOGRAPHICALLY ASSOCIATED SOILS:
Highcamp--100 to 150 cm to bedrock, ochric epipedon; located on mountain slopes
Kinzel--greater than 150 cm to bedrock and averages greater than 6 percent organic carbon in the upper 30 cm of an umbric epipedon; located on colluvial aprons, cirque floors, mountain slopes, and broad ridgetops
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--well drained
Saturation in normal years--none
Flooding--none
Ponding--none
Saturated hydraulic conductivity (Ksat)--moderately high or high
USE AND VEGETATION:
Use--timber production, water supply, wildlife habitat, recreation
Potential natural vegetation--Douglas fir, noble fir, mountain hemlock, vine maple, Cascade barberry, salal, Pacific rhododendron, red huckleberry, thinleaf huckleberry, and common beargrass
DISTRIBUTION AND EXTENT: Western slope of the Cascade Mountains in northwestern Oregon; MLRA 3; moderate extent
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Clackamas County, Oregon; 1982
REMARKS:
Diagnostic horizons and features recognized in this pedon
*Particle-size control section--zone from 3 to 91 cm
*Umbric epipedon--zone from 3 to 91 cm (upper 30 cm averages less than 6 percent organic carbon)
*Andic soil properties--zone from 3 to 91 cm
*Volcanic glass--zone from 3 to 91 cm
*Depth to paralithic contact--91 cm
*Paralithic materials--91 to 114 cm
*Depth to lithic contact--114 cm
09/2023-- all mineral horizons meet criteria #3 for andic soil properties in the 13th edition of Keys to Soil Taxonomy. All pedons have third-bar bulk density low enough to also meet criteria #2 (no ash required) throughout the umbric epipedon, and some pedons meet criteria #2 throughout the profile.
09/2004--this draft represents a change in classification from Medial Andic Cryumbrepts to Medial, amorphic Typic Haplocryands based on the Andisol Order
National Cooperative Soil Survey
U.S.A.