LOCATION ILLAHEE OR
Established Series
Rev. RGC/TDT/DCR
02/2025
ILLAHEE SERIES
Landscape--western Cascade mountains
Landform--mountain slopes, mountains
Slope--2 to 90 percent
Parent material--colluvium derived from welded tuff and basalt
Mean annual precipitation--about 1800 mm
Mean annual air temperature--about 6 degrees C
Depth class--very deep
Drainage class--well drained
Soil moisture regime--udic
Soil temperature regime--frigid
Soil moisture subclass--typic
TAXONOMIC CLASS: Loamy-skeletal, isotic, frigid Andic Humudepts
TYPICAL PEDON: Illahee very gravelly loam, on a northwest slope of 35 percent under coniferous forest at an elevation of 1294 m
Oi--0 to 3 cm; slightly decomposed fir needles, twigs, and fern fronds
A1--3 to 28 cm; very gravelly loam, dark grayish brown (10YR 4/2) dry, black (10YR 2/1) moist; moderate fine granular structure; slightly hard, friable, nonsticky and nonplastic; many very fine, fine, and medium, and common coarse roots; common very fine irregular pores; 35 percent gravel; strongly acid; clear wavy boundary
A2--28 to 41 cm; very gravelly loam, brown (10YR 5/3) dry, very dark brown (10YR 2/2) moist; moderate fine and medium granular structure; slightly hard, friable, nonsticky and nonplastic; many very fine, fine and medium, and common coarse roots; common very fine irregular pores; 40 percent gravel; very strongly acid; clear wavy boundary
Bw1--41 to 99 cm; very gravelly loam, pale brown (10YR 6/3) dry, very dark grayish brown (10YR 3/2) moist; weak very fine and fine subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common very fine, fine, medium and coarse roots; common fine irregular pores; 45 percent gravel and 5 percent cobbles; strongly acid; clear wavy boundary
Bw2--99 to 122 cm; very gravelly loam, light yellowish brown (10YR 6/4) dry, dark brown (10YR 3/3) moist; weak very fine and fine subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; common very fine, fine, and medium roots; common fine irregular pores; 40 percent gravel and 10 percent cobbles; strongly acid; clear wavy boundary
BC--122 to 150 cm; very cobbly loam, very pale brown (10YR 7/4) dry, dark yellowish brown (10YR 3/4) moist; weak very fine and fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine, and medium roots; common fine irregular pores; 30 percent gravel and 25 percent cobbles; very strongly acid
TYPE LOCATION: Douglas County, Oregon; about 4 km northwest of Burnt Mountain; 352 m east and 288 m south of the northwest corner of section 35, T. 25 S., R. 2 W., Willamette Meridian; latitude 43.35538, longitude -122.90902, datum WGS 84 (coordinates estimated from PLSS)
RANGE IN CHARACTERISTICS:
Mean annual soil temperature--5 to 8 degrees C
Thickness of umbric epipedon--25 to 50 cm
Thickness of materials meeting andic subgroup criteria--18 to 50 cm
Solum thickness--greater than 100 cm
Hue--10YR, 7.5YR
Rock fragment lithology--basalt, welded tuff
Reaction--pH 4.5 to 6.0
Estimated properties of layers meeting andic subgroup criteria
*1/3-bar bulk density--0.7 to 1.0 g/cm3
*Phosphate retention--50 to 100 percent
*Ammonium oxalate extractable Al plus 1/2 Fe--1.0 to 2.0 percent
*Particles 0.02- to 2.0-mm--greater than 30 percent of the fine-earth fraction
*Volcanic glass content in the 0.02 to 2.0 mm fraction--less than 5 percent (weighted average)
*Volcanic glass content in the coarse silt fraction--5 to 10 percent
Particle-size control section (weighted average)
*Clay content--18 to 25 percent
*Total fragment content--35 to 70 percent
Oi horizon
*Thickness--0 to 8 cm
A horizons
*Value--2 to 3 moist, 4 or 5 dry
*Chroma--1 or 2 moist, 2 or 3 dry
*Clay content--10 to 25 percent
*Total fragment content--35 to 60 percent
*Gravel content--35 to 60 percent
*Cobble content--0 to 15 percent
*Organic carbon content--3 to 7 percent
*Thickness--25 to 50 cm
Bw and BC horizons
*Value--3 or 4 moist, 5 to 7 dry
*Chroma--2 to 6 moist, 3 or 4 dry
*Clay content--18 to 27 percent
*Total fragment content--35 to 70 percent
*Gravel content--30 to 60 percent
*Cobble content--0 to 30 percent
COMPETING SERIES:
Balsam--rock fragments are gneiss or granite; few to common mica flakes throughout the particle-size control section
Dougan--75 to 100 cm to lithic contact
Fernwood--50 to 100 cm to lithic contact
Scaredman--50 to 100 cm to lithic contact
Stackyards--averages 25 to 35 percent clay in the particle-size control section
Zygore--averages 8 to 18 percent clay in the particle-size control section
GEOGRAPHIC SETTING:
Elevation--790 to 1400 m
Climate--cool, wet winters; warm, dry summers
Mean annual precipitation--1400 to 2400 mm
Frost-free period--50 to 150 days
GEOGRAPHICALLY ASSOCIATED SOILS:
Coolcamp--andic soil properties throughout the particle-size control section; located on north-facing mountain slopes
Lempira--at least 36 cm of andic soil properties within 60 cm of the mineral soil surface; located on hillslopes and plateaus
Telemon--aquic conditions within 25 to 50 cm of the mineral soil surface; located on footslopes, benches and mountain slopes
Thistleburn--averages 40 to 55 percent clay in the particle-size control section; located on mountain slopes and benches
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--well drained
Flooding--none
Ponding--none
Saturated hydraulic conductivity (Ksat)--high
USE AND VEGETATION:
Use--timber production, wildlife habitat
Potential natural vegetation--western hemlock, sugar pine, white fir, Douglas-fir, Pacific rhododendron, western swordfern, red huckleberry, cascade barberry, redwood-sorrel, salal, vine maple, twinflower, giant chinkapin, pipsissewa, and whiteveined wintergreen
DISTRIBUTION AND EXTENT: Cascade Mountain Range, Oregon; MLRA 3; moderate extent
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Douglas County, Oregon, 1994
REMARKS:
Diagnostic horizons and features in this pedon
*Particle-size control section--zone from 28 to 103 cm
*Umbric epipedon--zone from 3 to 41 cm
*Cambic horizon--zone from 41 to 122 cm
*Andic subgroup feature--zone from 3 to 41 cm
11/2023--revised series concept from Typic Humudepts to Andic Humudepts, 13th edition of Keys to Soil Taxonomy, based on the correlation of ochric epipedons with nearby KSSL data failing andic subgroup critera (91P0753, 75C0071, 75C0070) and umbric epipedons with nearby KSSL data meeting andic subgroup criteria (12N7675).
National Cooperative Soil Survey
U.S.A.