LOCATION THREETREES OREstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Typic Dystrudepts
TYPICAL PEDON: Threetrees very channery loam - woodland, on a 16 percent south-facing slope at 2,890 feet elevation. (When described on July 26, l989, the soil was dry to 13 inches and moist below this depth. Colors are for moist soil unless otherwise noted.)
0i--1 inch to 0; partially decomposed needles, leaves, twigs, and woody materials.
A--0 to 7 inches; strong brown (7.5YR 4/6) very channery loam, brownish yellow (10YR 6/6) dry; moderate fine and very fine subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; common fine and medium, and few coarse roots; many fine and medium tubular pores; 35 percent channers and 5 percent flagstones; extremely acid (pH 4.4); clear smooth boundary. (3 to 8 inches thick)
AB--7 to 13 inches; strong brown (7.5YR 4/6) very channery loam, brownish yellow (10YR 6/8) dry; moderate fine and medium subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; common fine and medium, and few coarse roots; many fine and medium tubular pores; 35 percent channers and 10 percent flagstones; very strongly acid (pH 4.8); clear smooth boundary. (0 to 6 inches thick)
Bw1--13 to 22 inches; dark yellowish brown (10YR 4/6) very channery clay loam, brownish yellow (10YR 6/8) dry; moderate medium subangular blocky structure; slightly hard, firm, sticky and slightly plastic; common fine and medium roots; many fine and medium tubular pores; 30 percent channers and 15 percent flagstones; strongly acid (pH 5.1); gradual smooth boundary.
Bw2--22 to 33 inches; yellowish brown (10YR 5/6) very flaggy clay loam, brownish yellow (10YR 6/8) dry; moderate fine and medium subangular blocky structure; slightly hard, firm, sticky and slightly plastic; common fine and medium roots; many fine and medium tubular pores; 30 percent flagstones and 20 percent channers; strongly acid (pH 5.4); gradual wavy boundary.
Bw3--33 to 37 inches; brownish yellow (10YR 6/6) very flaggy clay loam, yellow (10YR 8/6) dry; moderate medium subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; few fine and medium roots; many fine and medium tubular pores; 35 percent flagstones and 20 percent channers; strongly acid (pH 5.4); abrupt wavy boundary. (Combined thickness of the Bw horizon ranges from 17 to 26 inches)
R--37 inches; fractured schist.
TYPE LOCATION: Curry County, Oregon; about 330 feet south and 2,310 feet west of the northeast corner of section 31, T. 37 1/2 S., R. 12 W. (Latitude 42 degrees, 18 minutes, 28 seconds N.; Longitude 124 degrees, 09 minutes, 36 seconds W.)
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 41 to 46 degrees F. The soils are usually moist and are dry for less than 45 consecutive days in all parts between depths of 4 and 12 inches in the four months following the summer solstice. The particle-size control section averages 27 to 35 percent clay and 35 to 85 percent rock fragments. Depth to bedrock and solum thickness is 20 to 40 inches. Hue is 10YR or 7.5YR.
The A horizon has value of 4 to 6 moist, 5 to 7 dry and chroma of 4 to 6 moist and dry. It is very channery loam with 20 to 25 percent clay. It has 30 to 40 percent channers, 5 to 10 percent flagstones and 0 to 5 percent stones. It is extremely to very strongly acid throughout.
The Bw horizon has value of 4 to 6 moist, 6 to 8 dry and chroma of 6 to 8 moist and dry. It is very channery clay loam, extremely channery clay loam or very flaggy clay loam with 27 to 35 percent clay. It has 20 to 40 percent channers, 15 to 40 percent flagstones and 0 to 5 percent stones. It is very strongly to strongly acid throughout.
COMPETING SERIES: These are the Lagross, Macomber, Mandy, Mosinee, Rilea (T), Saddlepeak (T), and Vly series. Lagross, Macomber, Mandy, Mosinee and Vly soils average less than 27 percent clay in the particle-size control section. Lagross, Mosinee and Saddlepeak soils are greater than 40 inches deep to bedrock. Rilea soils have angular-shaped rock fragments throughout the solum which are metasedimentary or metavolcanic in origin.
GEOGRAPHIC SETTING: Threetrees soils are on metastable broad ridgetops and active side slopes of mountains. Slopes are 0 to 90 percent. The soils formed in colluvium and residuum derived from schist or phyllite rock types of the Colebrooke Schist Formation. Elevations are 2,500 to 4,500 feet. The climate is characterized by cool wet winters and warm moist summers. The mean annual precipitation is 130 to 160 inches. The mean annual temperature is 40 to 45 degrees F. The frost-free period is 60 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Coffeebutte (T), Saddlepeak (T), Scalerock (T) and Soldiercamp (T) soils. Coffeebutte and Soldiercamp soils have umbric epipedons and occur in open grassland areas on broad ridgetops and south-facing side slopes of mountains. In addition, Coffeebutte soils are 20 to 40 inches deep to bedrock and Soldiercamp soils are 10 to 20 inches deep to bedrock. Saddlepeak and Scalerock soils occur on broad ridgetops and side slopes of mountains. In addition, Saddlepeak soils are greater than 60 inches deep to bedrock and Scalerock soils are 10 to 20 inches deep to bedrock.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: These soils are used mainly for timber production, watershed, recreation and wildlife habitat. The native vegetation is Douglas fir, tanoak, golden chinkapin, Pacific madrone, canyon live oak, Pacific rhododendron, evergreen huckleberry, red huckleberry, salal, western swordfern, common beargrass, cascade Oregongrape, Sadler oak, western brackenfern and evergreen violet.
DISTRIBUTION AND EXTENT: Mountainous areas of southwestern Oregon; MLRA 1. The series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES PROPOSED: Curry County, Oregon, 1991. The source of the name is Threetrees Mountain in southern Curry County.
REMARKS: Diagnostic horizons and features recognized in this pedon include:
Ochric epipedon -
Cambic horizon - from a depth of 13 to 37 inches (Bw1, Bw2, Bw3 horizons).
Particle-size control section - from a depth of 10 to 37 inches (lower part of AB horizon, Bw1, Bw2, and Bw3 horizons) with a weighted average of 40 percent rock fragments.
ADDITIONAL DATA: Partial laboratory data available for pedon 90P 306, sample 90P1900 from Curry County, Oregon sampled by NSSL at Lincoln, Nebraska - 3/90.