LOCATION GRASSMOUNTAIN OREstablished Series
TAXONOMIC CLASS: Fine-loamy, isotic, frigid Andic Dystrudepts
TYPICAL PEDON: Grassmountain gravelly medial loam - woodland, on a 32 percent northwest-facing slope at 2,280 feet elevation. (Colors are for moist soil unless otherwise noted. When described on September 12, 2000 the soil was moist throughout.)
Oi--0 to 1 inch; slightly decomposed plant material; abrupt wavy boundary.
A--1 to 7 inches; dark brown (7.5YR 3/3) gravelly medial loam, brown (7.5YR 4/3) dry; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; moderately smeary; many very fine, fine, and medium and few coarse roots; many very fine and fine tubular pores; 20 percent gravel and 2 percent cobbles; 5 percent paragravel; very strongly acid (pH 4.8); clear wavy boundary. (4 to 6 inches thick)
AB--7 to 15 inches; dark brown (7.5YR 3/4) paragravelly medial loam, brown (7.5YR 4/4) dry; weak fine subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; weakly smeary; many very fine, fine and medium, and few coarse roots; many very fine and fine tubular pores; 10 percent gravel; 15 percent paragravel and 5 percent paracobbles; very strongly acid (pH 5.0); clear smooth boundary. (3 to 8 inches thick)
Bw1--15 to 29 inches; strong brown (7.5YR 4/6) paragravelly loam, strong brown (7.5YR 5/6) dry; moderate fine subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; common very fine, fine and medium, and few coarse roots; many very fine and fine tubular pores; 10 percent gravel; 15 percent paragravel and 5 percent paracobbles; strongly acid (pH 5.2); gradual smooth boundary.
Bw2--29 to 44 inches; strong brown (7.5YR 5/6) very paragravelly clay loam, reddish yellow (7.5YR 6/6) dry; moderate fine and medium subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; common very fine, fine, and medium, and few coarse roots; common very fine and fine tubular pores; 10 percent gravel; 10 percent paracobbles and 20 percent paragravel; strongly acid (pH 5.2); gradual smooth boundary. (Combined thickness of the Bw horizon is 30 to 36 inches)
BCt--44 to 69 inches; reddish yellow (7.5YR 6/6) very paragravelly clay loam, reddish yellow (7.5YR 7/6) dry; weak medium and coarse subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; few very fine, fine, medium, and coarse roots; common very fine and fine tubular pores; few faint clay films on ped faces, surfaces of pores, and coating some rock fragments; 10 percent gravel; 15 percent paracobbles and 40 percent paragravel; strongly acid (pH 5.4); clear wavy boundary. (23 to 30 inches thick)
Crt--69 inches; weakly cemented, highly weathered sandstone and siltstone bedrock; fractured at intervals of 4 to less than 18 inches; few coarse roots in cracks; common distinct clay films coat some pararock fragments and occur along fracture planes.
TYPE LOCATION: Benton County, Oregon; approximately 2 miles west of Grass Mountain; located about 2,000 feet north and 2,350 feet west of the southeast corner of section 19, T. 13S., R. 8W. (Latitude 44 degrees, 25 minutes, 28 seconds N.; Longitude 123 degrees, 42 minutes, 29 seconds W.; Grass Mountain, OR 7.5 minute USGS Quad; NAD 1927)
RANGE IN CHARACTERISTICS:
Soil moisture: Udic moisture regime
Mean annual soil temperature: 43 to 47 degrees F. and the mean summer soil temperature is above 47 degrees F. with an O horizon present.
Solum thickness: 5 to 6 feet
Depth to bedrock: 60 to 80 inches to weakly cemented, highly weathered paralithic contact
Particle-size control section:
Clay content - 20 to 30 percent apparent clay content (field estimate)
Coarse fragments - 5 to 30 percent rock fragments; 20 to 50 percent pararock fragments
Hue: 10YR or 7.5YR
Soil reaction: Very strongly acid or strongly acid
A horizon
Value: 2 or 3 moist, 3 or 4 dry
Chroma: 2 to 4 moist and dry
Texture: GR-medial L
Clay content: 12 to 20 percent
Rock fragments: 15 to 20 percent gravel and 0 to 5 percent cobbles
Pararock fragments: 0 to 5 percent paragravel and 0 to 5 percent paracobbles
Organic matter content: 5 to 10 percent
Andic features: moist bulk density of 0.80 to 1.0 grams per cubic centimeter, phosphate retention of 80 percent or greater, acid-oxalate extractable aluminum plus one-half iron of 1.0 to 2.0 percent, and 15-bar moisture (air-dried) of 15 to 30 percent
Other features: The horizon has moderately smeary or weakly smeary consistence (field estimate).
AB horizon
Value: 3 or 4 moist, 4 or 5 dry
Chroma: 4 to 6 moist and dry
Texture: PGR-medial L, GR-medial L
Clay content: 18 to 25 percent
Rock fragments: 10 to 20 percent gravel and 0 to 3 percent cobbles
Pararock fragments: 0 to 20 percent paragravel and 0 to 5 percent paracobbles
Andic features: moist bulk density of 0.90 to 1.0 grams per cubic centimeter, phosphate retention of 75 percent or greater, acid-oxalate extractable aluminum plus one-half iron of 1.0 to 2.0 percent, and 15-bar moisture (air-dried) of 15 to 30 percent occur in this horizon
Bw horizon
Value: 4 or 5 moist, 4 to 7 dry
Chroma: 4 to 6 moist and dry
Texture: PGR-L, PGRV-CL, or PCBV-SICL
Clay content: 20 to 30 percent
Rock fragments: 5 to 10 percent gravel and 0 to 5 percent cobbles
Pararock fragments: 15 to 20 percent paragravel and 5 to 20 percent paracobbles
BCt or BC horizon
Value: 5 or 6 moist, 6 to 8 dry
Chroma: 4 to 6 moist and dry
Texture: PGRV-CL, PGRX-L, or PCBV-SICL
Clay content: 20 to 30 percent
Rock fragments: 5 to 10 percent gravel and 0 to 5 percent cobbles
Pararock fragments: 25 to 50 percent paragravel and 10 to 25 percent paracobbles
COMPETING SERIES: These are the
Fiverivers ,
Leopold,
Memaloose,
Oldblue,
Wilhoit, and
Xeno series.
Fiverivers (OR) - paralithic bedrock contact at 20 to 40 inches
Leopold(OR) - lithic bedrock contact at 20 to 40 inches
Memaloose (OR) - paralithic bedrock contact at 20 to 40 inches; hue is 5YR or 2.5YR; parent material is tuffs and breccias
Oldblue (OR) - umbric epipedon 15 to 25 inches thick; greater than 60 inches deep to paralithic bedrock contact
Wilhoit (OR) - paralithic bedrock contact at 40 to 60 inches; umbric epipedon 20 to 34 inches thick
Xeno (WA) - paralithic bedrock contact at 40 to 60 inches; umbric epipedon 10 to 20 inches thick
GEOGRAPHIC SETTING:
Parent material: Loamy colluvium and residuum derived from sandstone and siltstone of the Tyee or Flournoy Formations
Landform: Mountains
Landform position: Summits, backslopes, footslopes, and toeslopes
Slopes: 5 to 60 percent
Elevation: 1,800 to 3,000 feet
Climate: Cool, wet winters; warm, moist summers
Mean annual temperature: 42 to 46 degrees F
Mean annual precipitation: 90 to 130 inches
Frost free period: 70 to 120 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are
Blodgett,
Burntwoods,
Chintimini,
Fiverivers,
Luckiamute,
Lurnick,
Maryspeak and
Oldblue soils. Blodgett, Burntwoods, Chintimini, Fiverivers, and Oldblue soils occur on summits and side slopes of mountains. Luckiamute, Lurnick, and Maryspeak soils occur in a cryic temperature regime on adjacent higher mountain slopes.
Blodgett - loamy-skeletal; less than 20 inches deep to Cr over R contact
Burntwoods - medial-skeletal over loamy-skeletal; greater than 60 inches to bedrock
Chintimini - loamy-skeletal; 40 to 60 inches deep to Cr over R contact
Fiverivers - fine-loamy; 20 to 40 inches deep to a paralithic contact
Luckiamute - loamy-skeletal; less than 20 inches deep to a lithic contact
Lurnick - clayey-skeletal; 20 to 40 inches deep to a paralithic contact
Maryspeak - sandy-skeletal; greater than 80 inches deep
Oldblue - fine-loamy; 40 to 80 percent pararock fragments
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: These soils are used for timber production, recreation, wildlife habitat, and watersheds. Potential native vegetation is western hemlock, Douglas fir, Pacific rhododendron, cascade Oregongrape, cascade buckthorn, western swordfern, vine maple, baldhip rose, thimbleberry, salal, brackenfern, common beargrass, blackberry and red huckleberry. Scattered amounts of noble fir, Pacific silver fir, and tall blue huckleberry occur in some areas at the higher elevations within the frigid zone and are recognized as cool phases.
DISTRIBUTION AND EXTENT: Central portion of the Coast Range Mountains in Oregon; MLRA 1. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Benton County, Oregon, 2004. The name is taken from Grass Mountain in western Benton County.
REMARKS: Diagnostic horizons and features recognized in this pedon include:
Ochric epipedon
Cambic horizon - from depths of 15 to 44 inches (Bw1, Bw2 horizons).
Andic feature - from 1 to 15 inches (A and AB horizons). Based on lab data and field observations.
Medial modifiers were used for those horizons meeting the andic subgroup criteria although not meeting andic soil properties. A proposal was submitted to NSSC (2000) to revise the definition of medial to also include those soil properties qualifying for the Andic subgroup under criteria #1 for andic soil properties.
Particle-size control section (fine-loamy family) - from 11 to 41 inches (1 inch of AB horizon, all of Bw1 and Bw2 horizons, and 2 inches of the BCt horizon).
Evidence of translocated clay - few faint clay films are present in this soil; however, the clay increase is not significant enough to qualify as an argillic horizon.
Depths to diagnostic horizons and features are measured from the top of the first mineral layer.
Official type location and pedon moved at final correlation to more accurately reflect the modal concept.