LOCATION PINEBREAKS MTEstablished Series
TAXONOMIC CLASS: Clayey, smectitic, acid, frigid, shallow Typic Ustorthents
TYPICAL PEDON: Pinebreaks silty clay, woodland. (Colors are for dry soil unless otherwise noted)
Oi--2 to 0 inches; partially decomposed forest litter.
A--0 to 3 inches; grayish brown (2.5Y 5/2) silty clay, dark grayish brown (2.5Y 4/2) moist; moderate fine granular structure; slightly hard, friable, sticky and plastic; common medium, fine and very fine roots; slightly acid (pH 6.2); clear wavy boundary. (1 to 4 inches thick)
Bw--3 to 8 inches; light brownish gray (2.5Y 6/2) silty clay, dark grayish brown (2.5Y 4/2) moist; weak medium subangular blocky structure; very hard, firm, very sticky and very plastic; common coarse, medium, fine, and very fine roots; many very fine pores; 10 percent soft shale fragments; slightly acid (pH 6.4); clear wavy boundary. (3 to 8 inches thick)
BC--8 to 18 inches; light brownish gray (2.5Y 6/2) silty clay, dark grayish brown (2.5Y 4/2) moist; massive; slightly hard, friable, very sticky and very plastic; common coarse, medium, fine, and very fine roots between shale fragments; 70 percent soft shale fragments; very strongly acid (pH 4.8); diffuse wavy boundary. (6 to 14 inches thick)
Cr--18 to 60 inches; grayish brown (2.5Y 5/2) consolidated shale, dark gray (N 4/0) moist; very strongly acid. (pH 4.6)
TYPE LOCATION: Petroleum County, Montana; 1,700 feet west and 1,150 feet north of the SE corner of sec. 31, T. 21 N., R. 27 E.
RANGE IN CHARACTERISTICS:
Soil temperature: 42 to 47 degrees F.
Moisture control section: approximately between the depths of 4 and 12 inches.
Soil reaction: pH less than 5.5 in the control section.
Depth to shale: 10 to 20 inches.
Notes: Pinebreaks soils occur on sites having substantially higher effective precipitation than surrounding areas due to the combined influence of aspects and steep slopes.
A horizon: hue: 10YR or 2.5Y
Value: 4, 5 or 6 dry, 3, 4, or 5 moist
Chroma: 1, 2 or 3
Texture: less than 2 mm: clay, silty clay or silty clay loam.
Clay content: 35 to 50 percent
EC: less than 2 mmhos/cm
Reaction: pH 5.6 to 7.8
Bw horizon: hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 1, 2, or 3
Texture: less than 2 mm: clay or silty clay
Clay content: 40 to 60 percent
Rock fragments: 5 to 25 percent soft shale fragments
EC: less than 2 mmhos/cm
Reaction: pH 5.6 to 7.8
BC horizon: hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 1, 2 or 3
Texture: less than 2 mm: clay or silty clay
Clay content: 40 to 60 percent
Rock fragments: 60 to 90 percent soft shale fragments
EC: less than 2 mmhos/cm
Reaction: pH 4.5 to 5.5.
Cr horizon: The shale fragments are very hard or hard when dry and very firm when moist
Reaction: pH 4.5 to 5.5
Notes: tree roots utilize the upper portion of the Cr horizon by growing between shale fragments.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: The Pinebreaks soils are on steep north facing slopes and in narrow north facing ravines on uplands. Elevations are 1,900 to 4,000 feet. Slopes are 15 to 60 percent. Pinebreaks soils formed in material derived from consolidated shale. The climate is cool, with moist springs and hot dry summers and long cold winters. Mean annual precipitation is 10 to 14 inches. Mean annual air temperature is 40 to 45 degrees F. The frost-free period is 100 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; very rapid runoff; slow permeability.
USE AND VEGETATION: Pinebreaks soils are used mainly for wildlife habitat and understory grazing. The overstory is comprised of Rocky Mountain Douglas-fir and ponderosa pine. Rocky Mountain juniper, bluebunch wheatgrass, and western snowberry are the primary understory plants, often there is a dense carpet of moss and lichens.
DISTRIBUTION AND EXTENT: Pinebreaks soils are mainly in central Montana. The series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Petroleum County, Montana, 1996.
REMARKS: Soil Interpretation Record: MT1113.
Diagnostic horizons and features recognized in this pedon are: ochric epipedon - from the soil surface to a depth of 7 inches (A and Bw horizons); paralithic contact - at 18 inches; particle-size control section - from 10 to 18 inches (BC horizon). Pinebreaks soils have an frigid temperature regime and an ustic moisture regime bordering on aridic.