LOCATION STECUM MT+CA COEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed Typic Cryorthents
TYPICAL PEDON: Stecum coarse sandy loam, grassland (colors are for dry soil unless otherwise noted).
A1--0 to 5 inches; light brownish gray (10YR 6/2) coarse sandy loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure parting to weak coarse granular; slightly hard, very friable, nonsticky and nonplastic; common fine and very fine roots; common fine pores; 10 percent pebbles; neutral (pH 7.3); clear smooth boundary. (2 to 6 inches thick)
A2--5 to 12 inches; pale brown (10YR 6/3) loamy coarse sand, brown (10YR 4/3) moist; weak fine subangular blocky structure parting to weak coarse granular; slightly hard, very friable, nonsticky and nonplastic; few fine roots; few fine pores; 5 percent cobbles and 10 percent pebbles; neutral (pH 7.3); clear wavy boundary. (4 to 8 inches thick)
C--12 to 28 inches; light gray (2.5Y 7/2) gravelly coarse sand, pale brown (10YR 6/3) moist; massive; loose, very friable, nonsticky and nonplastic; few fine roots; 5 percent cobbles, 5 percent stones, and 35 percent pebbles; neutral (pH 7.3); abrupt smooth boundary. (14 to 30 inches thick)
Cr--28 inches; fractured and partly weathered micaceous granite and gneiss.
TYPE LOCATION: Ravalli County, Montana; 50 feet east and 2,600 feet north of the SW corner of sec. 1, T. 6 N., R. 20 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F. (mean summer--less than 59 degrees F.).
Moisture control section - approximately between the depths of 12 and 35 inches.
Control section - 0 to 5 percent clay and 35 to 60 percent rock fragments.
Rock fragments - granite and gneiss.
Depth to bedrock - 20 to 40 inches.
A1 horizon -
Value: 5 or 6 dry; 3 or 4 moist
Chroma: 2 or 3
Texture, less than 2 mm: coarse sandy loam or loamy coarse sand
Clay content: 5 to 15 percent
Rock fragments: 0 to 25 percent--0 to 15 percent cobbles and stones; 0 to 15 percent pebbles
Phases: stony and very stony
Reaction: pH 5.6 to 7.8
A2 horizon -
Value: 5 or 6 dry; 4 or 5 moist
Texture, less than 2 mm: loamy coarse sand or coarse sandy loam
Clay content: 5 to 10 percent
Rock fragments: 0 to 25 percent--0 to 10 percent cobbles and stones; 0 to 15 percent pebbles
Reaction: pH 5.6 to 7.8
NOTES: The base of this horizon is less than 10 inches when textures are coarse sandy loam.
C horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 2 or 3
Texture, less than 2 mm: coarse sand or loamy coarse sand
Clay content: 0 to 5 percent
Rock fragments: 35 to 60 percent--5 to 15 percent cobbles and stones; 30 to 45 percent pebbles
Reaction: pH 5.6 to 7.8
COMPETING SERIES: These are the Alflack (WY), Chena (AK), Chenega (AK), Cryomont (WA), Graylock (ID), Mirror Lake (UT), Nataga (AK), Nizina (AK), Obscurity (WA), Ovando (MT), Polepatch (WA), and Studebaker (WA) series. All of these soils are deep.
GEOGRAPHIC SETTING: The Stecum soils are on foothills of mountains. Elevations are 3,500 to 6,000 feet. Slopes are 0 to 70 percent. These soils formed in materials weathered from micaceous granite and gneiss bedrock. The climate is characterized by long, cold winters; moist springs; and warm summers. Mean annual precipitation is 15 to 19 inches. Mean annual temperature is about 40 to 45 degrees F. The frost-free period is 60 to 90 days.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; rapid permeability.
USE AND VEGETATION: Stecum soils are used mainly as rangeland. Potential native vegetation is mainly Idaho fescue, western wheatgrass, needleandthread, antelope bitterbrush, Sandberg bluegrass, bluebunch wheatgrass, and rough fescue.
DISTRIBUTION AND EXTENT: Stecum soils are extensive in Montana, Colorado, and Wyoming.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Ravalli County, Montana, 1954.
REMARKS: Soil Interpretations Record: MT0551. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the surface to 7 inches (A1, A2 horizons); a particle-size control section from 10 to 28 inches. Stecum soils have a cryic temperature regime and an ustic moisture regime.