LOCATION TOLBERT MTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Lithic Argiustolls
TYPICAL PEDON: Tolbert very cobbly loam, bouldery, in rangeland (colors are for dry soil unless otherwise noted).
A--0 to 7 inches; dark grayish brown (10YR 4/2) very cobbly loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine interstitial pores; 30 percent cobbles, 10 percent pebbles; neutral (pH 6.6); clear wavy boundary. (4 to 8 inches thick)
Bt--7 to 12 inches; brown (10YR 5/3) very cobbly clay loam, brown (10YR 4/3) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; many very fine and fine roots; many very fine and fine interstitial and tubular pores; common distinct dark grayish brown (10YR 4/2) clay films on faces of peds and bridging sand grains; 40 percent cobbles, 15 percent pebbles; neutral (pH 6.8). (5 to 15 inches thick)
R--12 inches; hard fine grained igneous rock.
TYPE LOCATION: Jefferson County, Montana; 300 feet north and 2,600 feet east of the SW corner of sec. 4, T. 5 N., R. 3 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 38 to 47 degrees F.
Moisture control section - between 4 and 12 inches or between 4 inches and the lithic contact if bedrock is less than 12 inches; frozen during winter months.
Mollic epipedon thickness - 7 to 16 inches.
Depth to argillic horizon - 5 to 8 inches.
Depth to bedrock - 10 to 20 inches.
Surface stones or boulders - 0 to 3 percent
A transition BC horizon is allowed.
A horizon - Hue: 7.5YR, 10YR or 2.5Y
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 or 3
Texture: Loam or clay loam
Clay content: 15 to 35 percent
Rock fragments: 15 to 80 percent--0 to 25 percent stones, 0 to 30 percent cobbles, and 5 to 65 percent pebbles or channers
Reaction: pH 6.6 to 7.8
Bt horizon - Hue: 5YR, 7.5YR, 10YR or 2.5Y
Value: 3, 4 or 5 dry; 2, 3 or 4 moist
Chroma: 2, 3, or 4
Texture: loam, clay loam or sandy clay loam
Clay content: 20 to 35 percent
Rock fragments: 35 to 80 percent--0 to 5 percent stones, 20 to 45 percent cobbles, and 15 to 30 percent pebbles
Reaction: pH 6.6 to 7.8
COMPETING SERIES:
Bushvalley (AZ) is driest in the soil moisture control section during May and June; formed in alluvium from pyroclastics; 2R horizon consists of tuff.
Gnojek (MT) - has a horizon of secondary carbonate accumulation.
Owlrock (NM) - has horizons of secondary carbonate accumulation.
Teaspoon (CO) - moist is all parts of the moisture control section for 60 or more consecutive days after July 15.
Tolman (WY) - has an intermittent BA horizon; reaction ranges to moderately alkaline; allows a Btk horizon above sandstone with carbonaceous shale.
Zibetod (AZ) - is moist in the moisture control section from January to May.
GEOGRAPHIC SETTING:
Landform - sedimentary plains; hills; mountains.
Elevation - 3,500 to 7,700 feet.
Slope - 2 to 70 percent.
Parent material - colluvium or residuum derived from hard fine grained sandstone, fine grained igneous rock or interbedded sandstone and shale.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 15 to 23 inches.
Mean annual air temperature - 36 to 45 degrees F.
Frost-free period - 70 to 115 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Blaincreek, Sawicki, and Shawmut soils. Blaincreek soils are moderately deep to a lithic contact. Shawmut and Sawicki soils are very deep.
DRAINAGE AND PERMEABILITY: Well drained, moderate permeability.
USE AND VEGETATION: Tolbert soils are primarily used for rangeland, woodland, and wildlife habitat. The potential native vegetation is mainly Idaho fescue, rough fescue, bluebunch wheatgrass, sandberg bluegrass, prairie junegrass, lupine, stoneseed, big sagebrush, and Rocky Mountain juniper. Areas in woodland have an overstory of Douglas fir, limber pine, or ponderosa pine and an understory of rough fescue, Idaho fescue, bluebunch wheatgrass, big sagebrush, and Rocky Mountain juniper.
DISTRIBUTION AND EXTENT: Tolbert soils are of small extent in southwestern Montana.
MLRA OFFICE RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Powell County, Montana, 1995; Series proposed Jefferson County, Montana, 1993.
REMARKS: Soil interpretation record: MT1584, MT3059. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the surface to 7 inches (A horizon); an argillic horizon from 7 to 12 inches (Bt horizon); a particle size control section from the surface to 12 inches (A, Bt horizons); hard fine grained igneous bedrock at 12 inches (R horizon). Tolbert soils have a frigid temperature regime and an ustic moisture regime.