LOCATION BREWSTER TXEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Aridic Lithic Haplustolls
TYPICAL PEDON: Brewster extremely gravelly loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 8 inches; brown (7.5YR 5/3) extremely gravelly loam, dark brown (7.5YR 3/3) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many fine roots; 70 percent rhyolite rock fragments of which 40 percent are gravel, 20 percent are cobbles and 10 percent are stones; neutral; abrupt boundary. (4 to 20 inches thick)
R--8 to 60 inches; fractured rhyolitic bedrock.
TYPE LOCATION: Brewster County, Texas; From the intersection of US Highway 90 and Texas Highway 118 in Alpine, 3.2 miles south on Texas Highway 118, 0.6 miles south and east on ranch trail, 50 feet south in range; near midpoint of south boundary of Section 106, G.H. & S.A. Ry. Co. Block 9. Bird Mountain USGS 7.5 minute topoqraphic quadrangle; at Latitude 30 degrees, 19 minutes, 06 seconds North, Longitude 103 degrees, 37 minutes, 13 seconds West, NAD27. UTM coordinates: 632744m E, 3364845m N, Zone 13N, NAD83.
RANGE IN CHARACTERISTICS:
Soil moisture: aridic ustic moisture regime
Solum thickness and depth to hard bedrock: 4 to 20 inches
Rock fragments: 35 to 80 percent by volume and are 25 to 70 percent gravel, 0 to 25 percent cobbles and 0 to 20 percent stones
Reaction: slightly alkaline to slightly acid
A horizon
Hue: 5YR, 7.5YR, 10YR
Value: 3 through 5, dry or moist
Chroma: 2 or 3, dry or moist
Texture: loam, silt loam, clay loam
Clay content: 18 to 35 percent clay
Other features: few films or distinct coatings of calcium carbonate are on the faces of the fracture planes in the bedrock in some pedons
Secondary calcium carbonate: less than 5 percent
R layer
Rock fragments: mostly rhyolitic, trachytic, and basaltic rocks
COMPETING SERIES: This is the Budlamp (AZ), Canquya (AZ), Siphoncan (AZ), and Yarbam (AZ) series. Budlamp soils have less than 18 percent clay in the control section. Yarbam soils are calcareuos throughout and contain 20 to 40 percent calcium carbonate equivalent. Canquya and Siphoncan soils are inactive.
GEOGRAPHIC SETTING: Brewster soils are on igneous hills and mountains. Slopes range from 5 to about 90 percent. The regolith consists of a thin mantle of loamy earth, containing many coarse fragments. Underlying rocks are fine grained igneous rocks. Rock outcrops are common on slopes of more than 20 percent. Mean annual precipitation ranges from 12 to 20 inches, the majority coming in late spring and in summer. Mean annual air temperature ranges from 57 to 64 degrees F. Frost free period is 140 to 240 days, and the elevation is 4,000 to 6,300 feet.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Boracho, Ector, Espy, Kokernot, Liv, Mainstay, Medley, Santo Tomas and Volco series. Volco soils are in similar positions. Boracho and Espy soils have a petrocalcic horizon. Ector soils formed in limestone. Kokernot soils are in a loamy family and do not have a mollic epipedon. Liv and Mainstay soils have a clayey-skeletal argillic horizon. Medley and Santo Tomas soils are deeper than 20 inches to bedrock.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderately slow. Runoff is medium on 5 to 20 percent slopes, and high on slopes greater than 20 percent.
USE AND VEGETATION: Nearly all of this soil is used for livestock grazing. Native vegetation consists of short and mid grasses and in places a few low desert shrubs. Grasses are mainly grama, bluestem, muhly, threeawn, and lovegrass. Woody vegetation is juniper, scrubby oak trees and catclaw.
DISTRIBUTION AND EXTENT: Trans-Pecos area of Southwest Texas, MLRA 42. The soil is extensive.
MLRA OFFICE RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Brewster County, Texas; 1928.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from 0 to 8 inches (A horizon)
Lithic contact - The boundary at 8 inches (R horizon)
Classification changed from loamy-skeletal, mixed, superactive, thermic Lithic Haplustolls to loamy-skeletal, mixed, superactive, thermic Aridic Lithic Haplustolls in 2006.
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006
Update and revisions for the recorrelation of Brewster County, Texas, Main Part, 2/8/08, CEM