LOCATION ARBORETUM AZ
Established Series
Rev. JMH/JMP
02/2025
ARBORETUM SERIES
The Arboretum series consists of deep and very deep, well drained soils that formed in deposits derived from benmoreite, or dacite. Arboretum soils are on playa, alluvium, or slope alluvium deposits. Slopes range from 0 to 8 percent. Mean annual precipitation is 20 to 23 inches and the mean annual temperature is about 48 degrees F.
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Pachic Argiustolls
TYPICAL PEDON: Flagwell-Arboretum complex (Colors are for dry soil unless otherwise noted.)
A1--0 to 3 inches, (0 to 8 cm); black (10YR 2/1) sandy clay loam, black (7.5YR 2.5/1), moist; strong medium granular; soft, very friable, moderately sticky, moderately plastic; common coarse, and few fine dendritic tubular pores; many very fine, and common fine roots throughout; 5 percent gravel; noneffervescent; neutral (pH 7.2); clear smooth boundary
A2--3 to 9 inches, (8 to 22 cm); black (10YR 2/1) clay loam, black (10YR 2/1), moist; moderate fine subangular blocky; slightly hard, friable, moderately sticky, moderately plastic; few fine and common medium dendritic tubular pores; many very fine, common fine, and common medium roots throughout; 5 percent gravel; noneffervescent; neutral (pH 7.2); gradual smooth boundary
Bt1--9 to 26 inches, (22 to 66 cm); very dark grayish brown (10YR 3/2) clay loam, black (10YR 2/1), moist; weak fine subangular blocky; slightly hard, friable, very sticky, very plastic; few very fine and fine dendritic tubular pores, common very fine and fine roots throughout; 30 percent faint clay films on all faces of peds; 10 percent gravel; noneffervescent; slightly alkaline (pH 7.4); diffuse smooth boundary
Bt2--26 to 35 inches, (66 to 90 cm); brown (7.5YR 4/4) clay, brown (7.5YR 4/4), moist; weak fine subangular blocky; hard, friable, moderately sticky, moderately plastic; few very fine roots throughout; 20 percent faint clay films on all faces of peds; 5 percent gravel; very slight effervescence; slightly alkaline (pH 7.4); diffuse boundary
Bt3--35 to 62 inches, (90 to 157 cm); brown (7.5YR 4/4) sandy clay loam, brown (7.5YR 4/3), moist; weak fine subangular blocky, friable, slightly sticky, moderately plastic; few very fine roots throughout; 20 percent faint clay films on all faces of peds; 10 percent gravel; noneffervescent; neutral (pH 7.2); diffuse boundary
Bt4--62 to 76 inches, (157 to 197 cm); brown (7.5YR 4/4) sandy clay loam, brown (7.5YR 4/3), moist; weak fine subangular blocky; friable, slightly sticky, moderately plastic; few very fine roots throughout; 10 percent faint clay films on all faces of peds; 10 percent gravel; very slight effervescence; slightly alkaline (pH 7.4)
TYPE LOCATION: Coconino County, Arizona; located about 8.0 kilometers (5.0 miles) southwest of Flagstaff, Arizona; USGS Quadrangle Flagstaff West; Latitude 35.1624167, Longitude -111.7318889, Datum WGS84.
RANGE IN CHARACTERISTICS:
Soil moisture regime: typic ustic
Mean annual soil temperature: 47 to 51 degrees F
Rock fragment content: 0 to 15 percent
Depth to lithic contact: more than 100 centimeters
Particle-size control section: fine
Clay content: 35 to 45 percent
A horizon
Hue: 7.5YR or 10YR
Value: 2 to 4, dry or moist
Chroma: 1 to 3, dry or moist
Calcium carbonate equivalent: 0 to 2 percent
Reaction: neutral or slightly alkaline
Bt horizons
Hue: 7.5YR or 10YR
Value: 3 or 4, dry or moist
Chroma: 1 to 4, dry or moist
Texture: clay loam, clay, or sandy clay loam
Calcium carbonate equivalent: 0 to 2 percent
Sodium Adsorption Ratio (SAR): 0 to 2
Reaction: neutral or slightly alkaline
COMPETING SERIES: None.
GEOGRAPHIC SETTING:
Parent material: alluvium derived from benmoreite or dacite
Landform: weathered lava fields
Slopes: 0 to 8 percent
Elevation: 6,300 to 7,900 feet
Mean annual air temperature: 45 to 49 degrees F
Mean annual precipitation: 18 to 22 inches
Precipitation peaks in July and August, and in winter months. May and June are much drier.
Frost-free period: 100 to 120 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Flagwell, Pluto, Purpleheart, and Procky soils. Flagwell soils are derived from benmoreite or dacite in residuum having less clay than soils derived from basalt. Pluto, Purpleheart and Procky soils are from basalt lava flows.
DRAINAGE AND PERMEABILITY: well drained, moderately slow permeability
USE AND VEGETATION: These soils are used principally as grazing land. Native vegetation is mainly Arizona fescue, blue grama, and mountain muhly.
DISTRIBUTION AND EXTENT: Northern Arizona. MLRA 39.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Coconino County, Arizona.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon: from 0 to 66 centimeters. (A and Bt1 horizons)
Argillic horizon; from below 22 centimeters (Bt2 through Bt4 horizon)
Name is derived from nearby Arboretum of Flagstaff
Taxonomic Version: Keys to Soil Taxonomy, Thirteenth Edition, 2022
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National Cooperative Soil Survey
U.S.A.