LOCATION GUAM GU+PBEstablished Series
TAXONOMIC CLASS: Clayey, gibbsitic, nonacid, isohyperthermic
Lithic Ustorthents
TYPICAL PEDON: Guam cobbly clay loam, on a l percent slope under grazed shrubland. (Colors are for moist soil unless otherwise stated. Textures are apparent field textures.)
A--0 to 2 inches; dark reddish brown (2.5YR 3/4) cobbly clay loam; moderate very fine granular structure; friable, slightly sticky and slightly plastic; many very fine through coarse roots; many very fine tubular and interstitial pores; about 10 percent pebbles and 10 percent cobbles; neutral (pH 7.1); abrupt smooth boundary. (1.5 to 6 inches thick)
Bw--2 to 8 inches; dusky red (10R 3/4) gravelly clay loam; moderate very fine granular structure; very friable, slightly sticky and slightly plastic; many very fine and fine roots, few medium and coarse roots; common very fine tubular and interstitial pores; pressure faces on peds; about 20 percent pebbles and 5 percent cobbles; mildly alkaline (pH 7.5); abrupt irregular boundary. (4 to 16 inches thick)
2R--8 inches; coralline limestone, very porous; upper boundary ranges from 3 to 12 inches in pedon.
TYPE LOCATION: Guam; Fred Quitigua's farm, northeast portion, about 30 feet SE of main farm road, 330 feet SW of northern fenceline; about NE of Yigo church; lat. 13 degrees 31 minutes 50 seconds N. and long. l44 degrees 54 minutes 24 seconds E.
RANGE IN CHARACTERISTICS:
Soil moisture - Not continuously moist in the moisture control section for 90 to 120 cumulative days, primarily between February and May. Soil is usually moist from July through December.
Soil temperature - 77 to 86 degrees F., with less than 4 degrees F. variation between summer and winter.
Depth to bedrock - Dominantly 2 to 10 inches.
Percent clay - Laboratory determined clay content is 60 to 95 percent but apparent field texture feels like 35 to 55 percent due to the gibbsitic clay mineralogy.
A horizon - Color: Dominantly 2.5YR 3/4, 5YR 3/3, 3/4, ranges to 2.5YR 3/2, 3/3, 2/4, 4/4.
Texture: Gravelly clay loam, cobbly clay loam, gravelly clay. Structure: Granular or subangular blocky.
Rock fragments: 5 to 15 percent cobbles, 10 to 25 percent pebbles. Reaction: Neutral or mildly alkaline.
B horizon - Color: Dominantly 10R 3/4, 2.5YR 3/6, ranges to 10R 3/6, 2.5YR 3/4, 4/6, 5YR 3/4, 4/6, 4/8.
Texture: Gravelly clay loam, gravelly silty clay, gravelly clay, cobbly clay loam.
Structure: Granular or subangular blocky.
Rock fragments: 5 to 15 percent cobbles, 10 to 25 percent pebbles. Reaction: Neutral or mildly alkaline.
C horizon - Present in some pedons. Intermittent, 5YR, gravelly clay loam.
COMPETING SERIES: This is the Ritidian series that has more than 35 percent rock fragments.
GEOGRAPHIC SETTING: Gently sloping to strongly sloping limestone plateaus. Slopes range from 0 to 15 percent. These soils are on uplifted limestone plateaus, and formed in alluvium and slope alluvium from limestone mixed with volcanic ash, that overlie coralline limestone. Elevation is 30 to 800 feet. Mean annual precipitation ranges from 80 to 100 inches, most of which falls between June and November. Mean annual temperature is 79 degrees F., with less than 4 degrees F. difference between summer and winter.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Kagman, Pulantat, Saipan, Yigo, and the competing Ritidian soils. Kagman, Saipan, and Yigo soils are deep. Pulantat soils are 10 to 20 inches deep, have an argillic horizon with over 60 percent clay and have B horizon hues yellower than 5YR.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderately rapid permeability.
USE AND VEGETATION: Guam soils are used for urban development, row crops and as watershed and wildlife habitat. Areas not urbanized or cultivated are in forest.
DISTRIBUTION AND EXTENT: Northern Guam; the series is of moderate extent, with about 35,000 acres.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Guam; July 1985.
REMARKS: Diagnostic features recognized in this pedon are:
Ochric epipedon - From the surface to 6 inches.
Lithic contact - At 8 inches.
ADDITIONAL DATA: This pedon was characterized by the National Soil Survey Laboratory (sample #583-GU-066-016).