LOCATION AUA AS PBEstablished Series
The Aua series consists of deep, well drained soils on talus slopes. These soils formed in colluvium and alluvium derived from material weathered from basic igneous rock. Slope is 15 to 60 percent. Elevation is near sea level to 650 feet. The mean annual rainfall is about 200 inches, and the mean annual temperature is about 79 degrees F.
TAXONOMIC CLASS: Clayey-skeletal, mixed, superactive, isohyperthermic Pachic Hapludolls
TYPICAL PEDON: Aua very stony silty clay loam - on a 35 percent talus slope on a roadside. When described the soil was moist throughout. (Colors are for moist soil unless otherwise stated. Textures are apparent field textures.)
A--0 to 7 inches; dark brown (7.5YR 3/2) very stony silty clay loam, brown (7.5YR 4/4) dry; strong medium and fine subangular blocky structure; extremely hard, friable, slightly sticky and slightly plastic; many roots; many pores; 25 percent stones, 5 percent cobbles, and 10 percent pebbles; neutral (pH 6.6); clear smooth boundary. (6 to 11 inches thick)
Bw1--7 to 18 inches; dark brown (7.5YR 3/3) stony clay loam, brown (7.5YR 4/2) dry; moderate medium and fine subangular blocky structure; extremely hard, firm, very sticky and very plastic; many roots; many very fine and common fine pores; 20 percent stones, 5 percent cobbles, and 5 percent pebbles; neutral (pH 6.6); gradual smooth boundary. (8 to 14 inches thick)
Bw2--18 to 39 inches; dark brown (7.5YR 3/3) very stony clay loam, brown (7.5YR 4/2) dry; moderate medium and fine subangular blocky structure; extremely hard, firm, very sticky and very plastic; many roots; many very fine and fine pores; 20 percent stones, 10 percent cobbles and 10 percent pebbles; neutral (pH 6.6); clear smooth boundary. (19 to 26 inches thick)
Bw3--39 to 60 inches; very dark grayish brown (10YR 3/2) and dark brown (7.5YR 3/2) very stony clay loam, dark brown (7.5YR 3/2) dry; moderate fine and very fine subangular blocky structure; very hard, firm, slightly sticky and slightly plastic; few roots; many very fine and common fine pores; 30 percent stones, 10 percent cobbles, and 10 percent pebbles; slightly acid (pH 6.3).
TYPE LOCATION: Tutuila Island, American Samoa; at Aua 0.8 miles from coast highway on road to Afono; the site is about 200 feet west of the road; lat. 14 degrees 16 minutes 22 seconds S. and long. 170 degrees 39 minutes 20 seconds W.
RANGE IN CHARACTERISTICS: Thickness of the solum is 35 to 60 inches or more. AC horizon is present in some pedons. The profile is 5 to 30 percent stones, 5 to 15 percent cobbles, and 5 to 20 percent gravel, and averages 35 to 50 percent rock fragments between depths of 10 to 40 inches. Reaction is slightly acid or neutral.
The A horizon has hue of 5YR through 10YR, value of 2 or 3 moist, or 3 or 4 dry, and chroma of 2 or 3 moist. The fine earth fraction is silty clay loam, silty clay or clay loam.
The B horizon has hue of 5YR through 10YR, value of 3 or 4, and chroma of 2 or 3 moist or dry. The fine earth fraction commonly is clay loam and ranges to silty clay loam and clay.
COMPETING SERIES: This is the Fagasa series in another family. The Fagasa soils have less than 35 percent rock fragments in the control section and have a paralithic contact at depths of 20 to 40 inches.
GEOGRAPHIC SETTING: Aua soils are on talus slopes. Slopes are 15 to 60 percent. These soils formed in colluvium and alluvium derived from material weathered from basic igneous rock. The mean annual rainfall is 150 to 250 inches, and the mean annual temperature is about 79 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Leafu and the competing Fagasa soils. Leafu soils are on valley floors and have mottles.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Aua soils are used for subsistence farming and homesite. Taro, breadfruit, banana, and coconut are the main crops grown. Areas not cultivated are in tropical forest.
DISTRIBUTION AND EXTENT: Island of Tutuila, Ofu, and Olosega. The soils of this series are of small extent, about 2,400 acres. MLRA 197.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: American Samoa, 1982.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - From the surface to 60 inches. The soil meets the properties for the cummulic subgroup with the exception of soil slope.
Taxonomic Version: Second edition Soil Taxonomy, 1999.
ADDITIONAL DATA: Characterization data are available on the type location, pedon number S81-AQ603-022