LOCATION NAPUU HI

Established Series
RTG-MRK
06/2012

NAPUU SERIES

The Napuu series consists of shallow, well drained soils that formed in basic volcanic ash in `a`a lava. Slopes range from 2 to 70 percent. The mean annual rainfall is about 560 millimeters (22 inches), and the mean annual air temperature is about 20 degrees C (68 degrees F).

TAXONOMIC CLASS: Medial-skeletal, amorphic, isothermic Lithic Haplustands

TYPICAL PEDON: Napuu extremely cobbly highly organic medial sandy loam, on a west facing, slightly convex, 2 percent slope under dryland forest at an elevation of 626 meters (2,055 feet). (Colors are for moist soils unless otherwise noted. All textures are "apparent field textures". pH measured with electrode in 1:1 water. When described on September 20 ,1993, the soil was dry throughout.)

2C1/A1--0 to 15 centimeters (0 to 6 inches); black (10YR 2/1) extremely cobbly highly organic medial sandy loam, dark brown (10YR 3/3) dry; strong very fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine, common medium, and few coarse and very coarse roots; many very fine and fine, and common medium interstitial pores; 70 percent angular `a`a cobbles and 15 percent angular `a`a gravel; moderately acid (pH 5.6); the 2C part of this horizon consists of unconsolidated `a`a lava fragments of variable size; clear irregular boundary. (10 to 20 centimeters {4 to 8 inches} thick)

2C2/A2--15 to 38 centimeters (6 to 15 inches); black (10YR 2/1) extremely cobbly highly organic medial sandy loam, dark brown (10YR 3/3) dry; strong fine granular structure; soft, friable, nonsticky and slightly plastic; many very fine and fine, common medium, and few coarse and very coarse roots; many very fine and fine, and common medium interstitial pores; 50 percent angular `a`a cobbles and 35 percent angular `a`a gravel; slightly acid (pH 6.4); the 2C part of this horizon consists of unconsolidated `a`a lava fragments of variable size; abrupt irregular boundary. (15 to 31 centimeters {6 to 12 inches} thick)

2R--38 centimeters (15 inches); hard, massive `a`a blue rock.

TYPE LOCATION: Island of Hawaii, Hawaii County, Hawaii; from Highway 190, at the entrance of Puu Waawaa Ranch, pedon is located 73 meters (240 feet) north-northeast and 11 meters (35 feet) east-southeast of highway. Puu Anahulu Quadrangle; lat. 19 degrees 48 minutes 32.5 seconds N. and long. 155 degrees 50 minutes 40.5 seconds W. (GPS/PLGR; Old Hawaiian Datum).

RANGE IN CHARACTERISTICS:
Depth to bedrock: 25 to 50 centimeters (10 to 20 inches).
Mean annual soil temperature: 18 to 22 degrees C (65 to 72 degrees F).
Rock fragments: 45 to 85 percent by volume of the pedon and range in size from gravel to stones but are primarily gravel and cobble size lava rocks.
Organic carbon (by weight): 20 to 25 percent of the less than 2.0 mm soil material.

2C/A horizon
Hue: 10YR or neutral.
Value: 2 or 3 moist or dry.
Chroma: 0 to 2 moist or 2 or 3 dry.
Soil reaction: Moderately acid or slightly acid (pH 5.1 to 6.5).

COMPETING SERIES: These are the Keaa and Puuikaaka series. Keaa soils are moist in the control section from October to April. Puuikaaka soils have a lithic contact at 5 to 25 centimeters (2 to 10 inches) and overlie pahoehoe lava.

GEOGRAPHIC SETTING: Napuu soils are on mid elevation, leeward slopes of Hualalai Volcano at elevations from 305 to 1067 meters (1000 to 3500 feet). These soils are on all hillslope components of constructional landscapes consisting of undulating to very steep `a`a flows that are 1,500 to 3,000 years old. Slope gradients range from 2 to 70 percent. The soils formed in basic volcanic ash and weathered lava. The mean annual rainfall ranges from 380 and 760 millimeters (15 to 30 inches), with most of the rainfall occurring from January through July. The mean annual pan evaporation ranges from 1520 to 1780 millimeters (60 to 70 inches). The mean annual air temperature ranges from 17 to 21 degrees C (63 to 70 degrees F). The mean summer soil temperature and the mean winter soil temperature differ by less than 6 degrees C (11 degrees F).

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Akahipuu, Kahaumanu, Nanuku, and Waawaa series, and the competing Puuikaaka series. Akahipuu soils have lithic contact at 50 to 102 centimeters (20 to 40 inches). Kahaumanu and Waawaa soils are medial. Nanuku soils are sandy-skeletal.

DRAINAGE AND PERMEABILITY: Well drained. Runoff is negligible in depressions on gentle slopes and high to very high on steeper slopes. Permeability is very rapid in the soil and very slow in the underlying bedrock.

USE AND VEGETATION: Primarily used for wildlife habitat; some areas are used for grazing. Natural vegetation is ohia lehua (Metrosideros polymorpha), fountaingrass (Pennisetum setaceum), lantana (Lantana camara), and cactus (Opuntia).

DISTRIBUTION AND EXTENT: North Kona District, Island of Hawaii; MLRA 161B. The series is of small extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: Island of Hawaii, Hawaii County, Hawaii 2012. Proposed 1996.

REMARKS: Soil moisture - usually moist, but dry in some or all parts for short intermittent periods totaling 90 or more days during the months from July through January in most years (Ustic moisture regime).

Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from a depth of 0 to 38 centimeters (0 to 15 inches) (2C/A horizons).
Andic soil properties - from the surface to a depth of 38 centimeters (15 inches) (2C/A horizons).
Lithic contact - at a depth of 38 inches (15 inches) (2R horizon).

ADDITIONAL DATA: Napuu NSSL sample S94HI-001-012.

National Cooperative Soil Survey
U.S.A.