LOCATION HAKUMA                  HI

Established Series


The Hakuma series consists of shallow, moderately well drained soils formed in basic volcanic ash over pahoehoe lava. Hakuma soils are on the low elevation, windward slopes of Mauna Loa and Kilauea volcanoes. Slopes range from 2 to 10 percent. Mean annual rainfall is about 3,900 millimeters (154 inches) and mean annual temperature is about 23 degrees C (73 degrees F).

TAXONOMIC CLASS: Hydrous, ferrihydritic, isohyperthermic Lithic Hydrudands

TYPICAL PEDON: Hakuma highly organic hydrous loam on a northeast-facing, slightly concave, 2 percent slope in lowland forest at an elevation of 185 meters (610 feet). (Colors are for moist soils unless otherwise noted. All textures are "apparent field textures". pH measured using an Oakton microprocessor based pH meter. When described on July 27, 2005, the soil was moist throughout the profile.)

A--0 to 20 centimeters (0 to 8 inches); very dark brown (7.5YR 2.5/2), highly organic hydrous loam, black (7.5YR 2.5/1) dry; moderate fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine, common fine, and few medium roots throughout; few very fine pores throughout; moderately smeary; moderately acid (pH 5.7); abrupt smooth boundary. (7 to 25 centimeters {3 to 10 inches} thick)

Bw--20 to 31 centimeters (8 to 12 inches); very dark brown (7.5YR 2.5/3), hydrous loam, very dark brown (7.5YR 2.5/2) dry; moderate fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common fine roots throughout; few very fine tubular pores throughout; moderately smeary; 3 percent angular gravel sized volcanic glass and 5 percent subangular cobbles; strongly acid (pH 5.4); abrupt smooth boundary. (0 to 23 centimeters {0 to 9 inches} thick)

2R--31 centimeters (12 inches); hard, massive pahoehoe lava.

TYPE LOCATION: Island of Hawaii; From the village of Keaau, follow Highway 132 southeast approximately 3.5 miles to Pohaku Street. Turn right, southwest, and proceed approximately 2 miles to 40th Street. Proceed through the intersection approximately 150 feet and park. Walk approximately 100 feet north to type location at Mountain View Quadrangle; 19 degrees, 34 minutes, 8 seconds North latitude and 155 degrees, 2 minutes, 2.1 seconds West longitude (Old Hawaiian Datum, 12 feet; measured by Garmin GPS).

Soil moisture: The soil is typically moist throughout the profile. Precipitation exceeds evapotranspiration in all months of normal years (perudic soil moisture regime).
Soil temperature: 22 C (72 degrees F) or higher.
Rock fragments: 0 to 30 percent by volume of the pedon and range in size from gravel to cobble size lava rocks.
Depth to bedrock: 7 to 50 centimeters (3 to 20 inches).
Reaction: Very strongly acid to slightly acid (5.0 to 6.5).

Oa or Oi horizon (when present)
Hue: 5YR to 10YR.
Value: 1 to 3 moist.
Chroma: 1 to 3 moist.
Texture: Highly decomposed plant material or peat.

A horizon
Hue: 5YR to 10YR.
Value: 2 to 3 moist.
Chroma: 1 to 3 moist.
Texture: Hydrous silt loam, hydrous loam. May be highly organic, gravelly, or cobbly.

Bw horizon
Hue: 7.5YR or 10YR.
Value: 2 to 3 moist.
Chroma: 1 to 2 moist.
Texture: Hydrous sandy loam, silt loam or loam. May be cobbly.

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: Hakuma soils are at elevations ranging from 0 to 366 meters (0 to 1,200 feet) on the low windward slopes of Mauna Loa and Kilauea volcanoes. The soils are on all hillslope positions of constructional landscapes consisting of undulating to hilly pahoehoe lava flows that are 200 to 2,000 years old. Slope gradients range from 2 to 10 percent. The soils formed in basic volcanic ash over pahoehoe lava. Mean annual rainfall is 3,000 to 5,000 millimeters (120 to 200 inches) with most of the rainfall occurring from October through April. The mean annual pan evaporation ranges from 762 to 1,016 millimeters (30 to 40 inches). The mean annual air temperature ranges from 21 to 25 degrees C (70 to 77 degrees F). The mean annual soil temperature is 22 degrees C or higher (71 degrees F).

GEOGRAPHICALLY ASSOCIATED SOILS: These are Ohia, Keaukaha, and Olaa soils. Ohia soils are deep and very deep. Keaukaha soils are organic. Olaa soils are moderately deep and skeletal.

DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is high. Permeability is moderately rapid in the soil and very slow in the underlying bedrock.

USE AND VEGETATION: Most of these soils are in open canopied forest. A few areas are used for pasture. Natural vegetation is ohia lehua (Metrosideros polymorpha), treefern (Cibotium chamissoi or C. glauca), uluhe (Dicranopteris linearis) and guava (Psidium guajava).

DISTRIBUTION AND EXTENT: Puna district, Island of Hawaii. These soils are moderately extensive with approximately 13,000 acres. MLRA 162 - Humid and Very Humid Organic Soils on Lava Flows.


SERIES ESTABLISHED: Island of Hawaii, 2012. Proposed in 2005.

Last revised by the state in 08/09 by AMS.
Diagnostic horizons and features (9th edition Keys to Soil Taxonomy) recognized in this pedon are:
Umbric epipedon - from 0 to 25 centimeters (0 to 10 inches) (A and Bw horizons).
Cambic horizon - 25 to 31 centimeters (10 to 12 inches) (Bw horizon).
Lithic contact - at 31 centimeters (12 inches).
Andic soil properties - from 0 to 31 centimeters (0 to 12 inches).
Isohyperthermic soil temperature regime.
Perudic soil moisture regime.


National Cooperative Soil Survey