LOCATION OHIA HI

Established Series
Rev. RCH/HHS/NEM/AMS
06/2012

OHIA SERIES

The Ohia series consists of deep, well drained soils that formed in material weathered from volcanic ash which overlies pahoehoe or `a`a lava on the lower windward slopes of Mauna Loa Volcano. Slopes range from 3 to 10 percent. The mean annual rainfall is about 4,064 millimeters (160 inches) and the mean annual air temperature is about 19 degrees C (66 degrees F).

TAXONOMIC CLASS: Hydrous, ferrihydritic, isothermic Acrudoxic Hydrudands

TYPICAL PEDON: Ohia hydrous silty clay loam under pasture on a 5 percent slope at an elevation of 603 meters (1980 feet). (All textures are "apparent field textures" and colors are for moist soil unless otherwise noted.)

Ap1--0 to 15 centimeters (0 to 6 inches); dark brown (7.5YR 3/2) hydrous silty clay loam; moderate medium and very fine subangular blocky structure; friable, slightly sticky, moderately plastic; weakly smeary; roots matted; many medium and fine pores; extremely acid (pH 4.1); clear wavy boundary.

Ap2--15 to 23 centimeters (6 to 9 inches); dark brown (7.5YR 3/2) hydrous silty clay loam; common fine distinct dark reddish brown (5YR 3/4) mottles; moderate fine and very fine subangular blocky structure; friable, slightly sticky, moderately plastic; weakly smeary; many roots; many very fine and fine pores; extremely acid (pH 4.3); abrupt wavy boundary. (Combined thickness of the Ap horizon is 18 to 25 centimeters {7 to 10 inches} thick).

Bw1--23 to 33 centimeters (9 to 13 inches); dark reddish brown (5YR 3/3) hydrous silty clay loam; weak fine subangular blocky structure; friable, slightly sticky, moderately plastic; strongly smeary; many roots; many very fine to coarse pores; strongly acid (pH 5.1); abrupt wavy boundary.

Bw2--33 to 58 centimeters (13 to 23 inches); dark reddish brown (5YR 3/3) hydrous silty clay loam; moderate fine and very fine subangular blocky structure; friable, moderately sticky, moderately plastic; strongly smeary; common roots; common very fine pores; moderately acid (pH 5.7); abrupt wavy boundary.

Bw3--58 to 81 centimeters (23 to 32 inches); dark reddish brown (5YR 3/4) hydrous silty clay loam; moderate fine and very fine subangular blocky structure; friable, moderately sticky, moderately plastic; strongly smeary; common roots; common fine and very fine pores; moderately acid (pH 6.0); clear wavy boundary.

Bw4--81 to 157 centimeters (32 to 62 inches); dark brown (7.5YR 3/2) hydrous silty clay loam; moderate fine and very fine subangular blocky structure; firm, slightly sticky, moderately plastic; strongly smeary; few roots; common very fine pores; common firm and very firm volcanic ash fragments; moderately acid (pH 6.0); abrupt smooth boundary. (Combined thickness of the Bw horizons is 75 to over 135 centimeters {30 to over 53 inches} thick).

2R--157 centimeters (62 inches); hard, massive pahoehoe lava.

TYPE LOCATION: Island of Hawaii. From Mountain View village, take Kiyabu Camp Road northwest for approximately 1/4 mile. Park on right side of road next to newspaper mailbox and Private Property sign. Follow fenceline at roughly 60 degree bearing until corner post is reached. From corner post head north for approximately 400 yards towards large albezia tree. Pit is just to the right of the tree, marked with red flagging. Mountain View Quadrangle; 19 degrees 33 minutes 34.6 seconds North latitude and 155 degrees 6 minutes 39.3 seconds West longitude. (Old Hawaiian Datum).

RANGE IN CHARACTERISTICS:
Depth to bedrock: 102 to over 152 centimeters (40 to over 60 inches).
Rock Fragments: 0 to 30 percent total volume for the soil, typically mostly cobbles concentrated in the lower horizons of the profile. Some pedons contain thin bands of highly weathered weakly cemented volcanic ash at depths of 51 to 127 centimeters (20 to 50 inches).
Soil Reaction: Extremely acid to slightly acid.
Mean annual rainfall: 3,500 to 4,500 millimeters (137 to 177 inches).
Mean annual soil temperature: 16 to 22 degrees C (61 to 72 degrees F).

A Horizon
Hue: 7.5YR to 10YR.
Value: 2 or 3 moist.
Chroma: 2 or 3 moist.
Texture: Medial or hydrous silt loam or silty clay loam.
Smeariness: Weakly or moderately smeary.
Soil Reaction: Extremely acid to moderately acid (pH 4.0 to 5.6).
Mottles: May or may not be present.

Bw Horizons
Hue: 2.5YR to 7.5YR.
Value: 3 or 4 moist.
Chroma: 2 to 4 moist.
Texture of the fine earth: Hydrous silt loam, silty clay loam, or loam.
Smeariness: Moderately or strongly smeary.
Soil Reaction: Strongly acid to slightly acid (pH 5.1 to 6.5).
Rock Fragments: 0 to 65 percent occur at some locations at depths below 60 centimeters (24 inches).

COMPETING SERIES: These are the Akaka, Honokaa, Honomanu, Kaiwiki, Kehena, and Maile series. Akaka soils are greater than 100 centimeters (40 inches) deep and have a mean annual soil temperature of 15 degrees C (59 degrees F). Honokaa soils contain discrete layers of buried ash in the lower portion of the profile. Honomanu soils are less than 125 centimeters (50 inches) deep and contain silty clay textured subsurface horizons. Kaiwiki soils are greater than 183 centimeters (72 inches) deep and have a mean annual soil temperature of 22 degrees C (71 degrees F). Kehena soils are moderately deep, with depths to bedrock ranging from 50 to 90 centimeters (20 to 35 inches). Maile soils have an udic soil moisture regime.

GEOGRAPHIC SETTING: The Ohia soils are on the lower windward slopes of Mauna Loa Volcano at elevations of 366 to 914 meters (1,200 to 3,000 feet). The soils are located on both `a`a and pahoehoe lava flows 5,000 to over 10,000 years old. Slopes range from 3 to 10 percent. The soils formed in basic volcanic ash over either `a`a or pahoehoe lava. Mean annual rainfall ranges from 3,500 to 4,500 millimeters (137 to 177 inches), and cloud cover is common. The mean annual pan evaporation ranges from 1,016 to 1,270 millimeters (40 to 50 inches). The mean annual soil temperature ranges from 16 to 22 degrees C (61 to 72 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 Akihi, Hao, Hilea, Ihope, Keei, Kiloa, and Puhimau series. Akihi soils are skeletal. Hao soils contain a placic horizon. Hilea and Puhimau soils have a lithic contact at 5 to 50 centimeters (2 to 20 inches). Ihope soils have a lithic contact at 5 to 50 centimeters (2 to 20 inches) and are somewhat poorly drained. Keei and Kiloa soils are primarily composed of organic soil material.

DRAINAGE AND PERMEABILITY: Well drained. Runoff is moderate. Permeability is moderately slow in the soil and very slow in the underlying bedrock.

USE AND VEGETATION: These soils are used for forestland, livestock grazing, wildlife habitat, and orchard crops. Natural vegetation is strawberry guava (Psidium cattleianum), guava (Psidium guajava), hapuu treefern (Cibotium glaucum), and uluhe fern (Dicranopteris linearis).

DISTRIBUTION AND EXTENT: Puna District of the island of Hawaii. This series is moderately extensive, with a total of about 15,000 acres. MLRA 159A.

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

SERIES ESTABLISHED: Soil Survey, Territory of Hawaii, 1949.

REMARKS:
03/08: Updated acres mapped. AMS.
OSD revised 09/03 for the update of the Island of Hawaii soil survey.

Diagnostic horizons and features recognized in this pedon are:

Perudic Moisture Regime
Isothermic Temperature Regime
Andic soil properties- 0 to 157 centimeters (0 to 62 inches) (Ap1, Ap2, Bw1-Bw4 horizons).
Umbric epipedon- 0 to 58 centimeters (0 to 23 inches) (Ap1, Ap2, Bw1 and Bw2 horizons).
Cambic horizon- 58 to 157 centimeters (23 to 62 inches) (Bw3 and Bw4 horizons).
Lithic contact- 157 centimeters (62 inches) (2R horizon).

National Cooperative Soil Survey
U.S.A.