Ecological Site Description Ecological Site Characteristics Site Identification
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FOTG Section II. Natural Resources Information F. Ecological Site Descriptions F159BY500HI – Ohia-Koa/Hapu`u-Kanawao Forest Ecological Site Description Ecological Site CharacteristicsSite Identification
Physiographic Features This ecological site occurs on lava flows on sloping mountainsides of shield volcanoes. Lava flows are `a`a (loose, cobbly) or pahoehoe (smooth, relatively unbroken). Volcanic ash flows range from very shallow to very deep on the underlying lava.
Climatic Features Average annual precipitation ranges from 50 to 140 inches. Most of the precipitation falls from October through March, with November and January being the wettest months. Average annual temperature ranges from 54 to 71 degrees F. The climate generally can be classified as udic and tropical in nature. Climate chart
Influencing Water Features There are no water features influencing this site. Representative Soil Features Typical soils are basic volcanic ash deposited over one of three underlying substrates: `a`a lava, pahoehoe lava, or pumice over volcanic rock. There is also a small area of alluvium deposited over pahoehoe lava (Fluvents, soil map unit 557). One soil map unit (534 Kahaluu-Lava flows complex, 2-10% slopes) formed in highly decomposed organic matter over pahoehoe lava. Most landscape surfaces in this ecological site are 1,500 to 10,000 years old, with a few areas less than 1,000 years old. The Na Manua Haalou area, on the western mauka boundary of Kau Forest Reserve, contains Pu`ali soils exhibiting the wetter range of characteristics of the soil series as evidenced by common to many redoximorphic concentrations. This area receives additional water runoff from surrounding, higher elevation pahoehoe flows. Most soils of this ecological site are moderately well or well drained. Soils of the Ehehuiki series are somewhat poorly drained; Fluvents are somewhat excessively drained. Available water capacity in most soils ranges from three to eleven inches. Soils of the Kaholimo series in the northeast mauka part of Kau Forest Reserve (map unit 573) have available water capacity of two inches, and soils of the Kahaluu series in the southern mauka part of Kau Forest Reserve (map unit 534) have available water capacity of one inch; vegetation in the drier, mauka portions of these map units represent the driest extreme of this ecological site. Available water capacity refers to the volume of water available to plants in the upper 40 inches of soil, including rocks, at field capacity. Permeability is very slow in shallow soils overlying pahoehoe or in soils that have an ironstone pan near the surface. Permeability of most other soils is moderately slow to moderately rapid. Runoff potential ranges from negligible in `a`a to very high over pahoehoe. Moist surface colors range from very dark brown to black. Soil reactions (pH in CaCl2) range from extremely acid to moderately acid in surface horizons and extremely acid to neutral in subsurface horizons. In surface horizons of some soils a pH (in CaCl2) as low as 4.1 may be encountered. Soil temperature regimes are isothermic to isomesic. Soil moisture regimes are udic (soil moisture control section is not dry in any part for as long as 90 cumulative days in normal years).
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