Proposed soil classification of the island of Oahu, Hawaiian Islands
1931
Dunnewald, T.J.
1. The podsol process, which is essentially leaching by organic matter, occurs wherever tree growth covers soil or wherever organic matter is deposited on top of the soil even in tropical climates. 2. Lateritic soils become podsolized when covered with trees. The podsolic process is slower or weaker at 20 to 30 inches of rainfall, more rapid at 100 inches, and most active at 400 inches. 3. The lateritic process is due largely to high temperature but reaches a maximum where high temperature and rainfall are combined. The quartz grains first become coated with reddish iron and then by black organic matter. The advanced stages of laterization seem to be marked by a greater number of coated grains rather than by any increased thickness of the coatings. 4. The SiO2 sesqui-oxides ratio of laterites becomes, narrowest under combined high rainfall and high temperature. The ratio is larger under arid conditions and under high rainfall combined with cooler temperatures. 5. Silica is retained less largely in the high lime-basic-arid laterites, and more so in the most acid, timbered, and most humid laterites of the higher elevations. The sesqui-oxides are lowest where the silica is highest, and vice versa. 6. No hard pan of iron salts is indicated in these soils except a slight tendency in the B horizon of the Fern Forest soil.
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