PARENT SESSION
Poster Session #26: Soil Ecology I.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
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Arboreal organic soils 50 m above the forest floor in coast redwood canopies.
ALLEN, HEATHER*,1, GRAHAM, ROBERT1, SILLETT, Stephen2, 1 UNIVERSITY OF CALIFORNIA, RIVERSIDE, Riverside, CA2 HUMBOLT STATE UNIVERSITY, Arcata, CA
ABSTRACT- Within the canopies of old-growth coast redwood (Sequoia sempervirens), soils up to 1.8 m deep have formed in crotches and on massive branches, 50 m above the forest floor. These soils are important habitats for desiccation sensitive organisms in the forest canopy ecosystem. We have described and sampled two of these arboreal soils in order to investigate how they form and behave. The primary vascular epiphyte growing in canopy is leather leaf fern (Polypodium scouleri). Fern biomass and redwood leaves and bark appear to be the main parent material of the soils, which are apparently entirely organic. The soils have distinct horizons and soil structure, and meet the classification requirements of Histosols. The soils become more decomposed with depth as fiberous soil components give way to sapric materials. Average plant available water capacity for the profiles is 0.06-0.08 cm3/cm3; the soils have a low bulk density (0.07-0.16 g/cm3) and lose most water at relatively high matric potentials. The C:N ratios are high (38-59 for the <2 mm fraction) throughout the profiles. The soils are ultra acidic, with pH values around 3.0 in 0.01 M CaC12. Decomposition may be hindered by the low pH and low nitrogen content of the soil. These systems are strongly leached, which further limits nutrient availability. This canopy soil research offers a unique ability to look at soil behavior in a system lacking inputs from mineral substrate.
KEY WORDS: organic soils, soil formation, Sequoia sempervirens