Document: PET-3-60-9

Erosion and the regeneration of nutrient supply on an old tropical landscape.

VITOUSEK, P.M.* ¹, O.A.CHADWICK ², L.DERRY ³, P.A.MATSON ¹, E.MECKING ¹ and V.M.MONASTRA ³

Stanford University, Stanford, CA 94305 USA ¹
University of California, Santa Barbara, CA 93106 USA ²
Cornell University, Ithaca, NY 14853 ³

Abstract:
Stable constructional surfaces of shield volcanoes become increasingly depleted in rock-derived nutrients over 4 million years of ecosystem development in the Hawaiian Islands. At the same time, fluvial erosion reduces constructional surfaces to a progressively smaller fraction of the landscape. Does this erosion expose little-weathered rocks, and thereby rejuvenate the supply of rock-derived nutrients on slopes? We evaluated soil characteristics and foliar nutrients across erosional slopes and shield surfaces on the oldest Hawaiian island, Kauai. Isotopic analyses demonstrated that 5-8% of the Sr in plants on a shield surface - and 13-31% of the Sr on a slope - was derived from the underlying rock. Foliar P in the dominant tree species averaged 0.06% on shield surfaces, versus 0.081% on slopes. The matrix of nutrient-depleted shield surfaces, rejuvenated slopes, and mixed depositional areas increases the biogeochemical diversity of landscapes on the oldest island, where species diversity also is highest.

Keywords: nutrient availability, weathering, strontium, erosion

This abstract is being presented at: 1:00 PM in session:
Oral Session #13: N Fixation and Biochemical Patterns.