Iron Redox Biogeochemistry: Controls on Carbon and Phosphorus Cycling in Humid Tropical Forests

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DEB 0543558W. L. Silver, M. K. Firestone, and G. SpositoIron Redox Biogeochemistry: Controls on Carbon and Phosphorus Cycling in Humid Tropical Forests Carbon plays a central role in global climate change, and the growth, death, and decomposition of biota in humid tropical forests have a large impact on the global carbon cycle. Tropical forests dominantly occur on highly weathered soils rich in iron and low in phosphorus. Phosphorus is considered the nutrient most commonly limiting to net primary productivity in the tropics. Modeling studies, however, suggest that the vegetation uses considerably more phosphorus than is thought to be available in soils. Iron minerals can sequester phosphorus under aerobic conditions, and release it via iron reduction under anaerobic conditions. Iron reduction may also contribute significantly to the release of carbon dioxide, a greenhouse gas, during anaerobic periods. Fluctuating redox conditions are common in these soils, allowing iron to be rapidly regenerated during oxic periods and drive phosphorus and carbon dioxide release during the anoxic phases. The overarching hypothesis of the proposed research is that the redox biogeochemistry and microbiology of iron provide a key to understanding the phosphorus bioavailability paradox and the cycling of phosphorus and carbon in highly weathered soils.This project will train Puerto Rican high school students in field-based scientific research, and help fund summer research apprenticeships as part of the Geballe Research Opportunities for Undergraduates Program. The proposed research will also train two undergraduate students, two graduate students, and two post doctoral scientists.