Interactions between Rainfall, Nutrient Cycles and Decomposition in Lowland Tropical Rainforests

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Tropical rain forests exchange more carbon dioxide and water with the atmosphere than any other terrestrial biome, and thus play a major role in climate regulation. Wetter portions of the tropical biome store large amounts of carbon in tree biomass and soils, but those reserves - especially soil carbon - may be sensitive to predicted changes in rainfall. Thus, this project will manipulate the amount of rainfall that reaches soils in a wet Costa Rican rainforest, and test how such changes alter leaf litter and soil carbon decomposition, and the amount of CO2 that is released from the soil surface to the atmosphere. In addition, it will test how nitrogen and phosphorus availability, key nutrients that also vary greatly across the tropical biome, affect the responses to rainfall manipulation. Taken as a whole, the experiments will demonstrate how changes in rainfall in wet tropical forests may affect ecosystem processes that have direct relevance to earth's climate, with a focus on soil carbon storage. The data produced here will improve understanding of how this large soil carbon reservoir may respond to a changing climate, and thus how it might moderate or augment continued climate change. Finally, the project will provide training and education to young scientists in the U.S. and Costa Rica, and will develop an outreach program for Colorado school children.