Dissimilatory and Assimilatory Controls on Nitrogen Retention and Loss: Oxygen and Nitrate Dynamics in Tropical Forest Soils

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Abstract00-89783SilverDissimilatory and assimilatory controls on nitrogen retention and loss: Oxygen and nitrate dynamics in tropical forest soilsIn humid tropical forests, the combination of abundant rainfall, soils with high water-holding capacity, and high metabolic activity can lead to conditions where oxygen is rapidly and completely consumed in the soil. These conditions also increase the potential for nitrogen trace gas loss and leaching. In a global context, tropical forests currently have the highest N2O emissions, and can exhibit large nitrogen losses to groundwater relative to temperate forests. Despite this high potential for nitrogen loss, tropical forest plant productivity is not generally nitrogen limited. Dr. Silver and colleagues propose to combine field and laboratory experiments to study nitrogen retention (via dissimilatory nitrate reduction to ammonium, and plant and microbial uptake) and nitrogen loss (via leaching and denitrification) in forests of Puerto Rico. This research will contribute to our understanding of the mechanisms controlling nitrogen dynamics in humid tropical forests, and improve our ability to predict the effects of anthropogenic nitrogen deposition and global change on nitrogen cycling