Title: Assessing biological vs. physical controls of carbon dioxide flow from soil using Radon-222

(Research Advisor:  Christopher S. Martens, Ph.D., Biology Sponsor:  Joseph J. Kieber, Ph.D., Mentor: Howard P. Mendlovitz, Research Engineer)

Robert L. Shapiro

Global increases in atmospheric carbon dioxide make the question of how forests will respond to these changes increasingly important.  Present research includes how elevated atmospheric CO₂ affects the movement of CO₂ gas out of the soil.  Most researchers, however, are unable to assess to what extent changes in CO₂ flow are due to biological rather than physical processes. The flow of radon-222 gas out of the soil was measured at several sites in the Duke Forest, half with normal atmospheric CO₂ levels and half with artificially elevated CO₂ concentrations in the forest canopy.   Because radon is biologically and chemically inert, its flow is only controlled by the physical processes in and above the soil that also affect CO₂.  Therefore, comparison of the radon movement data with CO₂ movement data allowed differentiation between changes in CO₂ flow due to biological processes and those due solely to physical processes.