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Emma Sage - Biogeochemistry

Hampshire College, Amherst, MA

Effects of Elevated Carbon Dioxide and Nitrogen Fertilization on Soil
Respiration of a Brackish Marsh

There is substantial evidence that the concentration of carbon dioxide (CO2) and methane (CH4) are increasing in our atmosphere due to anthropogenic factors. Nitrogen is also increasing in our soils and atmosphere due to human deposition and will continue to increase with the human need for resources.  Elevated CO2 and nitrogen directly influences ecosystems by altering plant physiology. How global CO2 and methane budgets will respond to future concentrations of atmospheric CO2 is unknown.  In this study, the respiration of both carbon dioxide and methane from soils was measured at the Biogeochemistry Lab’s new elevated CO2 and nitrogen site, located on a brackish marsh. This site was designed to study belowground processes and the movement of carbon through the ecosystem.  Closed-chamber soil respiration was measured on the twenty new experimental chambers. We hypothesized that the increase of nitrogen and CO2 in the experimental chambers would lead to an increased plant biomass and therefore respiration of greenhouse gases due to increased microbial activity.  For biomass it was found that nitrogen but not elevated carbon dioxide increased productivity, and that there was a positive CO2 by nitrogen interaction. No relevant increase in the respiration of CO2 was found on any sampling dates, possibly due to a dry spring. The respiration of methane was found to be positively correlated with a CO2-nitrogen interaction in chambers with both treatments. These finding suggest that in the future coastal marshes could exacerbate global warming.       
Emma Sage plans to continue this project this fall while finishing her undergraduate degree at Hampshire College (Amherst, MA). She also is excited to begin applying to PhD candidate positions in ecosystem ecology, biogeochemistry, and climate change. Years from now, she aspires to be in a modestly paid job which warrants a minimal amount of stress so she can continue to enjoy her work in science.

Quote: This summer has been full of opportunity. I have gained experience in lab and field techniques.  I have made contacts which will benefit me later in my career. I finally am convinced that my work as a young scientist will influence research and have a positive impact on the world. That is the passion which I brought to science, and that has been realized at the Smithsonian Environmental Research Center.

Funding provided by the National Science Foundation – Research Experience for Undergraduates (REU)