The Duke Forest Free-air CO2 Enrichment (FACE) experiment is the longest running experiment in which an intact forest ecosystem is exposed to elevated concentrations of atmospheric CO2. The experiment addresses fundamental questions about how human emissions of CO2 to the atmosphere affect carbon sequestration and nutrient cycling in forests. The soils in the FACE experiment will be sampled and chemically analyzed to better understand how soil nitrogen availability controls carbon sequestration and enhanced tree growth in response to rising CO2 concentration. To date, the experiment has shown that elevated CO2 increased carbon storage in trees and in the forest floor (i.e., the litter layer). However, increases in the carbon content of the mineral soil were not observed. It is likely that the rates of soil carbon sequestration are too slow to be easily detected. Information from further soil chemical analyses will identify the source of the additional nitrogen required to support the observed increase in tree growth.
Understanding nitrogen limitation of tree growth and productivity is vital for predicting the long-term response of forest ecosystems to rising atmospheric CO2 concentrations. Carbon sequestration in forests can potentially mitigate climate change associated with human CO2 emissions. Undergraduate students at Bowdoin College will conduct much of this research during year-long honors projects in biology and chemistry. Additionally the results of this research will be presented in environmental science courses and research seminars to reach a greater number of students.
