Research Conducted at Duke Forest FACE (IMAGE) Indiana University Caption The research was conducted at the Duke Forest Free Air Carbon Dioxide Enrichment site in North Carolina, where mature loblolly pine trees were exposed to increased levels of carbon dioxide for 14 years, making it one of the longest-running carbon dioxide enrichment experiments in the world. Credit Will Owens Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.