Science in the Triangle

Higher concentrations of carbon dioxide are pumped into four of the experimental rings. Photo: Will Owen

Late in 2010, an epic ecological experiment in the Triangle will begin drawing to a close when carbon dioxide stops pumping from four massive rings of towers in the Duke Forest. Since 1996, more than 250 scientists at Duke and dozens of other institutions have measured the response of this forest ecosystem to the elevated amounts of carbon dioxide expected in the Earth’s atmosphere in the future. They’ve measured tree and plant growth, photosynthesis, leaf size, soil composition, root growth, and water use in the plots bathed in elevated carbon dioxide and in three other “ambient” control plots.

The first, prototype ring was built in 1994; six more came in 1996 (three controls and three experiments). Each ring consists of 16 metal towers in a 30-meter diameter. Computer-controlled instruments in the experimental rings bathe the interior of the plot in carbon dioxide. It’s called Free-Air CO2 Enrichment, or FACE. As opposed to “chamber studies,” in which plants are studied in carefully controlled growth chambers or greenhouses, the rings are open to nature. That means that mammals and insects can circulate freely and that natural events like hurricanes, ice storms, and droughts affect the research site. Read more…