 The Forest Atmosphere Carbon Transfer and Storage, or FACE site, is an outdoor research facility located in Duke Forest. For more than 20 years, a multinational, multidisciplinary group of scientists have been studying the effects of carbon dioxide on forests and plants in relation to climate change. When these scientists share their findings, a picture of a wide range of outcomes that result from exposure to high levels of carbon dioxide begins to emerge. At the FACE site, stands of trees are exposed to levels of carbon dioxide that we can expect to experience in the near future. Elevated carbon dioxide warms the Earth's atmosphere, but it is also used by plants during photosynthesis. So you might think of elevated carbon dioxide levels as a sort of fertilizer. In the main experiment on Loblolly Pines, small stands of trees are exposed to elevated levels of carbon dioxide and paired with a control group of trees that is not exposed. The carbon dioxide, stored in a large tank on site, is mixed with air and pumped through a system of PVC pipes surrounding the trees and the test plots. These exposed trees receive exactly 200 parts per million above the natural concentration of carbon dioxide found in their environment. This difference in concentration between the exposed and the unexposed tree stands is closely monitored and adjusted, ensuring the exposed stands always maintain this consistent elevated level of carbon dioxide. The concentration of carbon dioxide in several other important parameters are measured from tall towers above the trees. This allows scientists to get well-mixed samples at different elevations. There is a constant flow of information from the trees, including measurements of atmospheric variables and carbon dioxide levels. Instrument readouts are compiled by a computer on site. Data collection of some of the same parameters also happens via satellite. It is a challenge to compare the satellite data to the data gathered on the ground. Since the trees are not isolated, scientists also study the effects of elevated carbon dioxide on many other related plants, animals and soil factors. At predetermined times, samples of the trees are harvested and a variety of measurements related to the growth and health of the tree are made by examining samples of leaves, bark and other tissues. Information collected from the face site and other sites like it throughout the world help give a more complete picture of what the impact of climate change is likely to be on forests and crops and the potential for these plants to reduce the impact of climate change in the future.