Close-up of Core from Tree (image) University of Arizona Caption A core extracted from a living Douglas-fir tree in the Santa Rita Mountains south of Tucson, Ariz. Scientists use such cores to study the annual rings of trees, visible on the core as banding. Collecting such cores causes only temporary injury to the tree. Credit Copyright 2009 Daniel Griffin Usage Restrictions This photo may be used only to illustrate a story about the research described in the accompanying release, Hot with Decades of Drought: Expectations for the Southwest. 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.