Oak Rings (image) University of Arizona Share Print E-Mail Caption Charlotte Pearson and her team measured single tree rings of known age from low-altitude oak (pictured) and high-altitude bristlecone pine, and compared those measurements with the internationally agreed radiocarbon calibration curve. Credit © Peter Brewer Usage Restrictions This visual may only be used in conjunction of reporting/posting of this news release. Credit must be stated as indicated. Share Print E-Mail 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.