A Tower at NSF's Southern Sierra (IMAGE) U.S. National Science Foundation Caption A tower at NSF's Southern Sierra CZO measures the exchange of water and carbon between forest and atmosphere. Credit Roger Bales, UC Merced 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.