Measuring sap flow using sensors (IMAGE) University of Toledo Caption Leticia Sandoval, a graduate student at The University of Toledo working toward a master’s degree in biology, taps into a tree at Ottawa National Wildlife Refuge along Lake Erie in Ohio to measure sap flow using sensors. Credit Daniel Miller, The University of Toledo Usage Restrictions None License Original 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.