Construction Crane for Carbon Dioxide Signaling (image) University of Basel Share Print E-Mail Caption Artificial signals through labeled carbon dioxide: a construction crane is used to treat the crowns of the spruce trees with gas. Credit University of Basel, research group C. Körner Usage Restrictions Give adequate credit. 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.