A tagged subalpine fir tree (IMAGE) University of Colorado at Boulder Caption A tagged subalpine fir tree, one of more than 5,000 marked trees monitored as part of this 37-year-long study in the Colorado subalpine forest on Niwot Ridge, west of Boulder. Credit Robert Andrus 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.