Slide show: The Tree Doctor

Bruce Allison, right, an adjunct professor in the forest and wildlife ecology department, teaches students how to assess the stability of trees using modern, non-destructive techniques. Here Allison performs an acoustic tomography scan of the President’s Burr Oak, a 300-year-old tree located atop Observatory Hill. The scan, which involves measuring the speed of sound waves as they pass through the trunk, helps arborists locate internal defects in trees. Also pictured, left to right, are Ph.D. candidate Shan Gao, undergraduate Joelle Baird and Ph.D. candidate Li Li.

Photos: Bryce Richter | Words: Nicole Miller