#6 Forest Succession Forests are older habitats than fields. One clue that tell us this is the larger size of trees. Use the measuring tape to take the marked Aspen tree’s circumference, or distance around the trunk, in centimeters. Measure at the same height of the pole that the tape hangs from. text field What is the tree's circumference in centimeters? Answer with a number only, for example: 5, 8.2, 9 Link (required) Last modified on Jul. 21st, 2017 at 11:11am by .