Illinois Natural History Survey - University of Illinois

The Naturalist's Apprentice: Big Trees!


 to discover some of Illinois' largest trees


Materials: multiple copies of Big Trees!


Vocabulary: circumference, diameter at breast height (dbh)


Comments: When most individuals think of big trees, the giant redwoods or sequoias of California are the first to come to mind. Illinois, however, has its share of large trees, and this addition of The Naturalist's Apprentice will have students calculate just how big some of these giants really are. Foresters and other individuals interested in knowing tree size usually use a measurement called diameter at breast height, or dbh. This measurement is usually taken about 52 inches from the ground surface. Currently, Illinois' largest tree is a bald cypress in the Cache River lowlands of southern Illinois.


1. Give each student a copy of the handout Big Trees! They must use the information found there to calculate the dbh of the trees given.

2. The correct formula for calculating dbh from the circumference is D = C/(pi) where D = diameter, C = circumference, pi = 3.14.


Use the information given below to calculate the diameter of some of Illinois' largest trees. You should use the formula C = (pi)D for your calculations. (Hint: you must rearrange the formula to find D.)


Michael Jeffords, Center for Economic Entomology.

Charlie Warwick, editor

Illinois Natural History Survey

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Champaign, IL 61820

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