Burnwood Trail Stop 6: How Tree Age is Determined

An increment borer with an extracted tree ring sample inside an American beech tree.

Thomas Saladyga

Quick Facts

Location:

38.07674, -81.07780

Significance:

Old-Growth Forest Network

Old-Growth Forest Hike Stop 6 - How Tree Age is Determined

The large tree just off the trail to the left with thick-plated, irregular shaped, blocky bark resembling alligator hide is a blackgum. Blackgum is a long-lived, slow growing tree that is highly tolerant of shade, being able to wait in the understory for centuries before a neighboring tree falls and allows for direct sunlight to reach the forest floor. This blackgum is the oldest tree along the trail and has an inner-ring date of 1674, being at least 350 years old.

How are trees accurately dated? The researchers from Concord University who led the Burnwood study used an instrument called an increment borer to extract a straw-sized sample containing the growth rings from the tree. The increment borer has a sharp bit that is twisted into the tree by the user and the wood sample is then extracted from the hollow auger.

While this tree is confirmed to be at least 350 years old, it could be much older. When coring a large tree, if the increment borer is off from the center of the tree by even a couple of inches, decades of growth rings could be missing from the sample, especially on slow growing trees like the blackgum.