Posted: December 21, 2016

Like the lines etched into the skin of a centenarian, the rings displayed within a cross-section of a tree limb divulge hidden stories, stories of turmoil and stability, life and death.

Oak tree

In October 2015, a limb fell from a large white oak tree located in a field near the Hartley Wood in The Arboretum at Penn State. Kim Steiner, professor of forest biology and director of the Arboretum, jumped at the opportunity to dissect the limb and decipher its messages.

What he learned is that the tree is more than 200 years old; it likely was standing when President George Washington delivered the first "State of the Union Address" in 1790 and when Benjamin Franklin died a few months later.

According to Steiner, the oak tree was struggling in the late 1830s, but began to grow faster in 1846. "Very possibly that is when the field in which the oak sits was cleared of most trees, which made it possible for the oak to grow more rapidly," he said.

Another period of slow growth for the tree began in 1962 and lasted for 10 years. "Mild to severe droughts occurred in these years," said Steiner. The tree also grew slowly for a number of years beginning in 1981, the year that the gypsy moth arrived in central Pennsylvania. "Nearly every oak tree in the valley was defoliated that year, and many oaks died," said Steiner.

Steiner's tree ring analysis on the white oak limb adds richness to the story of the nearby Hartley Wood. "A fellow named Hartley purchased the property in the 1780s," Steiner said. "While the surrounding land was clear cut to fuel the Centre Furnace, Hartley maintained this wood lot. We're not sure why, but we're glad he did."

--Sara LaJeunesse