Oh Deer: Grad Student Studies Effect of Whitetails on Hemlock

Published in Tech Today
by Marcia Goodrich, senior writer

Nicholas Jensen likes hemlocks. “They’re my favorite tree,” he says, both for their graceful, arching tops and branches and for the shady, uncluttered forest floor they create.

But hemlocks are in trouble, down about 99 percent throughout their regional historic range. So Jensen, a master’s student in forest ecology and management, is studying how one particular animal species might impact the survival of the remaining 1 percent.

In winter, whitetail deer–lots of them–gather (or “yard up”) in groves of hemlock and cedar to escape the deep snow. They do eat hemlock, but they also deposit plenty of scat. Jensen wondered if their presence in high numbers was in effect fertilizing the local ecosystem and changing what types of plants were growing there.

Eastern hemlock thrives in poor soils that most other forest trees can’t abide. If those soils become fertile, Jensen thought, they might be colonized by other trees, like sugar maples, that could displace the hemlocks.

Three years ago, he began his study of 39 hemlock groves in the Lake Superior basin, conducting “pellet counts” and tracking the types of plants growing on the forest floor. Locally, he visited hemlock groves near Point Abbey and Big Eric’s Bridge, in Baraga County.

Hemlock groves let very little light through to ground. Only a few species of low-growing plants, including wild lily of the valley and wood ferns, grow under these conditions. However, Jensen discovered that different species of plants grow in hemlock groves that shelter lots of deer in the winter.

Just why this is happening isn’t clear. Maybe these new plants like the richer soils, maybe the deer are eating saplings and making way for additional low-growing plants.

What is clear is that something is going on, Jensen says. “It’s important to understand this. Hemlocks are an important resource, and they are really under pressure,” he says. “My hope is that we’ll be able to raise awareness of the effect deer may be having, and that our findings will someday be considered in forest management. It could be relevant to the persistence of this forest type.”

Jensen presented his work at the Graduate Student Council Research Colloquium, held April 2-3 at the Rozsa Center. His advisor is Associate Professor Chris Webster (SFRES).