Changing Forests in a Changing Climate

If beech trees could read, they might wonder what the heck they ever did to deserve the recent headlines decrying their growth. “Beech trees take over northeastern U.S. and it’s not a good thing”; “Beech trees booming as climate changes, and that’s bad for forests”; “Beech trees in the U.S are delivering a scary message about climate change”—all these headlines and more have led off stories summarizing a new study about changing forest composition that was published recently.

Can’t a dominant wildlife-friendly tree species get a hug around here?

The report, entitled “A three-decade assessment of climate-associated changes in the forest composition across the northeastern USA” by Aaron Weiskittel of the University of Maine and Robert Wagner of Purdue, was published in the Journal of Applied Ecology. Using U.S. Forest Service data, they found that from 1983-2014 that beech became more abundant as sugar maple, red maple and birch decreased.

Less sugar maple? Sweet ever-lovin’ pancakes and waffles, this can’t be good news, right?

As the title of the report indicates, the authors attribute this trend to climate change, specifically to warmer temperatures and more moisture.

I asked several of our (Forest Society) foresters about the situation. “We know we have a beech issue out there,” said Managing Forester Wendy Weisiger. “Foresters have been talking about this for years but not always specifically related to climate change.”

So why is it a “beech issue”? Why is beech the Rodney Dangerfield of the forest?

Well, as the report authors point out, “This would be a significant management concern as beech is associated with a widespread bark disease, is commercially less desirable, and can limit natural regeneration from other species.”

Or in other words, if you’re a forestland owner managing for timber value, maple and birch are far more valuable than beech. And beech has a tendency to win out over other species fighting for space in the forest. Beech also tends not to be as tasty to deer and moose who browse on the maple and birch instead.

“Beech does very well under shaded or partially shaded overstory stands because of its ability to tolerate shade,” explained Steve Junkin, field forester at the Forest Society. “Northern hardwood stands that are thinned often reproduce beech above other desired species unless it’s a really good site high in calcium.”

OK, fine, beech trees are guilty of hogging the forest. So if a landowner wants to manage for sugar maple or birch, what might we do?

“People have tried many methods to reduce beech competition like cutting it higher, burning it, and even not cutting it or girdling it,” Weisiger said.

The report authors note that the changes they detected over the last 30 years “may continue if higher intensity harvesting and disturbances (i.e. large-scale canopy openings) do not occur. Our results emphasize the need for management strategies such as higher intensity harvesting methods, vegetation control and limiting browsing pressure to reduce beech dominance.”

What we’re talking about is using larger silvicultural clearcuts to abate the spread of beech.

“Clearcuts encourage birch and pin cherry trees that otherwise have a hard time growing in shaded environments,” Junkin said. “As these clearcuts age they develop an understory of more desirable commercial species such as sugar maple and yellow birch which can actually be trained by the shorter living birch and pin cherry that can consequently produce more valuable sawtimber through lower bole branch shedding.”

Or, as Field Forester Gabe Roxby explained, “Big openings, lots of light, and you get species that can take best advantage of that environment and grow quickly.  Small openings, lots of shade, and you get species that can handle those challenging conditions.”

But Junkin also noted that “It shouldn’t be a goal in every situation to limit beech trees as they do represent an important food source for wildlife and can develop into late successional forests which is important to have at least a portion of our forests in this forest type again for wildlife and ecological diversity.”

Weisiger concurs: “Steve is right in that we do like beech and favor it in places, particularly where it’s more resistant to the blight (an exotic disease that originally spread rapidly in the south due to firewood movement). The Forest Society just harvested in Lempster to favor nut-producing beech for habitat.  However, it’s not good when our sugar maple and oak stands convert to beech-dominant and we lose species diversity.”

Beech is known as a good wildlife tree because of beech nuts, which are an important food source for squirrels and chipmunks (who are an important food source themselves), as well as black bears, raccoons, deer, porcupines and foxes. Before the Passenger Pigeon became extinct, they fed on beech nuts and roosted in the branches of beech trees. (Go back much further, prior to the Pleistocene Ice Age, and beech trees are thought to have been even more widespread across North America than they are today.)

And while beech may not have high timber value, humans do use it. Slats of beech wood are spread around the bottom of fermentation tanks for Budweiser beer. Beech is great for firewood. Who doesn’t like beer around a bonfire?

But we like our more valuable sawtimber (and maple syrup), too, and so our headlines decry the spread of beech.

Jack Savage is the executive editor of Forest Notes, the quarterly magazine of the Society for the Protection of New Hampshire Forests. He can be reached at jsavage@forestsociety.org.