Recent guide gives forest owners advice on global warming

If the world is experiencing global warming, how will forests be affected and how should their owners react?

That's the question that the Northern Institute of Applied Climate Science attempted to answer in 2019 when it published a “Climate Change Field Guide for Northern Wisconsin Forests.”

(See the link for more about NIACS, which is “a collaborative effort among the Forest Service, universities, conservation organizations, and forest industry to provide information on managing forests for climate change adaptation and enhanced carbon sequestration”.)

The guide lists a variety of likely effects of global warming, some positive and a number negative.

For instance, the guide predicts that warming would lead to longer growing seasons, but more likely also to frost damage as trees bud earlier.

At the same time, global warming is expected to lead to more "intense” rainstorms, according to the guide, which would cause erosion and may disrupt forest management.

The guide also projects more frequent wildfires and more widespread invasive species growth.

The effects vary by tree species, with some species being affected in a positive way and others experiencing heightened vulnerability.

Two examples of these differing effects are what could happen to quaking aspen and white oak.

Oak is “limited by cold temperatures and growing season frost,” according to the guide. It is “tolerant of drought and (has) episodic, unpredictable nutrient availability”. So it is possible that oak forests could increase their cover in northern Wisconsin, or might not be affected negatively.

In contrast, quaking aspen and paper birch have “upper temperature or drought limits based on their physiology”, the guide says. Quaking aspen and paper birch are near the southern boundary of their habitat so warmer temperatures could cause a shift in their territory.

The impacts on each species is complex so the 92-page guide offers a picture of that complexity for a variety of major species. It provides tree species projections on aspen, birch, jack pine, lowland conifer, lowland hardwoods, oak, red pine, upland spruce and fir, and white pine.

Jason Holmes, Bayfield County forester, described suggested some paths for landowners at the County Forests Association meeting on September 27. He said that encouraging adaptation by maintaining a diverse portfolio of ages and species in a forest makes sense.

“Leave species in the best places for them,” Holmes said.

He also recommended paying close attention to quaking aspen during their regeneration phase.

More information regarding the guide can be obtained online at https://www.climatehubs.usda.gov/hubs/northern-forests. The contact for the guide is Stephen Handler, sdhandler@fs.fed.us for those who may want additional information.