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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

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Old-growth characteristics include large fallen logs and limbs, and large snags and cavity trees. © JMAR Foto-Werks
Old-growth characteristics include large fallen logs and limbs, and large snags and cavity trees. © JMAR Foto-Werks

October 2004

Next steps

Managed old-growth.

Karl Martin, Natasha Kassulke and Tony Rinaldi

The future of old-growth in Wisconsin

The Argonne Experimental Forest located within the Chequamegon-Nicolet National Forest near Three Lakes is no stranger to studies. Since 1947, the Argonne Experimental Forest has been managed as a living laboratory to study methods for managing northern hardwoods. An interpretive trail passes through study areas where you can learn about different cutting methods and their effects.


But now the Wisconsin Department of Natural Resources and its partners are initiating the second phase of the old-growth study and the Argonne is one of several sites for these experiments.

This study differs from earlier studies in that it is long-term, more intensive and compares the results of treating even-aged northern hardwood forests to unmanaged stands.

"The Argonne area was picked because it has been used for research and has extensive areas of unmanaged second-growth forest," says Terry Strong, a research forester with the North Central Research Station. "The study also requires a fairly large acreage, which exists here."

The goal of this silvicultural work is to mimic some of what nature does in the process of creating old-growth, to document ecosystem responses, and to identify economic and social costs and benefits. Other study sites include areas of the Flambeau River State Forest and Northern Highland-American Legion State Forest.

The research has two parts; one concentrating on the role of coarse woody debris and canopy openings, and the other on assessing the use of silvicultural techniques to develop selected old-growth characteristics.

The coarse woody debris study will examine the effects of the debris on carbon and nitrogen cycling, and on insects, microbial composition, vegetation and lichen community structure. Treatments will vary from a control to sits where all the downed wood is removed, to sites where large wood is actually brought in.

To increase species diversity, gaps will be created near ash, oak, yellow birch and hemlock to provide quality habitat and an adequate seed source for regeneration.

There are many questions this study hopes to answer: What are the differences between hardwood and hemlock log decomposition and nutrient cycling? Is the amount of CO2 from the decaying wood significant as compared to the total produced in a forest? Will the number and kinds of insects vary depending on the amount and kind of coarse woody debris? What about changes in the microbial community? What will be the effects on groundlayer vegetation?

"On the Argonne we are mimicking what happens in a windstorm," Strong says. "Once we get enough 20- to 24-inch trees we can cut those to create a gap. We also look for areas with five to six small diameter trees that might have diseases and take all of those out to create an opening in the canopy."

The other part of the second phase of old-growth research deals with silvicultural techniques. The research aims to determine if the forest can accelerate development of old-growth characteristics by creating gaps in the forest canopy and increasing the amount of standing and downed wood. The experiment involves manipulating stand structure through timber harvests. There will be six silvicultural treatments plus a control applied to 60 to 80-year-old northern hardwoods. There will be various combinations of single tree selection, canopy gap creation, snag retention and felled log retention. The specific objectives involve silviculture, economics, wildlife, education and outreach.

Foremost will be comparing and quantifying which management techniques are most effective in creating old-growth forest characteristics. This includes monitoring how quickly trees regenerate and which plant species grow over time. Decay rates, fall rates and build up of coarse woody debris will be examined. Overall growth and timber yields from the treatments will be measured. The costs of the overall silvicultural practices will be assessed , along with costs to develop specific old-growth attributes. In addition, researchers will quantify how these options for managing forests affect regional timber supply and revenues.

Sampling before and after treatments will assess relative abundance of small mammals, amphibians and birds. The association between animal abundance and certain forest characteristics such as snags, woody debris and vegetative structure, will be reported, Strong says.

"When you study wildlife, you need large acreage," Strong says. "Especially when looking at birds, chipmunks, mice and salamanders, which are real indicators of forest change."

Strong says the study also involves building deer exclosures to help address the impacts of deer on vegetation. Deer trail surveys will be used to index browsing on study sites by deer during the winter months.

Forest management goals vary widely depending on the forestland owner. Publicly owned lands in Wisconsin are managed to meet a variety of goals including recreation, aesthetics, timber harvesting and biological diversity maintenance. Results from this study may provide managers with sound biological and economic information on management alternative silvicultural options to meet distinct forest objectives. If these experimental treatments show that providing old-growth conditions can increase plan and animal diversity while sustaining harvests, then these approaches will be an important management option for land mangers in northern Wisconsin.

The future of old-growth in Wisconsin

Recently the Wisconsin Department of Natural Resources formed an old-growth guidance team comprised of representatives from endangered resources, forestry, wildlife management and research. Darrell Zastrow, director of the DNR's Office of Forest Science, says the first goal for the team is to define and characterize types of old-growth and old forests in Wisconsin.

"In addition, the team will develop management guidance for old-growth and mature forest management on public lands that will also be available for private landowners who desire these conditions," Zastrow says. "The team is making progress and plans on issuing its first report in 2005."

Protecting the remaining old-growth forests and managing lands to promote old-growth development is important to society. However, nothing remains static, and forests are no exception. Forests go through natural changes over time – some slow and subtle, others swift and catastrophic.

Though nature preserves can harbor old-growth forests we shouldn't rely on these small parcels as the sole places to sustain this unique plant community. Properties change over time, and sometimes drastically as from a passing tornado.

Our abundant managed lands may not have all the ecological "pieces" we associate with an old-growth forest. However, some of these lands can be harvested in such a way that they will provide many of those pieces while still providing commercial wood products – sustaining a wide range of ecological and economic values.

"While the study is long-term (50 years of monitoring) and will extend beyond most of our careers, we are always learning something new," Strong says.

Natasha Kassulke is the associate editor of Wisconsin Natural Resources magazine.