The New Old Forest

Jodi Forrester got the call while she was in the forest. The loggers were ready to go. So on a cold winter day in northern Wisconsin, she found herself riding shotgun in a harvester. Forrester, a research scientist in forest and wildlife ecology, watched as the loggers cut down the trees she and her team had carefully selected in the Flambeau River State Forest. Another huge vehicle, a forwarder, clambered behind, pinching the cut trees in its claw and moving them to where they were needed. All the while, the loggers played a little game, dodging between laundry baskets placed around the forest floor to catch leaves and falling debris. In the end, they managed to avoid all but a few.

It was not a typical job for the loggers. Instead of harvesting trees for timber, they were taking part in an experiment—the second phase of a research project on a large scale. Under the supervision of CALS forest and wildlife ecology professor David Mladenoff, Forrester and her colleagues had already been working for years to plan a forest experiment that would stretch over almost 700 acres. The loggers were there to implement that plan. Because all the wood they were cutting was going to be left in the forest as part of the experimental setup, the loggers were not able to remove any of it. It went against their nature.

“Every once in a while, the loggers had to cover their eyes,” says Forrester with a smile. “There are a lot of beautiful, valuable trees in that forest, and I think they weren’t too sure about what they were being asked to do.”

But the loggers had agreed to the job because they knew it was part of an experiment that would push the science of forest management in Wisconsin forward. All the work, including the tough job of watching the wood get left behind, was being done in the name of science—specifically, in the name of bringing the characteristics of old-growth forests back to the state.

Old-growth forests have been a scarce sight in Wisconsin since the early 20th century. Clear-cutting in the late 1800s and early 1900s left few old-growth stands. In the Upper Midwest, most big trees had been cut down by the 1930s. In the place of those stands, younger second-growth forests emerged.

Starting in the 1980s, a push to promote and protect old-growth forests picked up steam. It started in the Pacific Northwest, where obligate species, such as the spotted owl, live only in old-growth forests. As the interest in these forests moved east, people in the Midwest began recognizing the valuable ecosystem services provided by old-growth forests, such as storing carbon, maintaining soils and fostering biodiversity in plants, animals and microbes by offering needed habitats.

In Wisconsin it wasn’t a matter of protecting old-growth forests, it was a question of creating them again, or at least some of the functions they provide. And that was no small task. Creating old-growth forests requires defining them, and even that can be difficult. It’s not just a matter of age—and age doesn’t always mean the same thing. A 40-year-old aspen forest would be old, notes Mladenoff; a 40-year-old sugar maple forest, on the other hand, would be quite young.

“It’s not always the age that matters,” says Mladenoff. “Sometimes what really matters are the characteristics and features of the forest.”

With the features of Upper Midwestern old-growth forests unclear, Mladenoff and scientists at UW–Madison, other UW campuses and the Wisconsin Department of Natural Resources (DNR) in 1992 started Phase 1 of what was dubbed the Old Growth Project.

Phase 1 was a comparative study. The researchers looked at forests of various ages and histories—a total of 46 different areas—to determine what was unique to the older, unmanaged forests. They considered features like plant and tree species and sizes, woody debris on the ground, snags or standing dead trees, soil characteristics and forest wildlife. Different scientists looked at different aspects, the collaboration creating a complete picture of the forests.

After a decade of collecting and comparing enormous amounts of data, Mladenoff and his colleagues found that many of the features of old-growth forests had to do with two structural elements: the size and distribution of gaps in the forest canopy and coarse woody debris—sizable logs—on the forest floor.

Gaps are openings in the forest canopy caused when large trees fall. With sunlight able to reach the forest floor, these areas become places of regeneration and growth, and the diversity of understory plants is often higher in gap areas than in the surrounding forest.

Coarse woody debris, meanwhile, provides shelter for salamanders, insects and other small animals as well as food for fungi, insects and even other trees like hemlock and yellow birch. Logs also sequester carbon on the forest floor and reduce the amount of carbon dioxide returning to the atmosphere.

“We wanted to explore the importance of those two elements in more detail,” explains Mladenoff. “We wanted to know if creating those structural elements in second-growth northern hardwood forests could restore functional old-growth characteristics.”

Phase 2—The Experiment

Mladenoff, Forrester and their colleagues—including Craig Lorimer and Tom Gower, emeritus and former CALS professors of forest and wildlife ecology, respectively—wanted to address that question using an experimental setup. Phase 2 of the Old Growth Project, the Flambeau Experiment, was born. The first step of that phase, however, was not a trivial one. They had to find a piece of land on which to conduct the experiment. They needed a site that was big enough for all the treatments they envisioned and that would otherwise be undisturbed for a long period of time—50 years, in fact.

With help from the DNR, Mladenoff and his colleagues used geographic information systems—GIS—to look at forests at different sites to find one that would fit the bill. After two years of looking, the researchers, including a postdoctoral student dedicated to the project, finally chose the site in the Flambeau River State Forest—a hardwood stand around 100 years old, dominated by sugar maples.

Before the experimental treatments were applied to the newly found forest, pretreatment data were collected. Scientists could then compare the data collected after treatment to this baseline information. Forrester and her colleagues, including several graduate students, used grids that they laid on the forest floor to count and catalog understory plant species such as trout lilies, wild leeks, nodding trillium and jack-in-the-pulpits. They also observed and measured tree species and diversity, leaf litter that fell in the forest, nutrient cycling, activity of soil microbes and more.

Finally, after spending two years looking for a site and two more years collecting pre-treatment data, the Flambeau site was ready for treatment in January 2007. In came the loggers and machinery to create the canopy gaps and coarse woody debris. The researchers also put up fences surrounding some of the plots to exclude deer and remove their influence from those treatment areas.

For five years after Forrester first rode shotgun in the harvester, she, graduate students and other scientists worked year-round to collect data. In the winter, researchers made the four-hour trip from Madison to Flambeau to check equipment, take measurements, replace batteries and mend fences. Once the spring thaw came, their work ramped up.
A typical summer day in the forest lasted about 10 hours. The scientists would ride from their rented cabins to the Flambeau Forest, walk about a half-mile to the research site and start collecting data. These days would last until October or November, when the researchers would start to see the orange vests of hunters.

“We’d head out in the morning and take our lunch and everything we needed for the day,” says Forrester. “We’d walk into the site, do our work, then head back to the cabins and crash.”

Their work included collecting a huge number of plant and soil samples. Without any university buildings at the Flambeau site, Forrester and her colleagues had to transport all of those samples back to Madison in their vans. Once back on campus, the samples and data needed to be analyzed and entered into spreadsheets.

“We have gobs of soil and wood samples, and we employed a lot of undergrads to help us,” says Forrester, laughing. “Some folks would help in the field in the summers and then continue working in the lab in the fall while they took classes.”

Ten years into Phase 2, Forrester, Mladenoff and their collaborators are just now beginning to shape a picture of the effects of their treatments. While a decade seems like a long time for research, they have another 40 years ahead of them. Such is the course of a 50-year experiment. And researchers have a vast array of forest components to consider and measure.

At this point they have some preliminary data and even some surprising results. One of the unexpected outcomes has been in the plots with coarse woody debris. While the researchers were expecting that the effects of woody debris would take years to recognize as the wood decayed, they are already beginning to see changes in the carbon dynamics. The woody debris affected rates of decomposition and what kinds of microbes were present in the soil, for example, within just a few years after being left on the forest floor.

“I thought someone else would be seeing what happens to the wood in the future, that I would just be seeing the effects of the canopy gaps,” explains Mladenoff. “But it didn’t turn out that way.”

The researchers are also seeing more expected results. Saplings and understory vegetation are growing more quickly in areas with canopy gaps and more light, for example. Also, the deer exclusion fences make a difference. In areas without the fences, the deer are eating all of the sprouts growing from the stumps of harvested trees, which can change the composition of the forest, leaving more of the less palatable and lower value trees such as ironwood.

After five years of intense sampling after treatment, the researchers are now spacing out their measurements and sampling to allow the forest time to grow, settle, decay and cycle. With such a long-term experiment, some of the time must be spent waiting.

That time will also be spent securing funding for the project as it goes forward. The DNR provided money both for Phase 1 of the project and to get the experimental Phase 2 going. That initial funding for Phase 2 allowed the researchers to do the preliminary work, after which other funding started flowing in.

“The DNR was really helpful in getting this project started,” says Forrester. “They provided all that base funding for us to get established, and only once we started were we able to get other money.”

The USDA has provided a five-year grant, and Mladenoff and his colleagues have also received funding from the Department of Energy and USDA McIntire-Stennis grants for graduate students. Forrester is now working to secure funds for the years ahead.

The USDA grant afforded Forrester and her colleagues an unexpected benefit—the opportunity to teach a new generation of forest ecologists. The grant was awarded based on their proposal to integrate an educational component into their research, and to fulfill that aspect, Forrester created a summer internship program. Undergraduate students from around the country and the world, most with little experience in forest research, joined the scientists in the Flambeau.

“Initially we taught them the basics of forest ecology measurements and had them help us with our measurements,” explains Forrester. “As summer rolled on, we helped them focus on a topic and develop an independent study project.”

Around 40 students participated in the program over the four years it was available. At the end of each summer, they’d hold a symposium to allow the students to present their work and interact with the scientists. The graduate students gained valuable mentorship experience. It was a beneficial experience for all involved, and one that both Forrester and Mladenoff discuss with pride.

“It was an important part of the project, and it turned out to be a really great component of those summers,” says Forrester.

DNR Collaboration

In addition to providing funding, scientists at the DNR are also long-term collaborators with CALS researchers. They are working on a parallel 50-year project called the Managed Old-Growth Silviculture Study, or MOSS. Silviculture is the practice of managing forests to meet various needs or goals.

Having worked with Mladenoff and his team from Phase 1 of the project and into Phase 2, the DNR wanted to look at many of the same elements of old-growth forests, but with a more operational spin. They wanted to find out how to create the characteristics of old-growth forests while also allowing for economically beneficial harvesting of timber.

“There were three objectives for the MOSS project,” says Karl Martin BS’91, a former wildlife and forestry research chief at the DNR who is now with UW–Extension as state director of the Community, Natural Resource and Economic Development (CNRED) program. “We wanted the study to be applicable to the forest industry, we wanted to do something on a large scale so we could look at impacts on wildlife, and we wanted to show this was economically viable from a commercial standpoint.”

Martin worked closely with Mladenoff and other CALS and UW scientists to collaborate on the parallel MOSS project. One of the three MOSS sites is just north of the CALS site in the Flambeau River State Forest, with the two other sites located in the Northern Highland American Legion State Forest and the Argonne Experimental Forest.

Many of the treatments used on those three tracts of land are the same as those the CALS team is using in their experiment—canopy gaps, coarse woody debris and deer exclosures. The MOSS project also considered snags, or standing dead trees, which are another feature of old-growth forests.

Before establishing the treatments, Martin and his team spent several years surveying and measuring the trees. Because they wanted to harvest timber, they had to carefully consider which trees would be cut down and which would be left behind. Yellow birch trees were rare in the sites, so those were immediately off the table for harvesting. They also wanted to avoid cutting down the largest trees in the stands. To establish snags, the researchers chose crooked or highly branched trees that were of low economic value. While such trees make good habitat for wildlife, they are most likely to be used for low-valued pulpwood or firewood if harvested.

“We took three or four years before treating to really get things in place,” says Martin. “The problem with a 50-year study is that if you rush into it, you’re going to look back and wish you’d done something differently. We really wanted to cover all our bases.”

As with the CALS study, MOSS is in the early stages of gathering data and there are many angles to consider. The economic viability of silviculture that encourages old-growth characteristics is one of the main questions MOSS aims to answer, and Tom Steele MS’83 PhD’95, director of the Kemp Natural Resources Station in Woodruff, has been instrumental in finding that answer. Early data suggest that treatment cost of traditional harvests and the MOSS harvests is similar. In addition, the difference in timber revenue that a landowner would receive is quite minimal—just a few percent.

With years ahead to uncover the economics of such a system, MOSS is well positioned to understand and implement silviculture systems that are both economically and ecologically viable. That, in the end, is what the CALS–DNR collaboration is all about. It’s a partnership that brought about an otherwise unlikely project.

“The idea behind the collaboration is to leverage the resources of both organizations to help the citizens of the state,” explains Martin. “The scale of this study would not have been possible without the partnership of the university and the DNR. You need those resources, both intellectual and financial, to come together in a cohesive project.”

The size and scope of the Flambeau Experiment and MOSS are what make the projects so powerful—and so promising. There are decades of study ahead for researchers, and many of the original scientists will have to pass the project on to new researchers before it’s over. But the goal is clear: To determine if diverse ecosystems of old-growth forests can be developed through management while allowing for sustainable timber harvests. The outcome of the projects will have major impacts on forest management and harvests as well as on property owners, residents and visitors.

“With long-term studies, we work in the present, build on those that came before us, and count on colleagues in the future to continue the work,” says Mladenoff. “This research will be essential for long-term sustainable ecosystems and the services they provide.”

Forestry technician Donald Radcliffe BS’15, who graduated with CALS degrees in forestry and life sciences communication, contributed to reporting this piece.

Five things everyone should know about . . .The Tension Zone

1.  You will not suddenly develop migraines upon entry. Rather, a “tension zone” describes a geographic area that marks a change from one type of vegetation to another, with species from both areas intermingling in that zone.

2.  There’s a pronounced tension zone in Wisconsin. It stretches in a loose S-shape from Burnett County in the north all across the state, ending in Racine County in the south. Wisconsin’s tension zone marks the crossover between the Northern Mixed Forest—closely related to the forests of northeastern Minnesota, northern Michigan, southern Ontario, and New England—and the Southern Broadleaf Forest, which is more like forests you’d see in Ohio and Indiana. In the tension zone you’ll find plants and animals representing both of these forest types. Before the landscape in the south was developed and converted to farms, you would have seen primarily open oak savanna with forest and prairie.

3.  It’s mostly about climate. The tension zone is marked by a
climatic gradient, with cooler, moister conditions to the north and relatively warmer, drier conditions to the south. Up to the 1800s, these southern conditions were more favorable to higher populations of Native Americans—and they were a greater cause of fire, both purposeful and accidental. This maintained more open conditions in the south.

4.  It’s a fruitful area for research. John Curtis, a famous Wisconsin plant ecologist, and his graduate students in the 1950s identified the tension zone as a place where relatively more plant species had their northern and southern range limits. His book, The Vegetation of Wisconsin (1959), talks about this and includes a map of the number of species reaching their limits in each county. Today, researchers are again very interested in the tension zone because of changes in land use that have endangered some native plant species. Also, with climate warming, the area is of interest to both climate scientists and plant ecologists, who are looking at how the tension zone is and will be moving north—and its potential effects on ecosystems.

5.  You’ll know you’re in the tension zone when you’re heading north and … oaks that are dominant in southern Wisconsin, such as Bur, black and white, meet up abruptly with red and white pine as well as paper birch and tamarack swamps that are more characteristic of the north. Shagbark drops out completely and bitternut hickory becomes much less common. You’ll start seeing some birds that are absent or relatively uncommon in the south: common loon, ruffed grouse, osprey, common raven, white-throated sparrow and purple finch. You’ll also encounter northern mammals: snowshoe hare, porcupine, red squirrel, black bear and timber wolf.

David Mladenoff is the Beers–Bascom Professor in Conservation in the Department of Forestry and Wildlife Ecology