DNR: The sound science of using clear cuts in forests
LANSING – The Department of Natural Resources’ Forest Resources Division is in charge of managing the timber on state forest land. The DNR’s Wildlife Division is in charge of managing the critters. But because forestry practices have a big impact on wildlife habitat, the two divisions co-manage state forests to benefit both timber and wildlife.
And although the divisions sometimes have different ideas, both agree on one often misunderstood technique: clearcutting.
“Clear-cutting is a sound scientific management technique for harvesting and regenerating certain forest types,” explained Deb Begalle, forest planning and operations section manager with the Forest Resources Division. “Usually it’s for shorter-lived species – such as aspen and jack pine – which are also sun-loving species. They need a lot of sunlight to establish and grow.”
Clear-cutting involves removing virtually all the timber from a stand, which encourages regrowth of the preferred species. But it doesn’t involve stripping the landscape as it did during the timbering era.
“Clear-cutting isn’t what it was 100 years ago,” Begalle said. “We leave some trees in place for a variety of reasons – for wildlife, for aesthetics, sometimes in clumps, sometimes individual trees.
“People are averse to the look of clear-cuts. They see a lot of slash (branches, logs and other debris from natural occurrences or logging operations) on the ground and find it unsightly. But the slash puts nutrients back into the ground as the branches decompose. It also provides micro-habitat for wildlife species, such as salamanders, and brush piles for rabbits.”
DNR wildlife biologist Mark Sargent says young aspen is important to a host of species – grouse, woodcock, deer, rabbits, hare, moose, elk and numerous song birds.
“In the case of grouse, young aspen stands provide brood-rearing and nesting habitat and as they grow older, they produce winter food via buds,” he explained. “But young aspen also provides browse for deer, elk and moose – leaves, stems, tops and bark. As the trees grow larger, they grow out of the reach of the animals.”
But along with aspen, Sargent said, come other shade-intolerant plants – raspberries, forbs, dogwood and hawthorns – that provide food or cover for wildlife, too.
“A clear-cut can create outstanding browse and still provide habitat for grouse and woodcock,” he added. “It’s a winwin situation.”
The most critical characteristic of clear-cuts is that they really don’t last long.
“We always assure trees are going to grow back quickly,” Begalle said. “In the case of aspen, it will come back so quickly that within a year we have seedlings all over the place.”
Jack pine, on the other hand, generally has to be replanted. The DNR replants jack pine within two years of a cut.
Aspen is typically managed on 40- to 60-year rotations for several reasons. That’s not only when the trees have good timber value, but when they’re prime for regenerating.
“The older it gets, the less well aspen regenerates,” Begalle said. “Aspen sort of uses up its vitality. It regenerates through its root system and if it’s losing vitality, it won’t produce as many sprouts.”
Clear-cuts maximize regeneration. If an aspen stand is selectively cut, it will not regenerate as well and many trees won’t survive in the shade.
Jack pines are usually managed on 50- to 70-year rotations.
“If jack pine gets over-mature it’s prone to insect problems, such as jack pine budworm, which increases mortality and the risk of wildfire,” Begalle said. “The older it gets, the more susceptible it is to problems.”
However, not all mature or overmature stands of jack pine and aspen are clear-cut.
“We stay out of areas with threatened or endangered species or areas of particular environmental sensitivity, such as natural areas,” Begalle said. “Along water courses, we use the Sustainable Soil and Water Quality Practices manual that was produced by DNR and Department of Environmental Quality, and was last updated in 2009. It’s basically to ensure that no soils or sediments go into the streams and there is shade provided by trees along the waterway.”
Clear-cuts tend to be relatively small, averaging 40 acres, and if it’s more than 100 acres, department policy is to review the plan before the timber harvest to make sure it’s justified. Sometimes, however, larger cuts are necessary. One factor on the size of the cut is the habitat requirement by certain wildlife species, Begalle said.
“Kirtland’s warbler, for instance, needs hundreds of acres of young jack pine. So we’ll have large timber sales so we can regenerate large areas, sometimes 300-plusacre clear-cuts.”
While the cuts are well-planned, one of the things the DNR is sometimes criticized for is not leaving buffer areas around clearcuts.
“We usually do not leave buffers along private property lines, because people then think that’s the property line,” Begalle explained. “A lot people utilize or build on that uncut area because they believe the cut is the property line. And if we left buffers along all the property lines, that would leave thousands of acres unmanaged.
“We try to keep aesthetics in mind,” she continued. “If we have long-lived tree species, such as white pine and oak, we will try to leave those along roadways and private property. But if they’re short-lived trees, or in poor health, they become a hazard or die fairly quickly, and don’t serve the purpose for which they were left. We want to create a new, healthy forest as quickly as possible.”
Clear-cuts do not work for all trees, such as hardwoods or sawlog conifers.
For more information about Michigan’s state forest land, visit www.michigan.gov/forestplan.