DNR experts explain the value of forest inventory

Logs piled up on a timber site in Marquette County, ready to be hauled out.

April 19, 2016

Store keepers take inventory. Car dealers take inventory. Fast food restaurant managers take inventory, and Michigan Department of Natural Resources foresters take inventory, too.

Each year, DNR foresters survey roughly 400,000 acres of state forest lands to find out what’s there. Over the course of a decade, the state’s entire 4 million acres of state-managed forest land are inventoried.

“An inventory is basically a compilation of information that a landowner knows about the forest,” said Jason Stephens, forest inventory specialist for the DNR’s Forest Resources Division.

Michigan leads the wayAgainst a blue autumn sky, logs are being moved on a Mackinac County logging operation.

Stephens said the DNR began compiling inventory data on every acre of state forest in 1978. Nearly four decades later, Michigan has emerged as a national leader among forest management agencies in its approach to inventory.

“The amount of time we invest in forest inventory is beyond what anybody else is doing,” Stephens said. “We have a tradition of managing forests the best we can to meet the needs of our society, using continuously updated information.

“From recreational users who want to know the hiking paths are in good shape, to the grouse hunter who wants to make sure the aspens aren’t getting too old, to the sawmill operators who want to make sure they have adequate trees for their mills over the next 30 years, we provide the information they need.”

That doesn’t mean the DNR knows exactly how many trees it has. But it does mean the department has a pretty good idea of the composition of tree species and the overall volume of timber in Michigan’s state forests.

Inventory methods

When detailed measurements are needed, foresters survey stands at about 1 point per 10 acres, using instruments that tell them the density (stocking level) of the trees.

The stocking level could be the same for a stand with five trees or 50 trees; it depends on the circumference of the trees.

Workers moving wood through the milling process.But not all forest tracts are inventoried the same way.

“There are stands where we don’t take these detailed measurements, stands of newly planted or sprouting trees or open habitats, like a pine barren,” Stephens said. “For these stands that are immature or of very low stocking density, we can estimate.”

Forest unit organization

The DNR maintains 15 forest management units in four districts – the western Upper Peninsula, eastern Upper Peninsula, northwest Lower Peninsula and northeast Lower Peninsula.

These units typically are broken up by county lines, though sometimes there are exceptions because of the physical geography. The Pigeon River State Forest, for example, is unique and straddles several counties, but is a single management unit.

The management units are usually named for the town where the DNR Forest Resources Division headquarters are located.

Decisions

Forest inventory data gives foresters the basic information they need to make planning decisions. These decisions are based on the forest’s biological maturity, the economic maturity and the ecological and social values of timber stands, Stephens said.

“Consider jack pines for Kirtland’s warbler habitat,” Stephens said. “We want to continually provide prime habitat for these birds that nest primarily in Michigan.”

In a similar manner, aspen is valuable for deer and grouse habitat, but it is also in demand by the forest products industry.

“It’s usually cut at around 50 years of age, but sometimes we cut it earlier because it has social and economic value,” Stephens said. “We want to maintain a consistent amount of habitat and fiber for mills.”

Improvements

Stephens said the inventory process is constantly being updated and improved.

“In the last decade we’ve changed our inventory procedure to gather much more species-specific information,” Stephens said. “Prior to that, we had more generalized forest-type information, such as northern hardwoods or lowland conifer. Now we can describe it in more detail, such as a stand being comprised of mostly fir or spruce with some northern white cedar.”

The technology of how the DNR organizes data has evolved a lot.

“It would be surprising to most folks the amount of information we have,” Stephens said. “We can describe the number of trees we planted in a stand in 1948.”

Forest treatments

About 68,000 acres of DNR-managed forest lands are prescribed for timber harvest each year.

Harvests can range from clear cuts to selective cuts where only some of the trees in a stand are cut. There are also areas of state forest that are not managed for timber, such as non-forested wetlands or grasslands. There are even some remnant forests from the early 1900s that remain uncut, which are considered old growth.

Public input

Treatments, such as timber harvests, are proposed and publicized.

Production of forest products is an important part of Michigan's economy.DNR forest management units hold open house meetings where foresters, biologists and recreation specialists are available to answer questions and describe management goals and to take public comments.

“We really value public input during the planning and review process for proposed timber sales. It is much easier to address public concerns then, rather than after a decision has been made and the timber is being prepared for sale,” said Deb Begalle, acting chief of the DNR Forest Resources Division. “Final decisions on the sites to be harvested are made at a compartment review meeting, which is open to the public.”

DNR forestry staff is inventorying forests now that are scheduled for treatment in 2018.

Refinement

The forests are going through their fifth round of inventory and the DNR is still learning new things about Michigan forests.

“Inventory is a refinement of previous work,” Stephens said. “Four million acres is a lot of land and you may get out there and find that the description doesn’t include some interesting things that you didn’t even know were there. You’re almost an explorer in some ways. The way things change over time is often surprising.”

Forest inventory has additional benefits beyond timber management, Stephens said.

“Inventory is one of the ways we can systematically stay on top of things for our land-management responsibilities,” he said. “It keeps us informed about the condition of the infrastructure – roads, bridges and culverts – and we find out things like whether an area is being used as a trash dump.”

As refinements in forest inventory continue, the public remains involved in the process and as industry methods advance, Michigan’s world-class forests are poised to remain vital, renewable natural resources for generations to come.

Michigan's 4 million acres of world-class state forest land are the backdrop for rustic recreation and exploration. They provide critical habitat for wildlife and fuel a vital timber industry. Watch a video on what these forests mean to our everyday lives.

Check out some Michigan forestry facts.

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