Exploring Northern Hardwoods
By Bill Cook, MSU Extension Forester/Biologist
“Northern Hardwoods” are forests dominated by tree species such as sugar maple, red maple, basswood, hemlock, and yellow birch. This forest type is the most common in Michigan and, arguably, the most valuable in many ways. A major study has been undertaken to better understand management systems for these forests.
Northern Hardwoods cover more than five million acres, more area than three U.S. states. That’s larger than all the state forests and about a quarter of all the forestland in Michigan. These are the forests sought by the leafpeepers in the Fall. Foresters have, collectively, spent hundreds of years thinning and improving the quality of these forests. High quality sugar maple trees command high prices. Nearly a quarter of all Michigan wildlife use these forests for at least a portion of their habitat requirements or preferences.
Northern Hardwoods are important to Michigan, as well as Wisconsin. However, they’re not regenerating well, and not with the desired level of tree diversity.
That’s why the Michigan DNR approached Gary Roloff and Mike Walters to help design a huge study of these forests across Michigan. Gary and Mike are researchers at Michigan State University. The idea is to learn how to increase sustainability and diversity.
The traditional single-tree selection management has not rendered the diversity of tree species and age classes that were the goals. Across much of Michigan and the Lake States, decades of deer over-browsing have curtailed desired recruitment of new forests. And, there may be other reasons, too.
Additionally, exotic pests, such as beech bark disease and the emerald ash borer, have removed tree species components. And, researchers are closely watching the known populations of the Asian long-horned beetle.
To develop a new model for Northern Hardwood management, the partners have fired-up one of the largest studies of its kind in history. There are 142 30-acre research plots across the Northern Lower Peninsula to the far Western Upper Peninsula on both public and corporate ownerships.
Three alternative regeneration techniques are deployed; seed trees, shelterwood, and gap selection. The seed tree method is a clearcut except for six to eight selected trees per acre that serve as a seed source for the next forest. A shelterwood harvest will remove up to 50 percent of the canopy to allow prescribed amounts of light to encourage desired tree species. Gap silviculture creates small gaps in the forest canopy, larger than single tree selection, to encourage increased tree diversity among the regeneration.
Researchers and technicians are monitoring deer browse levels and other wildlife components, from pellet counts to the use of 250 motion-activated cameras. On some plots, loggers are leaving large tops where they fall, or piling tops and branches, to provide a barrier to deer browsing. Some sites will be scarified, where machinery roughs-up the soil to provide a better seed bed and to discourage competing vegetation.
This monumental project will last at least a decade, with measurements retaken every two years. It began in 2016. A large amount of baseline data were collected in order to better assess change.
At the end of the day, researchers hope to be able to make some forest management recommendations that will move our forests into a more sustainable direction.