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Article #89, November, 2004  
By Bill Cook

     A timber harvest is commonly a once in a lifetime experience for many forest owners. Getting the job done right has long been a hand-wringing concern. While there are many variable factors to consider, the best season to harvest may be one of the most important.

     On one hand, winter seems the obvious choice. The frozen ground reduces the chance for soil damage and allows access to areas too wet during the summer. Snow might lessen the disturbance of anything on the surface. Without the leaves, trees can be more easily identified, paint marks better seen, and skidding lanes more clearly determined. Tree trunks have less moisture and are less susceptible to wounding. Wounds that do occur are less vulnerable to diseases floating around.

     On the other hand, when regeneration is an issue, summer might actually be the better season. Disturbance is frequently a key element in forest regeneration. Many of our tree seeds require exposed mineral soil for effective germination and survival. Few of our tree species have seeds that can penetrate a thick layer of leaves and coarse organic debris. Exposing mineral soil is called scarification. This process opens the window for increasing species diversity within a stand of trees.

     Winter harvest and properly done thinning in northern hardwood stands favor sugar maple. Decades of single-tree selection and natural succession has helped sugar maple dominate many of our forests. Sugar maple has long been Michigan's most common tree. It's also one of our most monetarily valuable trees.

     However, expansive areas dominated by a single species leaves the forest vulnerable in a couple of important ways. First, a downturn or change in the market could financially impact timber owners. Of course, high quality logs have always maintained reasonable or good dollar value. A stable forest industry is also essential to sustainable forest management. Second and more importantly, an exotic insect or disease that attacks maples could wreak havoc on our economy and lifestyle. And there are, indeed, a couple scary characters lurking out there.

     Tree diversity does need to be maximized in every stand, but diversity across the landscape is an essential component of forest health. When an epidemic breaks out, native or exotic, the impacts are reduced by breaks in forest composition and structure.

     Some forest types naturally trend towards low tree species diversity, such as jack pine, tamarack, and spruce-fir. Others, such as northern hardwoods, aspen, and swamp hardwoods, tend to be more diverse. This diversity, at both the stand level and landscape level, can be managed for increased forest health and human benefit.

     While the season of harvest is but one factor in establishing a timber sale, the cumulative effects over time and place can be quite important. Forest management often addresses these secondary considerations that are not immediately evident to most people. That's one reason why the services of a professional forester are always recommended. Not only does a timber sale represent a potentially large sum of money, it also represents an entire complex of ecological, economic, and social impacts. The best way to get the job done right is to hire a professional.

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Bill Cook is an MSU Extension forester providing educational programming for the entire Upper Peninsula. His office is located at the MSU Upper Peninsula Tree Improvement Center near Escanaba. The Center is the headquarters for three MSU Forestry properties in the U.P., with a combined area of about 8,000 acres. He can be reached at cookwi@msu.edu or 906-786-1575.

Prepared by Bill Cook, Forester/Biologist, Michigan State University Extension, 6005 J Road, Escanaba, MI  49829
906-786-1575 (voice),  906-786-9370 (fax),  e-mail:  cookwi@msu.edu

Use / reprinting of these articles is encouraged. Please notify Bill Cook.
By-line should read "Bill Cook, MSU Extension" Please use the article trailer whenever possible.

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