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Article #104, February 2006
By Bill Cook

     Forest management practices vary considerably across forest types, site conditions, market availability, and many other factors. There simply is not any single way or best way to manage all forests, or even a particular kind of forest. While nature is a dynamic system that defies simple categorization, there remains a body of knowledge and experience that can be very effectively applied.  

    Aspen stands are among the easiest to manage and regenerate. However, that does not mean they are without potential difficulties. Aspen requires full sunlight for a new stand to grow. In nature, these conditions occur following wildfire, epidemics, mass windstorms, and the like. With management, these conditions are provided through clearcutting.

     Of course, some folks react to clearcutting with a gut wrench. However, a healthy ecosystem and the rules of nature have nothing to do with visual quality. As hard as it might be for some folks to accept, clearcutting is the only way that we are going to maintain aspen in our modern forest landscape. Alternatively, forest clearing for land development is not forestry. That's a land use change involving deforestation. Clearcutting, in forestry, is a regenerating activity. It creates a new forest.

     Following a clearcut, dormant buds on the aspen roots respond to the lack of chemical inhibitors from the overstory and the warmer soil surface. These root suckers grow very rapidly with the infrastructure of an intact parent root system. With full sunlight, aspen can grow several feet during each of the first few years.

     For a decade or so, the harvested area appears brushy. This habitat is excellent for a wide variety of wildlife, including some of our favorite game species. Eventually, the young aspen enter a natural thinning stage. The less vigorous trees die from the shade cast by the faster growing individuals.

     During the younger periods of stand development, aspen may appear to be the only species. In fact, in most cases, there are many other trees mixed with the aspen. Most of these species will survive in the light aspen shade and outlive the majority of aspen in the stand. Eventually, the true biodiversity of the stand will stand out. It's usually there, even if it can't be casually seen.

     Of 15 common forest types in Michigan and northern Wisconsin, aspen ranks the fourth highest in tree species diversity. The notion that aspen forms monocultural stands is largely the result of shorter-term visual perception. The stands created through management are not terribly different from those created by nature.

     Quaking aspen matures somewhere between the ages of 40-60 years. Bigtooth aspen can remain sound for another decade or two. In either case, the species are considered short-lived as far as trees go. On better quality sites, the lifespans will be longer. On poorer sites, the trees won't grow well and will die younger.

      Once the stand becomes mature, the decision to clearcut must be made, again, if aspen is to remain on the site. Now, without a clearcut, the stand will most likely succeed into another forest type. This is not necessarily a bad thing, if the new forest is acceptable to the owner. The succeeding forest type might consist of balsam fir, red maple, white pine, northern hardwoods, or other more shade-tolerant trees. The understory will tell you what the next forest might be. In some cases, the next forest might not consist of trees, but mostly of brush.

     While clearcutting is the only way to regenerate aspen, the area does not have to be in squares and rectangles. Visual quality can be enhanced by running harvest boundaries along topographical lines and the edges of different forest types. Islands and corridors can be left to break-up the harvest area. Sometimes, a limited number of longer-lived trees can be left dispersed across the area.

     The natural ecology of aspen regeneration calls for very large "clearcuts," sometimes several thousand acres in size. In today's ownership and user environment, this natural scheme is unacceptable. With high aspen prices in many regions, clearcuts might be commercially harvested as small as 10 acres. Pockets under five acres are not advisable because adjacent trees will shade the regenerating area. It does not take much shade to significantly retard aspen growth.

     Aside from shade, there are few reasons that aspen regeneration will fail. In areas of very high deer pressure, browsing has eliminated even vigorous regrowth. Also, if aspen is harvested when it is overmature, the root systems may not be as successful at supporting new suckers. If this becomes an issue, it is best to cut aspen during the fall or winter when the maximum amount of food reserves are in the roots. Lastly, aspen on inadequate soil types may not regenerate well.

      The arguments surrounding aspen management ought not to be about clearcutting, which is an essential forest management system, but rather about the amount of aspen we want across the Lake States forest. Several hundred years ago, there was much less aspen in the landscape than we see today. Yet today, we have about half the aspen of 75-100 years ago.

      Aspen is a critical habitat for many popular species of wildlife. The wood can be used to produce a variety of products, such as paper, oriented-strand board, and cardboard. Solid wood is used in a wide variety of ways. The light gray bark, trembling leaves, and bright yellow color in the fall make aspen visually appealing. The species is one of the most utilitarian in the Lake States.

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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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