Aspen Thinning
July 27, 2001
Mike Carroll
DNR Division of Forestry
500 Lafayette Road
St. Paul, MN 55155-4044

Dear Mr. Carroll:

As I referenced at the July 24 Forest Resources council meeting, the Ruffed Grouse Society remains concerned about the potential impacts of commercially thinning mature aspen stands upon wildlife. The Society supports the application of thinning practices on the Demonstration Forest to monitor the effects on ruffed grouse, deer and other species associated with mature aspen stands. The recent revelation that thinning 25-35 year old aspen stands has been mandated outside of the Demonstration Forest could lead a thoughtful person to conclude that the Department is not fully committed to the impact monitoring that was strongly recommended by attendees at the Forest Summit. We don't know what potential impacts may exist, but we feel that the topic should be examined before widespread application of thinning is implemented on public lands.

We respectfully suggest that the Department could meet its financial obligations to the Legislature more rapidly and cost effectively by utilizing traditional harvesting methods to regenerate a portion of the mature to overmature aspen currently found on state lands. In order for the Society to evaluate the extent of thinning applications, please provide me with a breakdown of how many acres each area forestry office is expected to thin and an assessment of the acreage of aspen in the 25-35 year age class found on state lands.

One of our concerns is that thinned stands may not be clearcut upon final harvest. If young trees that sprout after the initial thinning are left standing during final harvest, they may impede root sprouting and stand regeneration. They resulting stand would have two age classes and may not provide the dense vertical structure necessary to protect young forest-associated species from predation. We would be much more comfortable with limited application of commercial thinning if the Division developed thinning guidelines that explicitly expressed the need to clearcut all aspen stems during the final harvest of the thinned stand.

The Ruffed Grouse Society is also concerned about the continuing conversion of aspen to other forest types here in Minnesota as well as across the eastern deciduous forest. Data from the USDA Forest Service Forest Inventory and Analysis suggest that Minnesota lost about 250,000 acres of aspen from 1977 to 1990, primarily due to conversion to other forest types. Since the mid-1960's, the total area of aspen in Michigan, Minnesota and Wisconsin, which contains 80 percent of the aspen in the Eastern US, has decreased by 21 percent.

The Society, and I believe the Division, recognize that actively converting aspen stands to conifers is a costly and often futile endeavor. Passive conversion through pine underplanting and chemical release is more cost effective and will temporarily lead to a mixed stand of hardwoods and conifers. However, if the stand is not clearcut at the aspen rotation age it will convert to softwoods. We ask that the Division of Forestry differentiate in the Timber Harvest Plans between situations where underplanting is an attempt to sustain mixed stands and situations where it is intended to lead to a long-term stand conversion. We also would like to see the acres of proposed aspen conversion detailed in the Subsection Forest Resource Management Planning efforts.

The Ruffed Grouse Society appreciates your efforts to properly manage Minnesota's forests for the people and the wildlife resources of the state. We will continue to provide input on how forest management can benefit the many species that utilize young forests. Please feel free to contact me if you have any questions or comments.