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Forest Health Overview
Generally, Michigan's forests are quite healthy and productive. Problem areas do occur in types that are beyond pathological rotation age. This is especially true in even-aged stands. Foresters are now attempting to mitigate age class distribution to reduce this risk. Forest stressors add to declines which may exacerbate an already difficult situation.
Northern pin oak in the northern lower peninsula is in a state of decline and has been since the early 1990s. Oaks growing on better sites are for the most part healthy and vigorous. A white birch decline detected earlier this decade is showing significant signs of reversal, especially on richer less disturbed sites. Birch continues to be a very difficult species to regenerate. On the other hand, northern hardwood, a type dominated by sugar maple continues to be healthy and contributes significantly to Michigan's overall forest health.
During 1994, statewide survey plots were established to monitor the health of Michigan's forests. This is a part of a nationwide Forest Health Monitoring Program in partnership with the Environmental Protection Agency, the US Forest Service and the University of Michigan. The motivation to monitor the health of forested ecosystems grew out of the concern over the potential effects of air pollutants, insects, diseases and other stressors. An additional factor was the concern over the potential effects of global climate changes to the composition and stability of forests. The monitoring program is a network of permanent plots and surveys of both forest pests and other stressors. Many other surveys are conducted to supplement this information. This monitoring will help measure change over extended periods of time.
Recent occurrences impacting Michigan's overall forest health have included significant statewide storm damage during 1995; an expansion of gypsy moth defoliation into more counties; an outbreak of larch casebearer defoliation affecting tamarack from the central upper peninsula to Gaylord; and lesser, more localized problems caused by oak leafskeletonizer, cherry scallop shell moth, and various oakworm species. These latter pests are not expected to greatly affect our forests.