Regeneration

While forest management systems are designed to stimulate tree regeneration, seedlings face new threats to survival.

The Michigan Society of American Foresters recently held a conference about forest regeneration. Foresters, perhaps more than any other group, tend to worry about what the next forest will look like decades in the future.

A century of research and practice has produced a set of management prescriptions that effectively regenerate our Lake States forests, and also provide wood products, forest health and a wide range of other environmental and social services. These management systems are designed to provide forest conditions that favor the natural regeneration of trees. Trees are actually good at reproducing themselves when given a chance.

Management systems must be tailored to different forest types. There is no “one size fits all” approach. The Lake States forest consists of a wide range of forest types, each with their own set of ecological requirements. Shade tolerance, disturbance, a seed source and seed bed conditions are four key variables for regeneration. However, the heart of forest management is a science called silviculture, which is the study and practice of forest ecology to provide all the goods and services that society demands. Regeneration is at the root of silviculture.

For many decades, the application of particular practices, under appropriate conditions, regenerated forests with a high degree of reliability. Aspen and jack pine are two species that evolved with major disturbances and require full sunlight, so clear-cutting was employed to mimic natural circumstances. Sugar maple, beech and basswood forests, on good sites, are species that do much better with a selection system, which mimics smaller disturbances common in these kinds of forest types. Foresters evaluate forest conditions, take into account forest owner goals, and then design management plans accordingly. It is a rewarding experience for both the forester and the forest owner.

Unfortunately, according to Michigan State University Extension, there are several threats to forest regeneration and some of the traditional management systems may no longer yield the expected results. Facing foresters are altered successional pathways, novel forest communities, and a less predictable future. Failure to regenerate forests could result in the loss of forest certification status, which would threaten a regional industry worth tens of billions of dollars.

Deer pose a huge threat, but this idea is a hot-button issue for many. In 2007, a survey revealed that the majority of Michigan foresters perceive deer depredation as a significant threat to forests. Ecological research literature across North America clearly supports this premise. Deer are, of course, a very natural part of Lake States forests and a crucial part of our hunting heritage. Their populations also vary widely across time and geography. However, long-term over-browsing translates into long-term negative impacts that are not easily reversed, even if the deer impacts were removed from the forest.

Exotic species, animals, plants and fungi, are wildcards in their impact on forest regeneration. Research into known species impacts reveals a range of outcomes. Unfortunately, each new species can potentially change the game a bit more or, in some cases, dramatically. The exotics often work in concert with each other, and sometimes with native species, to alter seed bed conditions to the point that some native trees may not be able to adequately regenerate.

For example, earthworms, slugs and certain shrubs (exotic players) will work with small rodents and deer (native players) to discriminate against the regeneration of native ground flora and tree species. Simple elimination of the exotic species may not result in the restoration of natural conditions.

Forest parcelization (ownership) and fragmentation (permanent canopy disruption) change forest structure, composition and function. Smaller parcels and higher numbers of owners in a particular area make for an increasingly difficult and expensive opportunity for management and restoration. The human element also accelerates exotic introductions and, in many cases, higher deer numbers.

All of these ecological dynamics exist in an era of rapidly-changing climate conditions. As current trends continue with precipitation, temperature, wind and growing seasons, so changes the forests. Nobody is confident in defining these changes, but nearly everyone knows that change is occurring.

Lastly, benign neglect of forests (doing nothing) allows all these agents to operate unchecked, sometimes with undesirable outcomes for both the forest and human society. Benign neglect may also allow native pests and diseases to unnecessarily gain the upper-hand. These pests evolved with our native forests. However, the forests have changed considerably over the last two hundred years and relationships between the forests and pests have changed.

New forest stressors work with the usual stressors in both predictable and currently unpredictable ways. The massive historical disturbances associated with the Lake States logging era will likely pale in comparison with the challenges our forests face in coming decades. That sounds like a long time, but for foresters, it is not much more than the blink of an eye. 

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