Changing Forests, Changing Times

There is a common adage that the only constants in life are death and taxes. For most of us, changes in our lives occur wherever and whenever we look: whether it be kids growing up, our local community, or the forests we take pleasure in. The history of northern Michigan, both natural history and human history, is all about change. Some of these changes have occurred slowly and steadily, while other changes have been more abrupt. Regardless, change has always occurred and planning for change should be something we all do. Forest changes are often driven by underlying workings of a forest that are collectively termed ecological processes. A forest disturbance can be thought of as an ecological process that influences what plant and animal species comprise a forest (termed composition) and how these biological units are arranged (termed structure). When a younger forest comprised of a suite of species ages and new species move in, this is referred to as forest succession. In a nutshell, changes in ecological disturbances often lead to changes in forest composition and structure and forest succession. Fire was once much more common in northern Michigan as an influence to forest succession. Whether set by native peoples or from lightning strikes, fires influenced the presence or absence of different forest plant and wildlife species depending on characteristics of the fire and the site in which the fire occurred. Most of our coniferous forest tree species such as white pine, red pine, jack pine, black spruce, white spruce, and tamarack are adapted to sites that are fire prone to varying degrees. In fact, some of these tree species have cones that open due to the heat generated by a fire (called serotiny). The seeds contained in these opened cones settle on the top layer of the soil due to the removal of the leaf litter by the fire. These seeds are then ready to germinate and provide habitat for a number of wildlife species, including the Kirtland’s warbler, red crossbill, snowshoe hare, and many others. Fire can cause abrupt change that is easily visible. On the other hand, the impacts of white-tailed deer can be more subtle. Browsing (the eating of woody plants by an herbivore) is an ecological disturbance that can dramatically influence a forest. Deer will eat different plants at different times of the year while avoiding other plants during some or all seasons. In localized areas with high deer populations, browsing can significantly reduce the abundance of many plant species. This can then have cascading effects on other plant and wildlife species. For instance, if tree regeneration is reduced due to deer browse and few trees make it to from the seedling to the sapling (small tree growing in the understory) stage, some Neotropical migrant songbirds can be impacted. Many of these species nest within 15 feet of the forest floor and if few saplings make it to this stage due to deer browse then the number of nesting sites is reduced. Forest change can also be more widespread than any given forest stand. Climate change and invasive plants and animals are influencing nearly all our forests in northern Michigan. For some tree species climate change projections by the U.S. Forest Service suggest a shrinking distribution in Michigan. Balsam fir and all three species of aspen are some of the tree species for which change may be most pronounced. What tree species will fill in the habitat space (termed niche space) is an interesting question since some tree species will surely benefit from climate change. Regardless, planning for future forests must include an understanding of our current and past forests, what causal agents of change exist, and to what extent these agents will shape the forest. For those interested in forest conservation, planning for change is critical. What is here now was not necessarily always here and will not necessarily be here in the decades to come. Future forest planning must include the enhanced integration of peer-reviewed scientific literature with localized understanding of current and past forest conditions. These efforts must be transparent and “evidencebased” and identify opportunities and limitations to management. To this end, planners can use a wealth of information readily available to evaluate past and current conditions and propose future trajectories a forest might take. Information is readily available on historic and current landscape composition as well as information on soils and the range of forest types that can grow on them. Less readily available, but still to be found, is detailed information regarding the diversity of wildlife species associated with the range of forest types found in northern Michigan. To this end, a range of different programs are provided to aid in forest planning. Interested forest landowners are encouraged to visit the Alpena-Montmorency Conservation District website and investigate what programs may best fit their needs. Dr. Greg Corace is the forester for the Alpena-Montmorency Conservation District. Greg has spent the last 25 years publishing forest and wildlife research and conducting forest planning, management, inventory, and monitoring on public and private lands across northern Michigan. For more information, including sources used in this article, Greg can be contacted via email (greg.corace@macd.org) or via phone (989.356.3596 x102).