My Take: 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 Lower Michigan. Whether set by native peoples or from lightning strikes, fires influenced the presence of different forest plant and wildlife species. Most of our coniferous tree species such as eastern 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 the developing forests provide habitat for a number of wildlife species, including the Kirtland’s warbler, red crossbill, black-backed woodpecker, and snowshoe hare.
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. 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 the sapling (small tree growing in the understory) stage, some Neotropical migrant songbirds can be impacted. Many of these species nest in trees within 15 feet of the forest floor and if few saplings exist 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 Lower Michigan. For some tree species, climate change projections by the U.S. Forest Service suggest a shrinking distribution in Michigan. Balsam fir, aspen, and sugar maple 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. To this end, 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 Lower Michigan.
— Dr. Greg Corace is a forest and wildlife ecologist for the Alpena-Montmorency Conservation District. He assists forest landowners in northern Lower Michigan with meeting their goals and understanding how forests function. 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, ext. 102).
This article originally appeared on The Petoskey News-Review: My Take: Changing forests, changing times
