Non-Forested Wetlands

Within northern Michigan, upland spruce-fir forests are typically confined to areas with shorter growing seasons and lake-effect snow and fog. Water temperatures of the Great Lakes are increasing faster than air temperatures, so lake-effect fog may become less common during the growing season. Uncertainty exists for snowfall levels in northern Michigan, particularly for lake-effect snow, but it is projected that snowfall will decline by the end of the century.

In areas that become particularly dry and fire-prone, open woodlands could transition to a more barrens or prairie-like structure. However, if closed woodlands also become drier and more fire-prone, they could transition to a more open woodland structure. In these new areas, overstory woody species may do better than understory herbaceous species because many of the herbaceous species are not present in the seedbank and have a limited ability to disperse.

Sericea lespedeza outcompetes native vegetation, particularly in the western part of the assessment area. No models have been developed to address sericea lespedeza's response to a changing climate, but inferences can be made based on its known tolerance to drought and fire. Increased sericea lespideza abundance could reduce regeneration of tree species and change community structure.

Forest impacts models do not project a substantial change in habitat suitability for eastern redcedar under a range of climate scenarios. However, eastern redcedar is already expanding in the area due to fire suppression and will likely expand further.

Forest impact models with scenarios and models that project a greater increase in warming and drier summers tend to suggest a decrease in habitat suitability for red oak group species. Forest impact models with scenarios and models with milder increases in temperature and wetter summers tend to suggest that conditions will be favorable for red oak group species. Oak decline is expected to remain a threat to the red oak group, and may become a larger threat to trees that become stressed by increased drought frequency.

Multiple impact models agree that these species will do well under a range of climate scenarios. However, southern pine beetle could also increase, posing a threat to shortleaf pine, especially in dense stands.

Open woodlands are similar to closed woodland systems, but receive more frequent fire and tend to be on flatter ridge-tops. Most of the species in open woodlands are highly tolerant of drought and fire, and may have reduced competition from more mesic, fire-intolerant species if fires and dry conditions increase. Projected early-season increases in precipitation that result in vegetation growth followed by summer drought may increase fire probability.

Some sites currently characterized as dry-mesic forests could transition to a closed woodland structure if conditions become drier and fire becomes more frequent later in the century. The extent to which fire is a component of the system may ultimately determine the success of this community type. If the system experiences very frequent fire, this system could benefit or undergo transition to an open woodland.

Although specific model information is lacking, most invasive species are expected to benefit or see no detrimental effects of climate change. However, one of the many invasive plants, garlic mustard, is relatively drought-intolerant and could decrease if conditions become significantly drier during the growing season.

Past fire exclusion has led to an increase in woody species in the understory. This change in composition has suppressed regeneration of overstory species in the eastern part of this community type’s range, and suppressed herbaceous species establishment in the western part. An increase in fire frequency could help reduce this stressor.