Forest [FAR1]

In northern Michigan, barrens are typically maintained by management activities, prescribed fire, or wildfire. Conditions that promote wildfires are generally projected to become more common in northern Michigan by the end of the century. Fire suppression has contributed to woody encroachment and an increased presence of invasive species in many barrens systems. Therefore, barrens could benefit if climate change increases the frequency or severity of wildfire in xeric areas across the assessment area. Too much fire, however, could result in conversion to open grassland systems.

Barrens typically occur on excessively drained, nutrient-poor sands or on thin soils over bedrock. These systems have evolved to tolerate droughts, and they may gain territory lost by other forest types if moisture stress becomes more common under climate change. Conversely, warmer temperatures might allow species like oaks to invade barrens maintained by frost pockets.

The diversity of these forests (species diversity as well as genetic diversity) gives this forest type many possible future trajectories under changing conditions.

Under a high emissions scenario, researchers forecast more insect pest damage in northern forests due to increased metabolic activity in active periods and increased winter survival. Drought-stressed trees are also typically more vulnerable to insect pests and diseases. New pests such as Asian longhorn beetle present unknown risks. Stressed forests may also be more susceptible to oak wilt and oak decline.

Multiple forest impact models tend to agree that white oak is likely to increase in suitable habitat and biomass across a range of climate scenarios by the end of the century. Results are mixed for northern red oak, northern pin oak, and black oak. Oak forests are limited by cold temperatures in northern Michigan, so warming may allow oaks to expand into previously unsuitable areas. Many of these species are near their northern range limits in Michigan, so they may benefit from gene flow from southern populations.

Past management and wildfire suppression allowed oak associations to expand into barrens and pine forests, but continued fire suppression is allowing mesic species like red maple to invade these stands. Therefore, climate change influences on the wildfire regime and ability to apply prescribed fire will have consequences for oak associations. More surface fires could benefit oaks and allow for more natural oak regneration. A shift to more frequent crown fires could encourage a shift to pine forests and barrens.

Oak forests can thrive on sandy to loamy soils. Oaks are relatively drought tolerant and may endure more variable precipitation under climate change. These forests could gain territory lost by other forest types under drier future conditions.

Many species in riparian and lowland forests can tolerate intermittent wet and dry conditions, and they can tolerate periodic floods and moisture stress. Extended droughts would cause significant damage to shallow-rooted species, but increased winter and spring precipitation could buffer summer droughts in low-lying areas on the landscape.

Under a high emissions scenario, researchers forecast more insect pest damage in northern forests due to increased metabolic activity in active periods and increased winter survival. Drought-stressed trees are also typically more vulnerable to insect pests and diseases. Emerald ash borer and Dutch elm disease are expected to continue to limit ash and elm species.

Invasive species are generally expected to benefit from changing conditions and increased stress, but it's hard to predict exactly how they may be affected by climate change.