Forested watershed

Red pine is relatively drought tolerant and may not be greatly affected by more frequent moisture stress or more extensive droughts, except on the driest of sites. Moisture stress could favor jack pine or northern pin oak on already marginal red pine sites.

Multiple forest impact models tend to agree that oaks are 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 and northern pin oak. Oak forests are limited by cold temperatures in northern Wisconsin and western Upper Michigan, so warming may allow oaks to expand into previously unsuitable areas.

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. New pests such as hemlock wooly adelgid may be able to persist if introduced.

Models projections are mixed for many common species that make up northern hardwood forests in northern Wisconsin and western Upper Michigan. In particular, sugar maple, yellow birch, and eastern hemlock are projected to increase under mild climate scenarios and decrease under hotter, drier conditions. Some more southerly-distributed hardwood species that are currently infrequent or absent in the assessment area, including white oak, sycamore, sweet birch, and yellow-poplar, are projected to gain new suitable habitat.

Stand-replacing fire, typically a rare event in these systems, may become more frequent if sites become particularly dry. The potential for extensive droughts also increases the possibility for more frequent outbreaks of pests like tamarack sawfly and spruce budworm, which may subsequently increase fire risk.

These are boreal species near their southern range limits northern Wisconsin. Multiple forest impact models tend to agree that these species are more likely to decline in suitable habitat and biomass across a range of climate scenarios by the end of the century. Associated hardwood species, such as paper birch and quaking aspen, are also expected to decline. These forests may not maintain their identity if dominant species decline and water tables change.

This boreal species is already near its southern range limits in northern Wisconsin. Multiple forest impact models tend to agree that jack pine is likely to decline in suitable habitat and biomass across a range of climate scenarios by the end of the century. Overall, low species diversity gives this forest type few alternatives if conditions shift beyond tolerable limits.

Jack pine forests can thrive on droughty, nutrient-poor sites. These traits may allow jack pine forests to tolerate a moderate amount of moisture stress and disturbance due to climate change. Although some current jack pine sites may become too hot or dry in the future, other sites currently dominated by red pine, white pine, or other species may become more suitable for jack pine. Jack pine seedlings are more susceptible to drought stress than are established trees, however, and regeneration failure may occur more frequently.

These are northern species near their southern range limits in northern Wisconsin. Multiple forest impact models tend to agree that these species are more likely to decline in suitable habitat and biomass across a range of climate scenarios by the end of the century. Model results are mixed for balsam poplar and bigtooth aspen, but models agree that these species are not projected to increase substantially under future climate scenarios.

The early-successional characteristics of these species, including abundant wind-dispersed seed production and vegetative reproduction, make them highly resilient to many forms of disturbance. Disturbance from stand-replacing wildfire or wind events could benefit this forest type, although small-scale disturbances could increase the rate of succession to other forest types.