Managing woodlands in the Oak Savanna

Creating climate refugia

Models of the state’s future climate may not favor the survival of some species you currently see in your woods. However, that doesn’t mean these species don’t hold intrinsic ecological, cultural or economic value. You can work to retain these species in your landscape and protect them from the impacts of climate change by creating forest refugia.

Species in this region that may be most vulnerable to climate change, pests and diseases:

• Black maple (Acer nigrum) closely resembles sugar maple and can be found growing in a variety of sites but prefers moist soils and some shade. Consider retaining black maple on cool, moist sites and promoting a diversity of other hardwood species.
• Black ash (Fraxinus nigra), white ash (Fraxinus americana) and green ash (Fraxinus pennsylvanica) are projected to do well in warmer and wetter climates but are all extremely vulnerable to emerald ash borer. Black ash is a cultural and ecological keystone species in northern Minnesota and is an essential part of Minnesota’s forests. If ash is present in your woodland, learn more about managing ash woodlands in response to emerald ash borer.
• Paper birch (Betula papyrifera) is projected to be vulnerable to climate change in this region. Retain existing birch in diverse stands with a mix of species, age classes, and structures. Paper birch is shade intolerant and therefore prefers full sun. Consider thinning, single tree, or group selection harvests to improve the resilience of birch forests. Learn more about managing birch forests.
• Blue beech (American hornbeam, musclewood; Carpinus caroliniana) is projected to be vulnerable to climate change in this region.  This species is often found in the understory of hardwood forests and therefore tolerates full shade. Consider thinning from below to open up growing space in the understory for this species.
• Butternut (Juglans cinerea) is projected to tolerate a changing climate, but it is extremely vulnerable to butternut canker, a fungal disease that has devastated populations of butternut across the northeast U.S. butternut is a Minnesota endangered species and therefore cannot be bought commercially. A permit from the Department of Natural Resources is required to collect, transport, or possess butternut seeds and other parts of the tree. 
• Eastern white pine (Pinus strobus) is an iconic Northwoods species projected to be vulnerable to climate change in this region. Consider thinning existing pine stands to promote sufficient growing space. Harvesting in gaps can also promote a diversity of species, age classes, and structures that will improve the resilience of the stand. Eastern white pine is preferred by deer, so bud capping or tree tubes can help increase seedling survival. Preventative pruning can also help to protect young white pine trees from white pine blister rust. Learn more about managing white pine forests.
• Bigtooth aspen (Populus grandidentata) and quaking aspen (Populus tremuloides) are projected to be vulnerable to a changing climate in this ecoregion. Both species regenerate by root suckering (sprouting), and these aspen stands provide many benefits to wildlife throughout their life cycle.  Harvesting in gaps can also promote a diversity of species, age classes, and structures that will improve the resilience of the stand. Learn more about managing aspen forests.
• Northern red oak (Quercus rubra) is a species in the red oak group and is therefore more susceptible to oak wilt. Find the current oak wilt risk for your region.
• Slippery elm (Ulmus rubra) and rock elm (Ulmus thomasii) are also projected to do well but are susceptible to Dutch elm disease. With no disease-resistant cultivars of slippery elm currently available, landowners should be cautious in choosing where to encourage these species.
• American basswood (Tilia americana) is a critical component of Minnesota’s maple-basswood forests, also known as the Big Woods. This species is projected to be vulnerable to climate change in this region. Basswood prefers well-drained soils and can tolerate intermediate levels of shade. Consider managing existing basswood stands through thinning and/or single tree or group selection harvesting to improve the resilience of the stand. Learn more about managing northern hardwood forests.
• Black willow (Salix nigra) is commonly found in wet areas, including along the margins of ponds and lakes. Black willow provides food and habitat for many species of wildlife, including birds, mammals, and insects. This species is projected to be vulnerable to climate change in this region. Black willow is projected to respond somewhat poorly to a warmer climate, so consider promoting this species on cool, moist sites. 

Potential future tree species

As our climate changes, some tree species might be able to move into new areas as habitat becomes more suitable. Climate scientists with the USDA Forest Service have identified tree species with migration potential in the Oak Savanna.

Planting species not historically found in the region does carry some risk. Before you plant, learn more about assisted migration strategies, and work with a forester or another natural resource professional to determine the best options for your land and goals.

Woodlands of Minnesota Handbook

The Minnesota Department of Natural Resources has created a series of woodland handbooks that provide landowners with information on their region’s conditions, frequent challenges, and advice on setting and reaching management goals. The Oak Savanna handbook includes information on wildlife, plants, invasive species, geology, landscape and watershed management for this special region of southeastern Minnesota.