Managing woodlands for a changing climate
Deep in the heart of Ecuador’s Sumaco Biosphere Reserve, the trees are slowly walking – very, very slowly. In pursuit of better living conditions, the trees grow new roots that stretch across the forest floor and gradually pull the rest of the tree along behind. These so-called walking palms might only move 2-3 centimeters per year, but they’ve been known to travel as far as 20 meters (65 feet) over time.
Here in Minnesota, our beloved maple trees are also on the move as Minnesota’s climate becomes warmer and wetter. During his Ph.D research, University of Wisconsin Professor Nicholas Danz documented Minnesota’s gradual maple migration over the past 150 years. While individual trees are not moving, changing climate conditions have made it easier for maples to live further north in our state. Brainerd once marked the middle of maple territory; now that point has moved north to Grand Rapids. Other species, such as aspen and tamarack, are also impacted by climate change but have proven less able to move. Instead, those tree species are slowly disappearing from our Minnesota forests.
University of Minnesota has created a woodland management field guide, Climate Change Field Guide for Northern Minnesota Forests, to help foresters and woodland landowners understand how climate change might impact different kinds of trees and forests. The guide was created in partnership with the USDA Northern Forests Climate Hub and is color-coded for easy navigation. One of the most useful features of the booklet is a table showing predictions for how different tree species will fare over time. Winners, including black cherry, eastern white pine, and white oak, are expected to increase by more than 20% by 2100. The losers, expected to decrease by 20% or more, include balsam fir, black spruce, paper birch, quaking aspen, and white spruce.
The guidebook also looks at forest ecosystems as a whole and provides an assessment of which will be most vulnerable to climate change. Minnesota climatologists note that our state’s climate has become warmer and wetter since 1895. Average annual temperature is up 2.9°F and annual precipitation is up 3.4 inches. We also have more frequent “mega rains” that drop 6+ inches of rain over 100sq miles or more. Wet forests, forested rich peatlands, and acid peatlands are particularly vulnerable to the changes in rainfall. Forest rich peatlands and acid petlands only exist within a narrow range of water table conditions and tend to transition to open peatlands (no trees) when there is too much water. In wet forests, several species require intermittent wet and dry periods to regenerate. Northern white cedar is expected to decline as warmer winters allow for larger deep populations; meanwhile, invasive pests like emerald ash borer add further stress to these forest ecosystems.
If you have woods on your property, there are essentially three management options: resistance, resilience, and transition. Removing invasive species such as reed canary grass, buckthorn, and garlic mustard helps to protect native woodland plant communities. Forests and woods are also more resistant to pests and invasive species if there are fewer land disturbances such as roads, trails, and construction projects nearby. You may also want to consider the climate change vulnerability of tree species when deciding what to plant on your property. Species that are expected to be more resilient to change include bur oak, hazelnut, redosier dogwood, serviceberry (Juneberry), and hawthorn. Another strategy is to plant trees that are expected to move into Minnesota over the next 100 years. Examples include American beech, black locust, chinkapin oak, pin oak, sassafras, scarlet oak, and shagbark hickory.
The Minnesota DNR offers cost-share grants to woodland land owners for a variety of projects including reforestation and tree planting, removing invasive species, planting a native prairie to improve habitat, or developing a woodland stewardship plan. There is no minimum acreage required to apply for grants, though you must have at least 20 acres to get support for a woodland management plan. Funds are available until June 30, 2019. Learn more at: www.dnr.state.mn.us/woodlands/cost-share.html or contact Andy McGuire at Andy.McGuire@state.mn.us.
You can also find a large collection of woodland management resources, including contact information for local service providers at www.mystcroixwoods.org.