Bison in the Cedar Creek oak savannah.

MN Impact: Researchers explore the interwoven roles of fire and wildlife in oak savanna conservation by introducing bison

May 27, 2020

Issue

In the Midwest, oak savannas were once abundant—in Minnesota alone they once accounted for 10 percent of the native vegetation. However, as a fire dependent ecosystem, oak savannas have been significantly reduced by farming and development. Today, intact oak savannas are one of the rarest ecosystems on earth.

What has been done

Each spring, the fire team at the Cedar Creek Ecosystem Science Reserve conducts prescribed burns at locations around the station totaling over 900 acres. This annual effort is part of a long-term research experiment to better understand the role of fire in maintaining prairie and oak savannas.

One downside of the burns has been the killing of young oak trees, which cannot survive the hot and intense fires. Researchers at Cedar Creek were interested in exploring the role traditional wildlife may have played in helping protect the oaks that play an integral role within the ecosystem by providing shelter to wildlife. Starting in 2018, they introduced bison, hoping that bison grazing the native prairie grass would reduce the intensity of the fires—thus sparing the young oaks and giving them time to mature.

Results

Beyond their popularity with the public, areas grazed by the bison have been 180°C cooler during the burns. In addition, areas grazed by bison have shown very high survivorship among young oak seedlings.

Cedar Creek has been practicing prescribed burning since the 1960s, making it one of the longest ongoing scientific fire experiments in the world. Throughout this time, they have learned invaluable information about the role fire plays in nutrient cycling, ecosystem health, and the restoration and maintenance of rare landscapes. And now, they are adding to this, the exploration of the role native wildlife plays in balancing these fragile systems.