Barrens are an important aspect of the environment, and MSU's Jessica Miesel is helping improve methods to restore them through burning.
February 14, 2017 - Author: James Dau
The savanna, while iconic of the central Africa landscape, is also prevalent in many regions across the United States from New England through the Upper Midwest. Open, savanna-like ecosystems have long relied on periodic, naturally occurring fires to void them of large tree species that increase shade, stave off shrubs and grasses, and lead to succession — a process of transforming open spaces into forests.
Such drastic environmental changes alter the habitat available to wildlife, sending ripples through the entire ecological system. The process of succession has recently threatened open landscapes in Wisconsin, where savnna-like ecosystems called barrens were once quite prevalent.
Barrens environs lack the soil nutrients to support the robust forestland for which much of the Eastern United States is known, but occupy a critical role as home to a number of ecologically significant species of flora and fauna. Recent estimates from the University of Wisconsin, Madison, show that barrens in the state have been reduced to 1 percent of their original area, and that reduction threatens the survival of species such as the sharp-tailed grouse and frosted elfin butterfly.
Working alongside U.S. Forest Service fire managers at the Chequamegon- Nicolet National Forest in northern Wisconsin, who are currently undertaking major barrens-restoration projects, Michigan State University (MSU) AgBioResearch forest ecologist Jessica Miesel is helping improve methods to restore barrens.
“Barrens are considered globally important,” said Miesel, an assistant professor in the MSU Department of Forestry. “They’re a very rare environment that many plant and animal species depend on, and they’re disappearing.”
As the importance of fire in both woodland and barrens ecosystems has become more apparent, prescribed, burns have emerged as a common tool for forest managers. Miesel’s team is in the middle of a three-year project to provide managers with more information on the impact of fire on various aspects of the environment, including the soil.
Miesel co-leads this portion of the project with a U.S. Forest Service colleague. Any observer will note that fire effectively destroys much of the aboveground vegetation. The challenge lies in the fact that plants significant to the process of forest succession, such as oak trees, sprout anew from subterranean roots left untouched by the inferno above. Miesel’s team is studying the conduction and impact of heat on soil.
“Soil doesn’t conduct heat very well, so even though we get extremely high temperatures aboveground, the soil temperature can stay relatively low,” Miesel said. “We need to measure soil heating because being able to kill the oak root systems depends on being able to raise that temperature.”
To study soil heating, Miesel’s team embedded a series of thermocouples — pairs of conductive wires made of different metals connected at both ends — at a range of depths in the soil prior to U.S. Forest Service-controlled burns. These sensors relay information to remote data-logging equipment that records soil temperature over the course of the blaze.
In addition, the team hung aluminum tags coated in temperature-sensitive paint at elevations between zero and 25 centimeters above the ground to complete the picture of heat transfer during a forest fire. Though the pervasion of heat through soil is important, so, too, is that heat’s impact on essential soil processes.
To understand the impact of forest fires on the soil’s ability to mineralize nitrogen, one of the most critical nutrients for sustaining any form of plant life, the team inserted ion exchange probes in the soil and collected coil samples to help determine how quickly nutrients are cycled in and restored compared to unburned areas.
“Fire can affect the soil microbial community,” Miesel said. “Measuring nitrogen mineralization rates lets us know how the ecosystem is functioning before and after the fire has taken place.”
Though Miesel’s work is not yet complete, numerous observations are starting to emerge from the data. On many occasions, the aluminum tags melted, which happens at over 660 degree Celsius — well above the expected temperature — while the thermocouples continued to report extremely low soil temperatures.
Miesel’s team hypothesizes that this could be due to high soil moisture levels in spring, when controlled burns are normally undertaken, and that adjusting the burn schedule to the summer, when fires would naturally occur, could be more effective in restoring the barrens. Miesel’s experience with forest fires, stretching back to her work on fire suppression details at Rocky Mountain National Park in northern Colorado and extending through research ever since, has shown their power.
“I’ve always found it a fascinating process, and so many ecosystems depend on it to maintain their vegetation composition and structure,” she said. “We don’t usually see fire as a creative force, but that’s exactly what it’s doing here. It’s creating habitats.”