Throughout Minnesota's forests, the invasive shrub common buckthorn poses serious threats to forest health and ecosystem function. This fast-spreading invader crowds out native plants and can quickly take over woodland spaces, making it a top target for land managers and restoration crews across the state.
Cutting down buckthorn often fails to provide a permanent solution. When given sufficient sunlight and space, it can rapidly recover and re-establish itself in the same location within just a few years.
However, researchers at the University of Minnesota have found a clever way to tip the odds against this woody invader. Their findings were recently published in Restoration Ecology.
Funding for this research was provided by the University of Minnesota's Minnesota Invasive Terrestrial Plants and Pests Center, supported by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources.
Past studies show that scattering seeds of native grasses and wildflowers right after buckthorn is removed can help keep buckthorn from coming back. The native plants compete for sunlight and nutrients alongside buckthorn seedlings, making it harder for young buckthorn to gain a foothold. This management strategy, called revegetation seeding, has shown promising results in small experimental plots.
To see whether revegetation could help forests across the state, University of Minnesota researchers teamed up with science volunteers to try the technique in woodlands throughout Minnesota.
The study found:
- Buckthorn seedlings were about 45% smaller in places where volunteers seeded native grasses and wildflowers compared to buckthorn seedlings in plots that weren't seeded.
- Revegetation seeding provided a significant increase in native vegetative cover compared to plots that weren't seeded.
- Cover by grasses and sedges, rather than forbs, contributed most to buckthorn suppression within revegetation seeded plots, suggesting that grasses like Canada Wildrye are well-suited to suppress buckthorn throughout much of the state.
- Buckthorn removal and revegetation of native species can be successfully carried out by stakeholders throughout the state without specialized training to equipment.
"This study helps us to better understand the role that everyday people can play in on-the-ground forest restoration regardless of skill level or formal ecological knowledge," said Mark Fuka, co-author of the study and a plant community ecologist in the in the University of Minnesota College of Food, Agricultural and Natural Resource Sciences.
"We've shown how native plants like Canada Wildrye can help suppress buckthorn in our earlier works, but this study takes a big leap forward," said Mike Schuster, co-author of the study and a researcher in the University of Minnesota College of Food, Agricultural and Natural Resource Sciences. "Not only did we find that seeding native grasses and wildflowers helped keep buckthorn out of Minnesota woodlands, we found that that was true across a huge diversity of site conditions and more than 100 different practitioners. This is a winning strategy that almost anyone can use."
According to the study's authors, the results suggest that revegetation seeding can work at a large scale to help keep buckthorn in check. For land managers hoping to try the approach, the most effective seed mixes appear to be those rich in native grasses and sedges, which quickly fill in the space and compete with young buckthorn seedlings.
As for next steps, the research team is now looking ahead to what these restored forests might become over time. Important questions remain regarding the many other impacts revegetation might have on forests, ranging from improving habitat for pollinators to helping woodlands recover from fungal pathogens. The researchers are optimistic that this approach will provide many diverse benefits to the forests of Minnesota and beyond.
"Although we often focus on the largest buckthorn during removal efforts, it's generally the little buckthorn that trip up restoration efforts," said Schuster. "Without further intervention, those little plants grow up fast and easily replace their felled relatives; this work shows that we can reliably shut those little plants out by reseeding native species in many of Minnesota's broadleaf forests."
About the College of Food, Agricultural and Natural Resource Sciences
The University of Minnesota's College of Food, Agricultural and Natural Resource Sciences strives to inspire minds, nourish people, and sustainably enhance the natural environment. CFANS has a legacy of innovation, bringing discoveries to life through science and educating the next generation of leaders. Every day, students, faculty, and researchers use science to address the grand challenges of the world today and in the future. CFANS offers an unparalleled expanse of experiential learning opportunities for students and the community, with 12 academic departments, 10 research and outreach centers across the state, the Minnesota Landscape Arboretum, the Bell Museum, and dozens of interdisciplinary centers. Learn more at cfans.umn.edu.
About the Minnesota Invasive Terrestrial Plants and Pests Center
The Minnesota Invasive Terrestrial Plants and Pests Center was founded by the Minnesota Legislature to research the prevention, detection and control of terrestrial invasive species. MITPPC researchers use transformative science to prevent and minimize the threats posed by land-based invasive plants, pathogens, and pests. Founded in 2015, MITPPC is the only research center of its kind in the country, and the center's work to protect the state's native prairies, forests, wetlands, and agricultural resources benefits all of Minnesota and beyond. MITPPC receives program support from the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources. Learn more at mitppc.umn.edu.
