Urbana, Ill., April 3: New research from the University of Illinois Urbana-Champaign reveals that frequent prescribed burns in forests affected by invasive grasses can significantly improve the survival and growth of young oak trees, offering renewed confidence for land managers working to restore oak-dominated ecosystems.
The study, published in the Journal of Applied Ecology, examines how repeated fire treatments influence forest dynamics in Midwestern oak-hickory ecosystems, particularly in areas impacted by invasive species such as stiltgrass.
Led by Jennifer M. Fraterrigo, professor in the Department of Natural Resources and Environmental Sciences, the research addresses a growing concern among land managers that invasive grasses could intensify fires and hinder oak regeneration.
“This was a real problem for land managers,” said Fraterrigo. “Prescribed fire is one of the most effective tools for managing large forest areas. If fire had unintended negative effects, it would make it difficult to achieve restoration goals.”
Balancing Fire and Invasive Species
Native oak-hickory forests in regions such as the Shawnee National Forest are naturally adapted to fire. Controlled burns help remove underbrush, open the canopy, and allow sunlight to reach the forest floor—conditions essential for acorn germination and oak growth.
However, the spread of invasive grasses like Microstegium vimineum has raised concerns. These grasses can increase fuel loads, potentially leading to hotter fires and creating a feedback loop that favors invasive species over native plants.
Key Findings
Through controlled burns conducted across multiple forest plots, researchers found that:
- Frequent prescribed fires increased light availability in the forest understory
- Fire intensity decreased with repeated burns
- Nearly twice as many young oak trees survived and resprouted in frequently burned areas compared to those burned only once
- Invasive stiltgrass coverage declined with increased fire frequency
“Our findings show that sustained, repeated fire over time is key to achieving desired outcomes in forest restoration,” Fraterrigo noted.
Co-author Dan Marshalla added, “These results should give land managers greater confidence in using prescribed fire, even in forests where invasive grasses are present.”
Supporting Sustainable Forest Management
The study also involved collaboration with forestry experts, including Chris Evans, who emphasized the practical implications of the findings.
“The research supports prescribed fire as an effective management tool, particularly for promoting oak regeneration,” Evans said. “What stands out is how repeated burns can mitigate some of the negative impacts of invasive species.”
Funded in part by the U.S. Forest Service and the USDA National Institute of Food and Agriculture, the study highlights the importance of long-term strategies in ecosystem management.
Looking Ahead
As climate change and invasive species continue to reshape forest ecosystems, the findings underscore the value of adaptive, science-based land management practices. By demonstrating that repeated prescribed burns can restore balance in affected forests, the research offers a pathway toward healthier, more resilient oak ecosystems.
