URBANA, Ill. — Frequent prescribed burns in southern Illinois forests are improving young oak survival despite invasive grasses, researchers found.
According to a University of Illinois Urbana-Champaign study published in March, repeated controlled burns in oak-hickory forests increased light availability and reduced invasive grass presence, creating better conditions for oak regeneration.
Researchers, led by Professor Jennifer M. Fraterrigo, studied forest plots in the Shawnee National Forest and found that nearly twice as many young oak trees survived and resprouted in areas burned multiple times compared to areas burned only once. The study focused on the effects of invasive species such as Microstegium vimineum, commonly known as stiltgrass, which can suppress native plant growth.
Fraterrigo said land managers had been concerned that invasive grasses could worsen fire intensity and harm young trees. However, the findings suggest that more frequent burns may counteract those risks by reducing understory competition and limiting invasive spread.
The study also found that repeated burns decreased stiltgrass cover, helping restore conditions favorable to native oak ecosystems. Illinois’ oak-hickory forests depend on periodic fire to clear debris and open the canopy, allowing sunlight to reach the forest floor.
Co-author Dan Marshalla noted that the results support prescribed fire as a long-term management strategy, though additional research is needed to understand how invasive grasses respond over time.
The research was conducted with assistance from University of Illinois Extension forestry programs and supported in part by federal funding.
The findings may influence land management practices across Illinois, particularly in areas where invasive species threaten forest regeneration. The results are also relevant to students and early-career environmental workers studying conservation and forestry practices.
