Prescribed Burns Boost Young Oaks Amid Invasive Grasses

Study finds frequent fires reduce invasive stiltgrass and promote oak regeneration in Midwestern forests.

Apr. 3, 2026 at 7:08am

Got story updates? Submit your updates here. ›

A highly textured, abstract painting in earthy tones of green, brown, and ochre, depicting the complex interplay of geometric shapes, botanical spirals, and concentric circles to represent the natural forces at work in a forest ecosystem undergoing prescribed burns to promote oak tree growth amid invasive grasses.Prescribed burns help young oak trees thrive by disrupting the cycle of invasive grasses in Midwestern forests.Urbana Today

A new University of Illinois study found that conducting more frequent prescribed burns in forests with invasive grasses like stiltgrass creates conditions that benefit young oak tree growth. The research showed that almost twice as many young oak trees survived and resprouted in plots that had been burned more often, as the fires reduced the intensity and spread of the invasive grasses.

Why it matters

Oak-hickory forests are a crucial part of the Midwestern ecosystem, but the introduction of non-native grasses like stiltgrass has made it challenging for land managers to use prescribed burns effectively to promote oak regeneration. This study provides evidence that more frequent controlled burns can overcome the negative impacts of invasive grasses, helping to preserve and restore these important forest habitats.

The details

The researchers applied controlled burns in plots with young oak trees in the Shawnee National Forest in southern Illinois. They found that frequent fires increased light in the forest understory and reduced fire intensity, allowing almost twice as many young oak trees to survive and regrow compared to plots with only a single burn. Stiltgrass cover also decreased with more frequent fires.

  • The study was conducted in the Shawnee National Forest in southern Illinois.
  • The researchers applied controlled burns in the forest plots during prescribed burn season, as winter came to a close.

The players

Jennifer M. Fraterrigo

A professor at the University of Illinois Urbana-Champaign who studies how ecosystems respond to environmental change, including the effects of fire and disease.

Dan Marshalla

A former graduate student in the Department of Natural Resources and Environmental Sciences at the University of Illinois, who led much of the data collection and analysis for the study.

Chris Evans

A Forestry Extension and Research Specialist at the University of Illinois who supported the field research for the study.

Shawnee National Forest

A national forest located in southern Illinois where the researchers conducted the controlled burn experiments.

Got photos? Submit your photos here. ›

What they’re saying

“This was a real problem for land managers. Prescribed fire is the most effective tool they have to manage large areas. If fire is having this unexpected, potentially adverse effect, it would be difficult for them to achieve their management objectives.”

— Jennifer M. Fraterrigo, Professor

“Our findings of the benefits of repeated fire for oak regeneration should boost the confidence of land managers who want to use prescribed fire to promote oaks but are wary about the presence of stiltgrass.”

— Dan Marshalla, Graduate Student

“The study supports the use of prescribed fire as a management practice for forests in Illinois, especially as a means to promote oak regeneration. The most interesting aspect was how repeated fire seemed to mitigate some of the negative impacts of stiltgrass.”

— Chris Evans, Forestry Extension and Research Specialist

What’s next

The researchers noted that further study is needed to understand the full effect of repeated fire throughout the life cycle of invasive stiltgrass, in order to provide more comprehensive guidance to land managers on the optimal prescribed burn strategies for promoting oak regeneration in forests with invasive grasses.

The takeaway

This study demonstrates that frequent, repeated prescribed burns can be an effective tool for land managers to overcome the challenges posed by invasive grasses like stiltgrass and promote the regeneration of valuable oak trees in Midwestern forests. The findings should give managers more confidence in using fire as a management practice to preserve and restore these important ecosystems.