Controlled burns are used to prevent larger, uncontrollable wildfires, and as a strategy for promoting biodiversity and regenerative growth in deciduous forests. But new research suggests the practice also encourages an aggressive species of invasive grass.

The grass in question is Microstegium vimineum, sometimes called Japanese stiltgrass or Nepalese browntop. A native of Asia, the low-light annual is now found in 26 U.S. states, mostly in the Southeast. It's also found in southern Illinois, where researchers observed its invasion of recently burned forest.

The grass is particularly adept at invading roadsides, floodplains and disturbed habitats. A University of Illinois study found controlled burning to be an especially attractive disturbance to invading stiltgrass.

At burn sites with typically wet conditions, that grass increased its biomass by 214 percent. In drier, recently-burned environs, the grass was not as prolific, increasing its biomass by 135 percent.

"M. vimineum can produce a dense carpet of growth that shades out tree seedlings and other resident plants," Jennifer Fraterrigo, Illinois University ecologist, said in a press release. "It also competes well for nitrogen, thereby limiting the amount available of this nutrient to other species. Unfortunately, there do not appear to be many herbivores that eat this particular grass. So once it is established, it can be difficult to eradicate."

Fraterrigo understands that burning can't and won't stop entirely, but she hopes her work can better educate land managers and others as to the risks.

As researchers detailed in the journal Forest Ecology and Management, burning in wet environs within the vicinity of a stiltgrass seed source leaves a forest especially vulnerable. Still, fire is vital to a variety of vulnerable plant and animal species.

"Fire is one of the best management tools that land managers have at their disposal so we can't expect managers not to burn at all," Fraterrigo said. "Several rare native plant species thrive following controlled burning, which reduces dominant competitors. If we stop burning, those species may disappear."

Fraterrigo hopes her and her colleagues' work, however, can help land managers make smarter choices about when and where to employ burns. She also hopes conservationists can find new techniques for securing the advantages of controlled burns while limiting the risk of stiltgrass invasion.