Research featured in the latest edition of the journal Invasive Plant Science and Management shows that the weed downy brome has developed fire-survival traits that are changing local growing conditions and making it impossible for native competitors to survive.

Downy brome has invaded millions of acres of arid grasslands in the western U.S. As a winter annual, it finishes its life cycle by spring or early summer — several weeks before native grass species. The dried downy brome offers a large horizontal mass that can fuel frequent fires and help them quickly spread.

Researchers in the U.S. and Europe compared downy brome from the fire-prevalent U.S. Great Basin with populations of downy brome in Central Europe, where fires are rarely experienced. They discovered that U.S. populations of the weed produce seeds with a greater fire tolerance. The seedlings perform better in post-fire environments, produce more above-ground tissue and are more flammable than populations of downy brome in Central Europe.

“The increased flammability of downy brome in the U.S. and its greater aboveground plant mass promote earlier, more frequent fires of low intensity,” says Annamária Fenesi, a senior lecturer at Babeş-Bolyai University in Romania. “While downy brome thrives under those conditions, native species that have adapted to a much longer interval between fires are simply unable to recover. As a result, downy brome is able to thrive and spread, free of competition.”

Full text of the article “Enhanced Fire-Related Traits May Contribute to the Invasiveness of Downy Brome (Bromus tectorum)” is available in Volume 9, Issue 3 of the journal Invasive Plant Science and Management.