Researchers study how grazing on invasive grasses can affect wildfire threat

A stretch of raw land near Ironside in Malheur County. (The Enterprise/Rachel Parsons)

A research project by Oregon State University’s Extension Service in Malheur County is examining whether grazing on invasive grasses can help mitigate wildfire threats in the sagebrush steppe.

The goals behind the study are to improve rangeland health and to reduce fine fuels in the ecosystem, said Sergio Arispe, livestock and rangeland field faculty with OSU’s Extension Service in Malheur County. 

Fine fuels are invasive annual grasses that aren’t native to the sagebrush steppe ecosystem, he said. Depending on precipitation and soil type, the native vegetation can range widely from 350 to 1,200 pounds per acre in the sagebrush steppe.

Fine fuels can add 2,000-3,000 pounds per acre and “when fire comes, that provides a lot of fuel that can ignite and carry a very hot and fast wildfire,” he said.

Arispe said fine fuels are the greatest threat to rangeland health at lower elevations in the sagebrush steppe.

“The sagebrush ecosystem is one of the most endangered ecosystems in America due to multiple threats, including non-native annual grass invasion and increased frequency and size of wildfires,” according to a project summary for the study.

Large wildfires can lead to dramatic spread of invasive grasses, the summary said.

The Eastern Oregon Agricultural Research Center in Burns developed a threat-based framework for land managers to identify the ecological state of a sagebrush steppe ecosystem, Arispe said. He hopes to teach others through the research project how to use the tool, he said, as well as find out if grazing on public lands in the winter can improve the range health and reduce wildfires.

As part of the study, researchers at the extension service have found up to 8,000 pounds of grasses per acre in some areas on public lands, he said.

With fires destroying native vegetation and fine fuel seeds facing little competition, such range fires are becoming more frequent. If the native plants are wiped out, he said, it can lead to an environment dominated by fine fuels, “which perpetuates the grass-fire cycle.”

“The grass-fire cycle is the phenomenon on rangelands whereby fire burns vegetation on the sagebrush steppe and invasive annual grasses invade the burned areas,” he said. “Those grasses build up vegetative fuel that readily burns when ignited by a fire source.”

After the 2015 Soda Fire and 2016 Cherry Road fire burned around 250,000 and 26,000 acres, respectively, the Vale District Bureau of Land Management and local ranchers approached Arispe “about the possibilities of looking into how to mitigate wildfires at the landscape levels,” he said.

The federally funded study began in 2018 and is projected to last ten years, he said.

Though Arispe said he can’t yet answer whether grazing can mitigate wildfires, he expects to have the first round of data next summer.

The researchers are measuring vegetation, clipping it, putting it into bags and drying it before determining how much fuel is on the landscape, he said.

They are also collaborating with Nancy Glenn, a geosciences professor at Boise State University, to combine plant measurements from their 30-acre sample with satellite imagery to create a model of the larger 23,000-acre landscape, he said.

Helping with the project are the University of Idaho Extension Service, University of Nevada-Reno and University of Nevada Cooperative Extension.

News tip? Contact reporter Ardeshir Tabrizian by email at [email protected] or call 503-929-3053.


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