Invasive plants like cheatgrass are expanding in Western rangelands, speeding up the fire cycle in the sagebrush steppe, along with climate change, and threatening the most widespread ecosystem in the country.
But much more research has been done to evaluate wildfire mitigation tools in forests.
With funding from the Bureau of Land Management and the National Interagency Fire Center, a handful of researchers from universities in Oregon, Nevada, Idaho, Montana and Utah teamed up to study different strategies to reduce fire intensity on the sagebrush landscape over the course of a decade.
The researchers looked at six sagebrush sites where annual invasive grasses like cheatgrass have also crept in.
They tested out prescribed fire, mechanical thinning, an herbicide and a control to see how they measured up according to a couple of goals.
“One is to reduce the fire behavior, so make it easier for firefighters to stop the fire,” said Dr. Eva Strand, an associate professor of rangeland ecology at the University of Idaho, who was an author of the study.
The other variable was the overall health of the habitat – for example, how sagebrush grew back over the course of the decade compared to invasive plants.
At several intervals, the researchers measured the vegetation in the different plots. They used those results to create fire behavior models that showed how quickly a fire would spread across a given landscape and how high the flames might be.
The results, published in the journal Ecosphere this month, showed burning and thinning reduced the overall amount of combustible vegetation, even through the 10-year mark, but the herbicide did not.
Another takeaway, according to Strand, was that while prescribed fire is a healthy management tool in forests, that’s not always the case in the sagebrush ecosystem.
“In an area where you have a lot of annual grasses to begin with, you probably wouldn't want to do a prescribed fire treatment,” she said.
That’s because the burns can make the cheatgrass problem worse, which can in turn speed up the fire cycle. But, this method works better in sagebrush at higher elevations.
Strand is also leading research evaluating fuel breaks used slow down fire in southern Idaho.
Find reporter Rachel Cohen on Twitter @racheld_cohen
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