Sergio Arispe

OSU’s Sergio Arispe 

Researchers and southeastern Oregon ranchers aim to determine if large-scale dormant-season grazing can knock out substantial amounts of invasive annual grasses and reduce rangeland fire risk.

In a 25,000-acre study area east of Owyhee Reservoir, cattle numbers traditionally are reduced before Nov. 1 — right around the time perennial grasses go dormant and temperatures become nearly perfect for germination of invasive cheatgrass and medusahead, Oregon State University Extension rangeland and livestock specialist Sergio Arispe said.

These annual invasive grasses, which grow before native bunch grasses and compete for water and other resources, can form a mat-like litter on the ground.

“It is that litter, the old growth, which protects that (invasive) seed and increases biomass, flammable material and fuel,” the Ontario, Ore.-based Arispe said. “If we can disrupt that litter using dormant-season grazing, we can expose that seed to the elements, extreme cold temperatures and rodents. It’s going to be less likely to germinate.”

USDA’s National Institute of Food and Agriculture is funding the three-year, $300,000 study through 2022. It involves the U.S. Bureau of Land Management Vale District and researchers from OSU, the University of Idaho, Boise State University and the University of Nevada-Reno.

Ranchers on the greater Three Fingers Allotment are participating. Ranchers, wary of big fires cutting the number of permits available, expressed interest to the BLM in finding an unconventional method to reduce fire risk. The allotment includes sage grouse habitat, wilderness study areas, recreation destinations and archeological sites as well as invasive grasses.

Vale District BLM is allowing Arispe to recruit ranchers, who so far have committed up to 1,700 cows to graze in dormant season, he said. Grazing is slated from mid-October through February.

Vale District BLM Manager Don Gonzalez said grazing permits generally cover the spring-fall season, “so because it’s an experiment, we authorize grazing though a different authorization.”

For the study period, “we will review it each year to see if what we are doing needs to be adjusted and if the rancher is still willing to participate” in subsequent years, he said.

“The hypothesis is that we can promote rangeland health so that the sagebrush steppe ecosystem can be more resistant to invasive annual grasses and resilient to disturbances such as fire,” Arispe said.

Cattle in late fall are pregnant and have elevated nutrition requirements, he said. Available range grass is brown and short on protein and energy.

“In order to meet those nutritional requirements, we are supplementing protein — which helps them digest, meet the nutrient requirement and eat more of the dead material,” Arise said.

OSU and USDA Agricultural Research Service staff in Burns have studied sagebrush ecosystem health and early grazing. He said a handful of research papers on dormant-season grazing have been published, but the current effort is large-scale and focuses on the Interior West.

It will track plant-community characteristics on a landscape scale using satellite imagery and other technology, and make information available for land-management planning and educational uses, Arise said.

“We will be teaching rangeland managers about the science-based framework to assess rangeland health, and also to develop land management plans” using online and geographic information system tools, he said.

Researchers want at least 75% of participants to learn rangeland ecology basics, improve their knowledge of ecological outcomes related to dormant-season grazing, and learn applied uses for remote sensing technologies in managing fine-fuels, an abstract said.

Field days are planned Oct. 4 at Rockville, Ore., off U.S. 95 and Oct. 17 at Burns District BLM. Dormant-season grazing will be highlighted at the UI Rangeland Fall Forum in Marsing, Idaho, Oct. 10-11.

Recommended for you