Thinning sagebrush: Projects enhance wildlife habitat, grass for livestockWritten by Jennifer Womack
Whitson has spent considerable time researching the thinning of sagebrush using a Dow Agrosciences’ product called Spike 20P. With an active ingredient of tebuthiuron, varying rates of the herbicide sold in pellet form are used depending on soil type and organic matter content in a given area. In sandier soils, application rates might be half a pound per acre varying up to 2.5 pounds per acre in heavier soils where organic matter binds with the product.
Aerial application costs begin in the $4.00 per acre range. In the Rawlins district of the BLM, the agency has partnered with permit holders. Ranchers pay for the flying and application while the agency covers the cost of the Spike 20P.
From 1880 to the passage of the Taylor Grazing Act in 1934 Whitson says overgrazing resulted in larger than normal sagebrush plants. Of “relic sites” that haven’t been grazed by wildlife or livestock, he says the sagebrush plants are smaller with a 12-15 percent live canopy cover. With the thinning projects, many of which take places in areas where the live canopy cover of sagebrush has reached 25-36 percent he says, “We get a chance to start over.” The length of the projects’ effectiveness is dependent upon management and grazing after the project’s completion.
Spike, with a half-life of 360 days, provides about two years of control against sagebrush seedlings. During that time, Whitson says what was the understory begins to fill in the areas between remaining sagebrush plants. An analysis of understory is important prior to carrying out treatment.
Depending on the surrounding vegetation, removal of sagebrush can allow annuals or undesirable plants to expand. “It doesn’t affect rabbit brush and it doesn’t affect cheat grass,” explains Whitson. “If we have an area with cheat grass we may just release more cheat grass if it doesn’t have good perennial grass understory. We’ve got to really plan and target. You can’t have something that doesn’t have any understory.”
On the first stop of the day, rhizomatous western wheatgrass was filling the voids created by the reduction in sagebrush. The presence of forbs also increased. No seeding was carried out, but an alteration that enhanced the grasses’ competitiveness and presence. Whitson says projects such as this are a great economic stimulus opportunity as one acre is now producing what used to take nine acres. He further explains that one unit of water will produce five times more grass than sagebrush.
Whitson boils the benefits down to a numeric value. “If we figure hay prices at $40 to $60 per ton, that would be two to three cents per pound for the grass. We’ve got 900 pounds of grass per acre here. If you take half and leave half, there would be at least $15 worth of grass here for the livestock. We’re getting this for 30 years, 40 years, who knows. It depends on if they overgraze it to a point where they let sagebrush dominate again.”
“We create a diversity,” says Whitson of the benefits to wildlife. “Because of the thinning approach we have good nesting habitat for the sage grouse.”
“When we do burns we’re typically looking at 10 years of recovery before there’s enough cover that sage grouse are going to use it to any extent. In some cases it’s longer,” says Andy Warren who oversees the range management program at the BLM in Rawlins. “With Spike you’re doing a thinning. You’re reducing it from say, 35 to 40 percent cover, down into the range the grouse want within a few years. You’re not taking it out of use for any length of time.” There are areas where burning is a preferred approach and it’s a tool the agency continues to use.
Whitson says, “We have antelope habitat. Normally in the fall these sagebrush plume will get taller because there’s less of them. The antelope eat that plumes in the wintertime because it sticks up above the snow.”