Spring Seeding Integrated with a Spring Glyphosate Application Promotes Establishment ofPseudoroegneria spicata(bluebunch wheatgrass) inBromus tectorum(cheatgrass)-infested Rangelands

Abstract

Bromus tectorum invasion and associated impacts have been documented extensively in the western United States. Integrated approaches have been shown to be effective in restoring rangeland impacted by B. tectorum. While integrating herbicide and seeding of native species can be effective, strategic timing of these tools could further improve restoration outcomes. At three B. tectorum-infested rangeland sites in western Montana, we tested the effects of glyphosate application and timing (fall or spring) and five Pseudoroegneria spicata seeding dates (one fall and four spring dates) on density and cover of P. spicata. Pseudoroegneria spicata density was nearly ten times higher with glyphosate applied to B. tectorum compared to none at one site, and P. spicata abundance was generally greater when spring glyphosate application was combined with spring seeding at two other sites where densities ranged from six to 25 plants per m2. Overall, B. tectorum abundance was minimally affected by treatments and fluctuated between years and across study sites. Our results indicate that spring seeding of P. spicata following a spring glyphosate application promoted establishment of P. spicata, increasing its density and cover compared to fall glyphosate application and fall seeding, spring glyphosate following fall seeding, or seeding without any glyphosate. Restoration practitioners have an ecologically-based strategy for timing glyphosate application and seeding P. spicata based on our results, where spring-seeded P. spicata can grow for several months prior to fall emergence of the next B. tectorum cohort.