Seeding causes long-term increases in grass forage production in invaded rangelands

Authors: Rinella, Matthew - Matt; KNUDSEN, ALAN - Retired Non ARS Employee; JACOBS, JAMES - Retired Non ARS Employee; MANGOLD, JANE - Montana State University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2019
Publication Date: 11/6/2019
Citation: Rinella, M.J., Knudsen, A., Jacobs, J.S., Mangold, J.M. 2019. Seeding causes long-term increases in grass forage production in invaded rangelands. Rangeland Ecology and Management. 73(2):329-333. https://doi.org/10.1016/j.rama.2019.10.008.
DOI: https://doi.org/10.1016/j.rama.2019.10.008

Interpretive Summary: Seeding has long been considered an option for increasing grass forage production in invaded rangelands, but the lack of long-term data prevents determining if seeded grasses have a reasonable chance of becoming and staying productive enough to justify this expensive practice. We quantified long-term seeding outcomes in a widespread Rocky Mountain foothill habitat invaded by leafy spurge and several exotic grasses. Fourteen years after seeding five grasses into separate plots of a replicated experiment, all seeded grasses persisted, and the most productive grass, bluebunch wheatgrass, produced about 70% of total plant community biomass. This result was not fundamentally altered by grazing according to an un-replicated, grazed experiment adjacent to our replicated un-grazed experiment. Bluebunch wheatgrass reduced exotic grasses about 85%, but no seeded grass reduced leafy spurge, though leafy spurge became less productive over time. Our results resemble those of a previous long-term study in foothills invaded by a functionally much different weed, spotted knapweed, so seeding outcomes seem insensitive to invader composition. Our results also mirror those of a long-term study in leafy spurge-invaded Great Plains habitats, so seeding can reverse forage losses across much of the leafy spurge invasive range. While there is always a risk seeded grasses will fail to persist in invaded rangelands, there is a good possibility seeded grasses will form persistent, productive stands in leafy spurge-invaded rangelands and invaded Rocky Mountain foothills rangelands.

Technical Abstract: Seeding has long been considered an option for increasing grass forage production in invaded rangelands, but the lack of long-term data prevents determining if seeded grasses have a reasonable chance of becoming and staying productive enough to justify this expensive practice. We quantified long-term seeding outcomes in a widespread Rocky Mountain foothill habitat invaded by leafy spurge (Euphorbia esula L.) and several exotic grasses. Fourteen years after seeding five grasses into separate plots of a replicated experiment, all seeded grasses persisted, and the most productive grass, bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) Á. Löve), produced 90(10, 1200) g m-2 [mean(95% CI)], or about 70% of total plant community biomass. This result was not fundamentally altered by grazing according to an un-replicated, grazed experiment adjacent to our replicated un-grazed experiment. Pseudoroegneria spicata reduced exotic grasses about 85%, but no seeded grass reduced E. esula, though E. esula became less productive over time. Our results resemble those of a previous long-term study in foothills invaded by a functionally much different weed, spotted knapweed (Centaurea stoebe L. ssp. micranthos (Gugler) Hayek), so seeding outcomes seem insensitive to invader composition. Our results also mirror those of a long-term study in E. esula-invaded Great Plains habitats, so seeding can reverse forage losses across much of E. esula’s invasive range. While there is always a risk seeded grasses will fail to persist in invaded rangelands, there is a good possibility seeded grasses will form persistent, productive stands in E. esula-invaded rangelands and invaded Rocky Mountain foothills rangelands.