Authors: Raechel Hunsaker, Matthew Madsen, Mallory Hinton, Derek Tilley, April Hulet
Mentors: April Hulet
Insitution: Brigham Young University
Many early successional plant species have been considered weeds because of their lack of forage value for livestock. However, early successional plant species have the potential to aid rangeland restoration by providing food sources for pollinators, modifying soil in preparation for climax plant communities, and competing against invasive species. To determine which early colonizing species have the greatest restoration potential, interspecific competitive interactions should be evaluated. Our research objective was to evaluate the competitive abilities of two native pioneer forb species, curlycup gumweed (Grindelia squarrosa) and prairie aster (Machaeranthera tanacetifolia), against three common rangeland grasses including 1) native early successional species, bottlebrush squirreltail (Elymus elymoides), 2) invasive colonizing species, cheatgrass (Bromus tectorum), and 3) climax community species, bluebunch wheatgrass (Pseudoroegneria spicata). Treatments included each of the three grass species seeded at high and low densities with curlycup gumweed or prairie aster in two soils (mine tailings and disturbed rangeland) in a greenhouse. After being cultivated for 54 days, above-ground biomass for both forbs were not significantly different when seeded alone, or with high and low densities of grasses in the mine tailings soil (p ≥ 0.05). However, in soil from the disturbed rangeland, forb biomass differed. When planted alone, curlycup gumweed and prairie aster biomass was on average 2.5- and 3-fold greater than when planted with high and low densities of squirreltail and cheatgrass (p ≤ 0.05). Both forbs had significantly lower biomass when planted with a high density of bluebunch (p ≤ 0.05), however, when planted with a low density of bluebunch, biomass was not significantly different than when planted alone (p ≥ 0.05). Results indicate that high densities of squirreltail, cheatgrass, and bluebunch inhibit curlycup gumweed and prairie aster growth on disturbed rangeland soil, and that interspecific competition may be a barrier to the successful establishment of early successional forbs.