Submitted to: Journal of Arid Environments
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/3/2011
Publication Date: 5/1/2011
Publication URL: hdl.handle.net/10113/49744
Citation: Mangla, S., Sheley, R.L., James, J.J., Radosevich, S.R. 2011. Role of competition in restoring resource poor arid systems dominated by invasive grasses. Journal of Arid Environments. 75:487-493. Interpretive Summary: Invasive annual grasses are one of the most serious threats to rangeland agricultural in the western US. Restoring annual grass infested rangeland is necessary to protect the ecosystem and agricultural production. Competition from annual grasses during the initial phase of restoration is considered a primary reason establishment fails. We tested the degree to which establishment was controlled by competition in the hot-dry portion of sagebrush-steppe biome. We could not find any effects of competition on bluebunch wheatgrass or Sandberg’s bluegrass from either cheatgrass or medusahead during the first two years of establishment. Managers may improve establishment of desired species by focusing efforts on overcoming abiotic barriers to establishment, rather than controlling annual grasses in harsh environments during the initial phase of restoration.
Technical Abstract: A failure to distinguish between competition intensity and importance limits our understanding of the role competition plays in structuring plant communities in resource poor environments. We quantified competition intensity and importance in an arid, resource poor system, using a two-year addition series field experiment where densities of two invasive (cheatgrass and medusahead) and two native (Sandberg’s bluegrass and bluebunch wheatgrass) species were manipulated. We hypothesized that 1) competition would be intense between invasive and native species but 2) competition would be unimportant in explaining variation in target plant biomass relative to all other factors driving variation in biomass. We did not observe high competition intensity between invasive and native plants and, as a consequence, competition was unimportant in influencing target plant biomass. Our results suggest that in abiotically driven environments, neither the intensity of competition nor competition importance significantly influenced plant community structure for the first two years plants were establishing. We suggest that land managers may be more successful at management and restoration of degraded ecosystems by overcoming the barriers associated with abiotic factors rather than focusing on treatments that control competition in resource poor systems.