Suppression of cheatgrass by established perennial grasses: I. mechanisms

Authors: Blank, Robert - Bob; Morgan, Tye

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/15/2009
Publication Date: 2/7/2010
Citation: Blank, R.R., Morgan, T.A. 2010. Suppression of cheatgrass by established perennial grasses: I. mechanisms. In: Outline abstracts, Joint Annual Meeting of the Society for Range Management and the Weed Science Society of America, Denver, CO.

Interpretive Summary:

Technical Abstract: Cheatgrass is often considered a competitive species. In a greenhouse experiment using rhizotrons, we tested the effect of established perennial grasses (Indian ricegrass, creeping wildrye, and Snake River wheatgrass) on the growth of cheatgrass. The soil was a sandy loam A horizon of a Xeric Haplocalcid from a winterfat community that has been invaded by cheatgrass for about 10 years. The experiment was conducted over 5 growth cycles of 80 days each with the following treatments imposed: 1st – cheatgrass planted between perennial grasses established for 60 days; 2nd – perennials clipped (15 cm left standing) and cheatgrass planted; 3rd – perennials clipped, activated carbon mixed in upper soil, and cheatgrass planted; 4th – perennials clipped, soil top-dressed with complete fertilizer, and cheatgrass planted; 5th – perennial grasses killed and cheatgrass planted. We also planted cheatgrass without competition to serve as a control. Water was not limiting in this study. Response variables measured at the end of each growth cycle included above-ground mass of cheatgrass and its tissue concentrations of C and N. Established perennial grasses significantly retarded the growth of cheatgrass relative to the controls; after the 1st growth cycle, above-ground cheatgrass biomass of controls averaged 3479 times greater than cheatgrass planted between the perennials. Overall, biomass of cheatgrass, grown between established perennials, increased considerably after fertilizer addition (4th growth cycle) and dramatically upon death of the perennials (5th growth cycle). For all growth cycles, suppression of cheatgrass growth was greatest between Snake River wheatgrass and least between Indian ricegrass. Tissue N and C data and its change with growth cycle (treatments) suggest that established perennials reduced N availability to cheatgrass. The data, however, also support other mechanisms by which established perennial grasses suppress cheatgrass, including allelopathy.