ARS | Publication request: Cheatgrass Biomass and Competition: Is a greenhouse fight a fair fight?

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 24, 2010
Publication Date: February 12, 2011
Citation: Clements, C.D., Harmon, D.N. 2011. Cheatgrass biomass and competition: Is a greenhouse fight a fair fight [abstract]? Society for Range Management. 64:65.

Technical Abstract: Revegetation of degraded rangelands is a tremendous challenge for land managers. Crested wheatgrass (Agropyron cristatum), a plant with the potential to compete with cheatgrass (Bromus tectorum), has been a valuable tool for land managers in decreasing fire frequency and promoting assisted succession towards native grass/shrub communities. Salt desert shrub habitats, often below the establishment potential of crested wheatgrass, are becoming increasingly threatened by cheatgrass invasion and fire. In response, we examined the potential for native annual forbs to suppress cheatgrass. Understanding an annual’s limitations, we initially observed the interaction between the annual’s presence and cheatgrass biomass, a fuel for fires. In a greenhouse study paired with field plots, we tested the effect of the presence of an annual on the biomass of cheatgrass. Our results found that the greenhouse study had more annual species significantly (P=0.05) affecting cheatgrass biomass (10/11 species) than the field test (2/11 species) [e.g. Greenhouse: control = 5.12g Amsinkia tesselata present = 1.39g (80% reduction), Field test: control = 4.83g, Amsinikia tesselata = 0.62g, (87% reduction)]. Under greenhouse conditions moisture may not be the limiting factor and nutrients become limiting. This results in cheatgrass having less competitive advantage. However, in the field our results found that annual species rarely established with cheatgrass competition. It is unlikely that assisted succession can occur without the prolonged suppression of cheatgrass and the presence of the assisting plant. The confounding results of greenhouse and field tests emphasize the requirement for on the ground “proofing” of cheatgrass greenhouse competition research.