Perennial grass suppression of cheatgrass: Comparisons among two natives and one exotic

Authors: BLANK, ROBERT - Retired ARS Employee; Clements, Darin - Charlie; MORGAN, TYE - Bureau Of Land Management; Harmon, Daniel - Dan; Allen, Fay

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/4/2019
Publication Date: 2/16/2020
Citation: Blank, R., Clements, D.D., Morgan, T., Harmon, D.N., Allen, F.L. 2020. Perennial grass suppression of cheatgrass: Comparisons among two natives and one exotic. Society for Range Management Meeting Abstracts. 73:88. February 16-20, 2020 Denver, CO.

Interpretive Summary:

Technical Abstract: Long-term control of the invasive annual grass, cheatgrass, is predicated on its biological suppression. Perennial grasses, which have been shown to effec-tively suppress cheatgrass, vary in their suppressive ability. We compared the ability of a non-native grass (‘Hycrest’ crested wheatgrass) and two native grasses (Snake River wheatgrass and bluebunch wheatgrass) to suppress cheat-grass. In a greenhouse setting with separate tubs, 5 replicates of each peren-nial grass was established for 96 days upon which two seeds of cheatgrass were then sown at distances of 10, 30, and 80 cm from the established plants. Water was not limiting to growth of cheatgrass. Relative to cheatgrass grown at 80 cm, all perennial grasses significantly reduced aboveground biomass at 30 cm (68% average reduction) and at 10 cm (98% average reduction). Sown at 10 cm from established perennial grasses, cheatgrass aboveground biomass was in-versely related with perennial grass root mass per unit volume of soil. All cheatgrass sown at 10 cm from ‘Hycrest’ crested wheatgrass died within 38 days. Before sowing of cheatgrass, soil 10 cm from established perennial grasses had significantly less mineral N than soil taken at 30 and 80 cm. Rel-ative to cheatgrass tissue N for plants grown at 80 cm, cheatgrass nearest to the established perennial grasses contained significantly less tissue N. All perennial grasses inhibited the NO2- to NO3- nitrification step; for ‘Hycrest’ crested wheatgrass, soil taken at 10 cm from the plant had a molar proportion of NO2- in the NO2- + NO3- pool of greater than 90%. In summary, a combination of reduced nitrogen availability, occupation of soil space by perennial roots, and attenuation of the nitrogen cycle contribute to suppression of cheatgrass.