ARS | Publication request: Suppressing downy brome following wildfires

Submitted to: Western Society of Weed Science
Publication Type: Abstract Only
Publication Acceptance Date: October 27, 2011
Publication Date: March 15, 2012
Citation: Clements, C.D., Harmon, D.N. 2012. Suppressing downy brome following wildfires [abstract]. Western Society of Weed Science. 64:15.

Technical Abstract: Downy brome (Bromus tectorum), more widely known as cheatgrass, has invaded millions of hectares of rangelands throughout the Intermountain West. Downy brome provides an early maturing, fine-textured fuel that has increased the chance, rate, season and spread of wildfires. In July 2006, a wildfire burned a xeric Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) community in northern Nevada. We implemented an experiment to test the importance of 1) timing of restoration/rehabilitation efforts, 2) mechanical weed control, and 3) plant species potential to be artificially seeded as well its’ ability to suppress downy brome. Sixty 20m x 60m plots were established, in which 30 plots were seeded in the fall of 2006 and the remaining 30 plots seeded in the fall of 2007. Half of each plot was disced to test this mechanical weed control practice of downy brome. The 2006 plots were disced in August of 2006, while the 2007 plots were disced in May 2007 and summer fallowed. The seeded treatments were A) ‘Hycrest’ crested wheatgrass (Agropyron cristatum), B) Sherman big bluegrass (Poa ampla), C) Bottlebrush squirreltail (Elymus elymoides) and D) a mixture of these species with Indian ricegrass (Achnatherum hymenoides), Wyoming big sagebrush, ‘Immigrant’ forage kochia (Bassia prostrata) and ‘Ladak’ alfalfa (Medicago sativa). Discing did decrease the germination density in the seed bank 300.5/m² down to 88.6/m² in the 2006 plots and 382.1/m² down to 182.2/m² in the 2007 plots. There were no significant differences when comparing seeded species survival in the disced –vs- undisced plots though. The 2006 seeded treatments A) crested wheatgrass and D) mix were most successful at establishing, 9.3/m² and 9.7/m² compared to B0 Sherman big bluegrass, .75/m², and C) squirreltail, 1.1/m², respectfully. Establish (two year old plants) seeded treatments A) crested wheatgrass and D) mix, significantly reduced downy brome densities, 6.2/m² and 7.5/m² compared to 126.1/m² for big bluegrass and 175.6/m² for squirreltail. Added downy brome suppression was also recorded for those plots seeded the first fall following the wildfire (2006) as increased success of seeded species was experienced.