Can defoliation reduce the abundance of smooth brome? An examination of phenology and defoliation timing.

Authors: Hendrickson, John; Carrlson, Andrew; FIELD, AARON - North Dakota State University; Clemensen, Andrea; YEOMAN, VANESSA - Us Forest Service (FS)

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/6/2022
Publication Date: 2/6/2022
Citation: Hendrickson, J.R., Carrlson, A.J., Field, A., Clemensen, A.K., Yeoman, V. 2022. Can defoliation reduce the abundance of smooth brome? An examination of phenology and defoliation timing.. Meeting Abstract. 1.

Interpretive Summary:

Technical Abstract: Smooth bromegrass (Bromus inermus Leyss.) is an introduced, cool-season, perennial grass that has invaded grasslands in the central and northern Great Plains. Anecdotal evidence suggests grazing may reduce smooth bromegrass abundance. However, little is known about the timing of grazing and how it impacts smooth bromegrass persistence. We compared the crowns of smooth bromegrass tillers that were defoliated either once (V1) or twice (V2) in the vegetative stage, in the elongation stage (E), in the reproductive (R) or left undefoliated (C) in three ungrazed exclosures over three years near Mandan, ND. Tillers in each treatment were marked with a different colored wire and excavated in the fall. Tillers were brought back to the laboratory, cleaned and each node position on the crown was categorized as an axillary bud, tiller, rhizome or leaf scar. The tillers were then placed in 0.1% w/v 2,3,5-triphenyl-2H-tetratozolium chloride (TTC) for 24 hours and activity levels on each position recorded. Tillers with inactive node positions were placed in Evan’s blue solution to determine viability. Positions that were not active or dead were considered dormant. Year and defoliation impacted the number of node positions, outgrowth and active meristems tiller-1. The R defoliation treatment had more total positions and active meristems than the controls (C). Outgrowth (tillers plus rhizomes) was less in the V2 treatment than the R (1.18 vs 1.83 outgrowth positions tiller-1 respectively). This data suggests that defoliation timing can impact the abundance of smooth bromegrass. This information will help managers design targeted grazing programs to reduce this invasive grass.