Seed mix performance and cheatgrass suppression on arid rangelands

Authors: Clements, Darin - Charlie; Harmon, Daniel - Dan; BLANK, ROBERT - Retired ARS Employee

Submitted to: Rangelands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2022
Publication Date: 4/29/2022
Citation: Clements, D.D., Harmon, D.N., Blank, R.R. 2022. Seed mix performance and cheatgrass suppression on arid rangelands. Rangelands. 44(2):129-135. https://doi.org/10.1016/j.rala.2022.02.003.
DOI: https://doi.org/10.1016/j.rala.2022.02.003

Interpretive Summary: The restoration or rehabilitation of degraded rangelands throughout the Intermountain West is very challenging due to annual invasive species which exhibit high growth rates and seed production. To add to this challenge, invasive annual grasses, such as cheatgrass (Bromus tectorum L.), out compete native perennial species for limited resources, especially in arid environments. The accidental and subsequent invasion of cheatgrass throughout millions of hectares of Intermountain West rangelands has truncated secondary succession by providing a fine-textured early maturing fuel that has increased the chance, rate, spread and season of wildfire. The increase in wildfire size and frequency can significantly reduce recovery of native species and increase annual grass dominance. Aggressive and effective weed control methods are essential in reducing cheatgrass densities to improve seedling survivability of seeded species, as well as selecting seed mixes that will improve seeding success. This study was initiated to test native, introduced and native/introduced seed mix performance and the ability of these seed mixes to suppress cheatgrass densities. Native seed mix performed very well compared to introduced and native/introduced seed mixes when the site received favorable precipitation, > 220 mm/year, yet when the site received < 220 mm/year, the native mix did not perform well and was not effective at suppressing cheatgrass.

Technical Abstract: The accidental and subsequent invasion of cheatgrass throughout millions of hectares of Intermountain West rangelands has truncated secondary succession by providing a fine-textured early maturing fuel that has increased the chance, rate, spread and season of wildfire. The restoration or rehabilitation of degraded rangelands throughout the Intermountain West is very challenging due to annual invasive species which exhibit high growth rates and seed production. To add to this challenge, invasive annual grasses, such as cheatgrass (Bromus tectorum L.), out compete native perennial species for limited resources, especially in arid environments. We tested the use of a pre-emergent herbicide, Imazapic to initially control cheatgrass and then followed this treatment up with the testing of native, introduced and native/introduced seed mixes at two separate sites in northern Nevada. Native seed mix experienced as much as 7.9 established perennial grasses/m² and as low as 1.1/m². When the site received less than 220 mm of annual precipitation, the native seed mix significantly declined in performance and was not effective at suppressing cheatgrass compared to introduced and native/introduced seed mixes that averaged a high of 10.7 established perennial grasses/m² and a low density of 2.3/m².