Pre-adaptation of cheatgrass for the Great Basin

Authors: Clements, Darin - Charlie; YOUNG, JAMES - Retired ARS Employee; Harmon, Daniel - Dan

Submitted to: The Progressive Rancher
Publication Type: Popular Publication
Publication Acceptance Date: 10/26/2023
Publication Date: 11/10/2023
Citation: Clements, D.D., Young, J.A., Harmon, D.N. 2023. Pre-adaptation of cheatgrass for the Great Basin. The Progressive Rancher. 23(8):24-26.

Interpretive Summary:

Technical Abstract: Cheatgrass has been a successful invader of the Great Basin largely because of a series of pre-existing conditions. These include: 1) evolution to sagebrush ecosystems in North America without highly competitive annuals, 2) evolution of cheatgrass in a similar potential environment on a different continent where agriculture had existed for millennia, 3) introduction of cattle into semiarid to arid environments in North America by ranchers who had no experience with temperate desert environments, 4) mechanization and subsequent expansion of cereal grain production in western North America, and 5) deep-seated inertia resisting the end of open public rangelands in the American West. These preconditions had to be aligned just so in space and time for cheatgrass to be successful. Cheatgrass evolved in middle Asia, the same area where cattle, sheep, horses and goats are thought to have been domesticated. Working at a very early agricultural site in the mountains of Iran, archaeologist Kent Flannery and botanist Hans Helbaek identified carbonized seeds recovered from fossil hearths. Flannery and Helbaek were able to follow the evolution of small grain crops, especially wheat and barley, from seeds that hunter-gatherers collected from wild grasses through the evolutionary process that produced modern cereal species. In their investigation, they reported that seed species that are considered weeds, occurred together with seeds of cultivated crops. Cheatgrass has long had the ability to invade habitats without wildfire, it is this ability that allows this species to invade voids in habitats, build seed banks and then following wildfire, convert those habitats to cheatgrass dominance because of its’ active and persistent seed banks. The loss or significant decrease of perennial grasses is the catalyst for cheatgrass dominance as the perennial grasses have the inherent ability to suppress cheatgrass and associated fuels. Once the perennial grass is reduced and no longer provides this function, cheatgrass provides a fine-textured early maturing fuel that increases the chance, rate, spread and season of wildfire. Cheatgrass truncates secondary succession by out-competing perennial species for limited resources at the seedlings stage. In combination with severely overgrazed rangelands, increased cultivation for irrigated hay and the Continental railroad (prime transportation of contaminated grains), cheatgrass widely spread throughout the Great Basin in an environment it was already pre-adapted to.