Spread of Forage Kochia in Invasive Annual Grass-Dominated Sagebrush Steppe

Abstract

Forage kochia (Kochia prostrata (L.) Schrad.) is a nonnative, semi-shrub that has been seeded in the western US to improve forage and habitat value of nonnative grasslands, compete with invasive plants, and as green-strips to reduce wildfire spread. As with other introduced plants, there are concerns that it may spread from areas it has been seeded. Current information on the potential for forage kochia to spread are inconclusive and reported results contradict each other. Thus, empirical studies investigating its spread over long-term (10 yr) periods of time are needed to guide land management decision. We investigated the spread of “Snowstorm” forage kochia at 11 invasive annual grass-dominated plant communities in southeastern Oregon a decade after they had been seeded. The seeding boundary was permanently marked at the time of seeding to ensure accurate measurements of forage kochia spread. Forage kochia established beyond the seeding boundary at two of the 11 seeded sites. The maximum distance that forage kochia spread from the seeding boundary was 65 cm. These results suggest that forage kochia does not readily spread in annual grass-dominated sagebrush steppe and what little spread it exhibited was over a relatively short distance. The risk of forage kochia spreading and dominating annual grass-invaded rangelands, at least in this region, appears minimal. Additional investigations of forage kochia spread in different environments and across various plant communities is warranted to inform land managers of any potential risks. Multiple decades evaluations of its potential to spread would also be important. Even though additional research would be valuable, our results that forage kochia does not readily spread suggest it may be a relatively safe option to seed to diversify nonnative grasslands.