Impacts of native grasses and cheatgrass on Great Basin forb development

Abstract

Land managers need more information on native forb growth and interactions between forbs and grasses to improve degraded sagebrush steppe habitats in the Great Basin, and to increase the diversity of revegetation seed mixes. This is especially important in areas infested with Bromus tectorum (cheatgrass), an annual grass present in more than 100 million acres of the Great Basin. To gather information on forb growth and measure the effects of both native grasses and B. tectorum on forbs, I conducted a greenhouse experiment with 5 native forbs: Lomatium sp., Eriogonum umbellatum, Machaeranthera canescens, Penstemon speciosus, Sphaeralcea munroana; two native grasses: Elymus elymoides and Poa sandbergii; and B. tectorum. Forbs were grown alone or with a grass, and were harvested after 6, 9 or 12 weeks of growth. Excluding Lomatium, which became dormant before week 12, forbs did not differ in shoot relative growth rate when growing alone, but the root relative growth rate of P. speciosus was 50% greater. Neither native grass reduced the biomass of any forb, but growth rate was reduced for two forbs.

Citation

Parkinson, Hillary Ann. 2008. Impacts of native grasses and cheatgrass on Great Basin forb development. Bozeman, MT: Montana State University. Thesis. 77 p.