Although most of these weeds are less of a fire hazard than cheatgrass is, scientists do not see them as a better option. For one, knapweeds are more poisonous than cheatgrass is. "The cheatgrass at least provides some forage, if you¿re raising livestock" says Tony Svejcar, a researcher for the U.S. Department of Agriculture. "Once the knapweeds come in, they basically have zero forage value."
Unlike cheatgrass, which can live alongside native plants such as sagebrush, knapweeds will eliminate most other plants in the area. Indeed, some researchers believe that Russian knapweed is allelopathic, which means the weed releases a chemical that suppresses other vegetation. Other scientists are dubious of this idea, preferring the hypothesis that the weeds are simply better competitors for natural resources. Nevertheless, invasive weeds are a persistent threat to rangeland ecology. Steve Dewey, an extension weed specialist at Utah State University, believes the new invasive weeds present an even greater threat than cheatgrass. He notes, "When something will crowd out cheatgrass, that¿s really bad stuff." -- D.W.
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