The mechanistic spread of knapweed in arid environments.
Leanna Reynolds, Melanie Ballard, and Paul Grossl. Plant, Soils & Biometeorology Dept., Utah State University, UMC 4820, Logan, UT, 435-797-1564, firstname.lastname@example.org Knapweed species are an aggressive and highly invasive noxious group of weeds that, once established, can create large monocultures reducing biodiversity of wildland flora. In part their successful spread is due to the elemental and organic allelopathic properties of the plants. Two of the knapweed species, Acroptilon repens (Russian knapweed) and Centaurea maculosa (Spotted knapweed) have been found to exude allelopathic chemicals from their root systems that are toxic to some native plants; A. repens releases 7,8-benzoflavone (α-naphthoflavone) and C. maculosa releases (-)-catechin. Determining the conditions resulting in optimum sorption of 7,8-benzoflavone and (-)-catechin to soils, making the phytotoxins less bioavailable to native species, could help provide an environmentally sound means of controlling the spread of Russian and Spotted knapweed. This study focuses on the interaction between two native bunchgrasses (Pseudoroegneria spicata and Sporobolus airodes) and Russian knapweed in a controlled arid environment. The project is a hydroponic study of six treatments with each grass grown separately beside the Russian knapweed and controls for each plant. This design gave optimum contact between roots as they became entangled during growth, investigating the effect of 7,8-benzoflavone on the native grasses. Preliminary visual results indicate Russian knapweed is highly detrimental to the growth of Pseudoroegneria spicata and only minimally detrimental to Sporobolus airodes.