@article {50773,
	title = {Influence of an exotic species, acroptilon repens (L.) DC. on the initial survival and growth of native grasses},
	journal = {Plant Ecology},
	volume = {166},
	number = {2},
	year = {2003},
	month = {September 1, 200},
	pages = {157-166},
	abstract = {<p>Our objective was to evaluate the effects of an invasive perennial forb, Acroptilon repens (Russian knapweed) on seed germination and seedling survival of four native grass species that are important in semiarid grasslands of North America. Greenhouse experiments and field studies conducted at three sites in Colorado were used to examine the response by four perennial grasses: Bouteloua gracilis, Koelaria cristata, Sporobolus cryptandrus, and Agropyon smithii to A. repens. In the greenhouse, seeds of each species were sown in pots that contained either live A. repens roots, litter on the soil surface, or both roots and litter. Field transects were placed inside stands of A. repens with adjacent control transects in the surrounding grass-dominated community. Germination and initial survival were decreased by the presence of A. repens roots for K. cristata (35\%), B. gracilis (31\%), and S. cryptandrus (44\%) in the greenhouse, and 57, 32, and d36\%, respectively, in the field. Root weight was decreased by the presence of A. repens roots for both B. gracilis and K. cristata by more than 55\% in the greenhouse. A. smithii survival and growth was unaffected by A. repens in either the greenhouse or the field. These species-specific responses to the presence of A. repens may explain, at least in part, differences in susceptibility and recovery of sites with different native grass species composition.</p>
},
	doi = {10.1023/A:1023221024593},
	url = {/files/bibliography/03-011.pdf},
	author = {Grant, D.W. and Debra C. Peters and Beck, K.G. and Fraleigh, H.D.}
}
@proceedings {51218,
	title = {Perennial grass survival response to Russian knapweed soil allelochemicals},
	volume = {51},
	year = {1998},
	month = {1998},
	pages = {65-66},
	abstract = {<p>Russian knapweed is an aggressive, noxious weed that dominates areas by forming monocultures. Development of Russian knapweed monocultures can be partly explained by allelopathy. Russian knapweed exudes polyacetylenes from its roots throughout the growing season and these compounds have been shown to inhibit the growth of certain plant species. A field experiment was established to determine the influence of Russian knapweed soil allelochemicals in situ on the seedling growth of lettuce, blue grama, western wheatgrass, prairie junegrass, and sand dropseed. The experiment was a randomized complete block design with 4 replications. Each transect included 10 seedlings of each bioassay species transplanted inside and directly outside a dense stand of Russian knapweed. Seedlings were irrigated over the course of 15 days. Seedling vigor was ranked visually at 3-day intervals. Blue grama survival inside the stand was 30\% less than outside 3 days after the experiment began. Survival of prairie junegrass, the stand, sand dropseed, western wheatgrass, were less inside compared to outside the stand. A greenhouse experiment was also completed to assess allelopathic potential of Russian knapweed infested soils at three soil depths, (0 to 5, 5 to 10, and 10 to 15 cm). The greenhouse experiment was a randomized complete block design with 4 replications. Response variables, including plant height, number of leaves/tillers, and a visual estimate of vigor, were measured at the onset of the experiment and after 1, 3, and 5 weeks. Differences were not detected between the treatments. However, volunteer seedling emergence was significantly lower for soil from inside the stand. The results will be used to develop an allelopathic parameter for a computer simulation model of Russian knapweed invasion dynamics.</p>
},
	author = {Grant, D.W. and Beck, K.G. and D.P. Coffin}
}
