Submitted to: Basic and Applied Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/11/2004
Publication Date: 12/13/2004
Citation: Tracy, B.F., Renne, I.J., Gerrish, J., Sanderson, M.A. 2004. Effects of plant diversity on invasion of weed species in experimental pasture communities. Basic and Applied Ecology.5(6):543-550. Interpretive Summary: Invasive weeds in pastures can reduce the yield and quality of forage and reduce grazing animal performance. Maintaining a diverse mixture of forage plants in pastures may be one way to reduce or prevent weed presence in pastures without the need for chemicals. In this research, we tested this idea with 16 different mixtures of forages containing up to eight forage species. Our results showed that forage mixtures based on tall fescue had less weed seed in the soil and fewer weeds growing in the plots than mixtures based on smooth bromegrass. Diverse mixtures contained fewer weeds; however, it seemed that the spatial distribution of forage species affected weed abundance more than simply the number of forage species. Our results show that planting or maintaining a diverse and evenly distributed mix of forage plants will reduce weed abundance in pastures.
Technical Abstract: Studies have shown that weed invasion into grasslands may be suppressed in diverse plant communities. Our main objective was to determine whether increased forage plant diversity in pasture communities could help reduce weed abundance in the aboveground vegetation and soil seed bank. We also tested whether soil seed banks of forage species could contribute to the originally sown species of pasture mixtures four and eight years after pasture establishment. Data was collected from a field experiment at the University of Missouri, Forage Systems Research Center in Linneus, MO. Using a point step method, aboveground plant species composition was measured in plots containing 1, 2, 3, 6 or 8 forage species that were grazed by cattle from 1998 to 2002. Composition of viable weed seed in plots was evaluated by identifying seedlings as they germinated over an 8 week period. We found that forage species did not form persistent seed banks that could be used to recruit desirable forage species into the aboveground vegetation. Aboveground weed abundance was unrelated to forage species richness (S). Weed abundance, however, declined as the evenness of forage species (J) increased in mixtures. The species composition of mixtures also affected weed abundance. Mixtures with a tall fescue (Festuca arundinacea Schreb.) base had less weed seed and aboveground weed abundance than those with a smooth brome (Bromus inermis Leysser) base. We concluded that maintaining diverse, evenly distributed mixture of forage plants should help suppress weed establishment in pasture communities.