ARS | Publication request: WEED INVASION AND DIVERSITY RELATIONSHIPS IN PASTURE COMMUNITIES

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: October 20, 2002
Publication Date: November 12, 2002
Citation: Tracy, B.F., Sanderson, M.A. 2002. Weed invasion and diversity relationships in pasture communities [abstract]. American Society of Agronomy Meetings. Paper No. C06-tracy134713-oral. 2002 CDROM.

Technical Abstract: Ecological research has shown that high plant diversity can reduce weed invasion in some plant communities. In 1999, we began a study to determine whether greater forage diversity in cool season pastures could reduce weed abundance. The study consisted of three components. First, weed abundance was evaluated over 1999 and 2000 growing seasons in experimental pasture communities ranging from 1 to 15 species. We then evaluated weed germination and growth in a greenhouse experiment by sowing curly dock (Rumex crispus L.) seeds with forage mixtures of differing diversity. Lastly, we explored the relationship between weed abundance and forage diversity in 37 pastures that were surveyed across the northeast United States. In the field experiment, weed abundance was significantly lower in the most diverse communities. This effect, however, was mainly due to the greater forage biomass in these mixtures and not diversity per se. Higher forage diversity repressed curly dock germination by 36% and final biomass up to 90% in the greenhouse study. This repressive effect was primarily due to the presence of large, productive species in the forage mixtures. The pasture survey found a significant negative relationship between that weed abundance and forage diversity at the pasture scale (r2 = 0.21, p=0.004, df = 1,35). Results from our study suggest that high forage plant diversity may help reduce weed invasion in pastures. This effect likely results from large, productive forage species that have a greater probability of being present in more diverse forage mixtures.