Submitted to: Journal of Range Management
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/21/2005
Publication Date: 9/1/2005
Citation: Sheley, R.L., Carpinelli, M.F. 2005. Creating weed-resistant plant communities using niche-differented nonnative species. Journal of Range Management. 58(5):480-488. Interpretive Summary: Managing invasive weeds requires establishing and maintaining healthy plant communities that can resist invasion and/or re-invasion. We tested the idea that niche occupation and resource use by desired species could be designed to minimize weed invasion. Species were seeded in alone and in mixtures in areas with varying levels of spotted knapweed seeds in the soil. Species were carefully chosen based on their likelihood to occupy different niches. After seven years, desired species dominated mixtures and spotted knapweed was very low in those areas. Increasing niche occupation by desired species may enhance their resource use and productivity, thus minimizing unwanted invasive plants during rehabilitation of arid, marginally productive rangeland sites.
Technical Abstract: From 1996 through 2002, we tested the hypotheses that establishment and growth of non-native desirable species increases as desirable species richness of the seeding mixture increases, and spotted knapweed (Centaurea maculosa Lam.) Invasion decreases as desirable species richness increases. The experiment consisted of seven seeding monocultures and combinations totaling 4,500 seeds m2. Treatments were monocultures of each desired species (3 plots), all combinations of 2 desirable species (2,250 seeds m-2 per species; 3 plots), and 1 plot containing all 3 desirable species (1,500 seeds m-2 per species). The experiment was replicated four times at two sites by seeding each treatment with one of four background densities of spotted knapweed (1,250, 2,500, 3,750, and 7,500 seeds m-2; 7 treatments x 4 background densities = 28 plots) as blocks. Desirable species were completely niche-differentiated from each other at both sites in 1997 and 2002. Only one desirable species seeding in monocultures at each site yield greater biomass than in a mixture containing that species by 2002, suggesting that a rich variety of mixtures increases that at least one species in the mixture has traits matching the environmental conditions of site. In 2002, monocultures yielded about 3 times more spotted knapweed density and biomass than 3-species combinations at the dryer, less productive site, while alfalfa (Medicago sativa L., var. Arrow) monocultures limited knapweed as well as mixtures on the wetter, more productive site. In either case, stands of desired non-native species were well established in the presence of spotted knapweed, using a diverse mixture of non-native species that differed in niche, without the economic and ecologic limitations associated with using herbicides.