Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 24, 2013
Publication Date: May 1, 2013
Repository URL: http://handle.nal.usda.gov/10113/56689
Citation: Russell, M., Vermeire, L.T., Dufek, N.A., Strong, D.J. 2013. Fire, defoliation, and competing species alter Aristida purpurea biomass, tiller, and axillary bud production. Rangeland Ecology and Management 66:290-296. Interpretive Summary: Aristida purpurea (purple threeawn) is a native perennial grass with poor forage quality that can dominate sites following severe disturbance. We examined effects of fire, clipping, and neighboring species on purple threeawn to develop techniques for reducing threeawn dominance. Final biomass, aboveground production, tillers and axillary buds were evaluated for burned and non-burned plants in 4 clipping treatments applied to each of the 3 species-pair combinations. Fire killed 36% of the threeawn plants. Biomass was less for non-burned plants when their neighbor was clipped than when neither plant was clipped, suggesting increased competition. Tiller counts of burned threeawn plants did not differ among clipping treatments, all of which had fewer tillers than non-burned plants that were not clipped or moderately clipped. Fire decreased the number of active and dormant threeawn axillary buds per plant by 25%. Threeawn comprised a greater percentage of pot biomass when grown with blue grama (46%) than with western wheatgrass (38%). Fire reduced threeawn from 60 to 23% of the pot biomass. Fire and grazing may inhibit perennial threeawn monocultures and restore diversity to threeawn-dominated plant communities.
Technical Abstract: Aristida purpurea (threeawn) is a competitive native perennial grass with monoculturistic tendencies and poor palatability. We examined effects of fire, defoliation, and interspecific/intraspecific planting for 1) threeawn responses in the presence of threeawn, Bouteloua gracilis, or Pascopyrum smithii, and 2) B. gracillis and P. smithii response with threeawn. Biomass, aboveground production, tillers and axillary buds were analyzed following 2 fire and 4 clipping treatments applied to 3 species-pair combinations in a completely randomized factorial design with 9 replications. Fire killed 36% of threeawn. Fire reduced surviving threeawn biomass 61% and reduced production 27%. Threeawn production was greatest when neither plant was clipped and least when competing species were moderately clipped, or when both plants were severely clipped. Tiller counts of burned threeawn were similar among clipping treatments, and less than non-clipped or moderately clipped plants not burned. Fire decreased threeawn axillary buds 25%. Moderately clipped plants had greater production than those from other clipping treatments across species. Threeawn percentage of pot biomass and was greater with B. gracilis (46 ± 3%) than P. smithii (38 ± 3%). Fire reduced threeawn from 60 to 23 ± 3% of pot biomass. Fire and grazing may inhibit threeawn monocultures and restore diversity.