|Chimner, Rod - COLORADO STATE UNIVERSITY|
|Welker, Jeff - UNIVERSITY OF ALASKA|
Submitted to: Ecological Society of America Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 15, 2005
Publication Date: August 10, 2005
Citation: Blumenthal, D.M., Chimner, R., Welker, J., Morgan, J.A., Lecain, D.R. 2005. Manipulation of precipitation and N alters weed invasion of northern mixed-grass prairie. Ecological Society of America Annual Meeting Proceedings. August, Montreal, Canada. CDROM Abstract. Technical Abstract: Because many invasive weeds are most successful in high-resource environments, global changes that increase plant resources may exacerbate weed invasion. In the Northern Mixed-Grass Prairie region, which contains the largest remaining expanse of native grassland in North America, changes have been predicted for both precipitation and N deposition. We examined the effects of precipitation and N on invasive perennial forbs: Centaurea diffusa, Euphorbia esula, Linaria dalmatica, and Gypsophila paniculata. Weed seeds were planted into mixed-grass prairie treated with a factorial combination of nitrogen addition (4 g m-2 yr-1 of NH4NO3), snow fences to increase snow accumulation, and rainout shelters or irrigation to halve or double summer rainfall, respectively. Increased snow accumulation was critical for establishment of all weed species, leading to a 13-fold increase in total weed height one year after seed addition. In adjacent plots without weeds, increased snow doubled above-ground biomass of established native species. Changes in summer precipitation had smaller, less consistent effects on weed establishment, with the only significant effect observed for Gypsophila. Nitrogen addition did not influence weed establishment. These results suggest that changes in the magnitude of or variation in winter precipitation could increase invasion in the Northern Mixed-Grass Prairie.