Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/6/2005
Publication Date: 11/6/2005
Citation: Monaco, T.A., Johnson, D.A., Norton, J.M., Leonard, E.D. 2005. Altering plant-successional trajectories following wildfire in sagebrush-steppe communities. ASA-CSSA-SSSA Annual Meeting Abstracts. Interpretive Summary:
Technical Abstract: Invasive annual species are known to proliferate following wildfires in semiarid shrub-steppe plant communities by capitalizing on large increases in plant available mineral nutrients associated with wildfires. Following a wildfire in August 2002, we established experimental plots in a Wyoming big sagebrush plant community in southern Idaho to determine the possible secondary succession trajectories when treatments were applied to either favor or eliminate invasion by alien annual species. We hypothesized that eliminating invasive annuals with a selective herbicide or hindering their growth by sequestering mineral N (NH4+ and NO3-) with sucrose additions would facilitate native species regeneration. Conversely, we hypothesized that the addition of mineral N would facilitate invasive weed dominance and decrease native species regeneration. Fifteen plots were randomly assigned to an untreated control or 1 of the following 4 treatments: 1) imazapic herbicide (applied in first year at 100 g ha-1), 2) sucrose (1,000 kg ha-1yr-1), 3) low N (60 kg NH4NO3ha-1yr-1), and 4) high N (120 kg NH4NO3ha-1yr-1). Eight months after treatment, density of the dominant perennial grass (Poa secunda) was unaffected by treatments, but density of the alien annuals, Bromus tectorum and Sisymbrium altissimum, decreased in the herbicide and sugar treatments relative to the control. One year after treatment, the sucrose treatment had significantly lower NH4+ and NO3- than the N treatments. These data support our initial hypotheses and suggest that treatment effects on density of annual weeds and mineral N dynamics may have strong impacts on perennial grass regeneration.