Tuesday, August 3, 2010
Exhibit Hall A, David L Lawrence Convention Center
Background/Question/Methods The combustion of fossil fuels, animal husbandry practices, and the production and use of agricultural fertilizers have contributed to the large amount of atmospheric nitrogen deposition that occurs in the Midwest United States. Increases in nitrogen availability have been shown to reduce species diversity and alter species composition within nitrogen limited ecosystems. The West Beach area of the Indiana Dunes National Lakeshore is surrounded by industrialization, urbanization, and agriculture. The area annually receives approximately 16kg ha-1 ammonium and nitrate deposition collectively. The purpose of this experiment was to determine whether nitrogen availability disproportionately alters germination success among native species. The seeds of ten native plant species were germinated using five different concentrations of ammonium nitrate (NH4NO3) ranging from a control of 0.0g L-1 to a maximum of 2.7g L-1. After four weeks the percent germination of each species within each treatment group was determined. For each species, analysis of variance was used to compare the percent germination between treatment groups. If the germination success of a few species increases proportionate to available nitrogen while the germination of other species declines, then it is likely these species will be able to exploit more space within the community as nitrogen availability increases.
Results/Conclusions The germination patterns of the ten species were categorized into three groups. Four of the species Schizachyrium scoparium, Echinacea purpurea, Monarda punctata, and Lupinus perennis had increased germination success at low concentrations of NH4NO3 and decreased germination at high levels. The species Panicum virgatum, Penstemon grandiflorus, Elymus canadensis, and Sorghastrum nutans similarly had increased germination success at low levels of NH4NO3 but germination success at high levels were not significantly different from the control group. The germination success of the remaining two species Rudbeckia hirta, and Dalea purpurea did not significantly change from the control group at low levels of NH4NO3, but retained a significantly lower germination percent at high levels. The difference in germination patterns leads to a difference in rank order between treatment groups when ranking the percent germination of each species within each group. The data shows that as available nitrogen increases the germination success of many species will decrease as the germination success of few species remains high. This provides insight into a possible mechanism by which increases in available nitrogen could reduce species diversity within a plant community.
Results/Conclusions The germination patterns of the ten species were categorized into three groups. Four of the species Schizachyrium scoparium, Echinacea purpurea, Monarda punctata, and Lupinus perennis had increased germination success at low concentrations of NH4NO3 and decreased germination at high levels. The species Panicum virgatum, Penstemon grandiflorus, Elymus canadensis, and Sorghastrum nutans similarly had increased germination success at low levels of NH4NO3 but germination success at high levels were not significantly different from the control group. The germination success of the remaining two species Rudbeckia hirta, and Dalea purpurea did not significantly change from the control group at low levels of NH4NO3, but retained a significantly lower germination percent at high levels. The difference in germination patterns leads to a difference in rank order between treatment groups when ranking the percent germination of each species within each group. The data shows that as available nitrogen increases the germination success of many species will decrease as the germination success of few species remains high. This provides insight into a possible mechanism by which increases in available nitrogen could reduce species diversity within a plant community.
