HR: 17:00h
AN: B54A-05    [Abstracts]
TI: Effects of elevated nitrogen dioxide and carbon dioxide on the growth of Sugar Maple and Hemlock seedlings
AU: * Eller, A S
EM: ase3@cornell.edu
AF: Cornell University, Ecology and Evolutionary Biology, Ithaca, NY 14853 United States
AU: McGuire, K L
EM: mcguirek@umich.edu
AF: University of Michigan, Ecology and Evolutionary Biology, Ann Arbor, MI 48109 United States
AU: Sparks, J P
EM: jps66@cornell.edu
AF: Cornell University, Ecology and Evolutionary Biology, Ithaca, NY 14853 United States
AB: The partial pressure of nitrogen dioxide (NO₂) in the earth's atmosphere has been rising since the industrial revolution and is likely to continue rising due to the burning of fossil fuels. When NO₂ enters plant leaves, it can undergo reactions that produce nitrate, which can be a source of nutrient nitrogen for the plant. However, NO₂ is also an oxidant with the potential to damage cell membranes and decrease growth. The goals of this study were to examine the effect of NO₂ on plant productivity alone and in combination with elevated CO₂ under both nitrogen- and non-nitrogen-limiting conditions. To assess these effects, we conducted CO₂, NO₂, and CO₂ + NO₂ fumigations of sugar maple and eastern hemlock seedlings in open-topped chambers and measured relative growth rate, specific leaf area, root:shoot, and C:N of the leaves, stems, and roots. Sugar maple growth was reduced by 7% under elevated NO₂ when nitrogen was limiting. When nitrogen was not limiting and CO₂ was ambient, elevated NO₂ caused a 4% decrease in growth and when CO₂ was elevated there was no growth effect. Hemlock growth was increased by elevated NO₂ regardless of nitrogen status and under both partial pressures of CO₂; 3 and 8% increase in growth under ambient and elevated CO₂, respectively. These data suggest gaseous reactive nitrogen may augment or decrease the future growth effects of elevated CO₂ depending on plant species identity. In addition, perhaps because of differences in nitrogen metabolism and physiology, deciduous and evergreen tree species appear to have different responses to reactive nitrogen fumigation. These results underscore the need for examining the responses of vegetation to mixtures of gases representative of the future atmosphere rather than examining the influence of carbon dioxide alone.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0469 Nitrogen cycling
DE: 0476 Plant ecology (1851)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: Fall Meeting 2005