PARENT SESSION
Wednesday, August 9, 8:00-11:30 am
COS 49 - Biogeochemical processes and dynamics
L-13, Lobby Level, Cook Convention Center
Presiders: J Edwards and C Cleveland
C:N:P stoichiometry of Antarctic tundra microcosms under increased temperature, precipitation, and soil glucose addition.
Bryant, David*,1, Strauss, Sarah1, Thomey, Michell1, Ruhland, Christopher2, Day, Thomas1, 1 Arizona State University, Tempe, AZ, USA2 Minnesota State University, Mankato, MN, USA
ABSTRACT- Mean annual temperature of the West Antarctic Peninsula has increased by 5o C over the last 50 years. Precipitation may also be increasing, but trends are not clear. Plant production is limited by temperature, therefore nutrients (primarily from marine bird and mammal excreta) are generally in excess of plant demand. We tested the effects of increased infrared radiation, precipitation and reduced net nutrient mineralization (by glucose addition) on 80 cm dia. tundra microcosms at Palmer LTER (64.8o S lat. 64.1o W long.). Total mean microcosm (weighted by live aboveground biomass) C:N, C:P and N:P ratios were low ( mean [s.e] = 22.94[0.38], 153.45[5.6], 6.75[0.28]; N=78, respectively ) and highly variable within and across treatments, showing no significant effects via 3 way ANOVA. Instantaneous gross primary production rates, measured weekly, were significantly lower in microcosms receiving glucose additions compared to controls (repeated measures MANOVA F = 15.09; p = 0.0002). Species level ANOVA, for the dominant vascular plant species; Antarctic pearlwort (Colobanthus quitensis), showed significant effects of heat and water treatments (F= 3.57; p = 0.0026) on aboveground N:P ratio (overall means = heat; 5.67[0.24] water; 5.82[0.24]). Pearlwort in glucose treated microcosms had significantly higher N:P ratios (8.32[0.55]) than controls (6.57[0.38]) with significant heat X water X glucose interactions. No significant effects of any treatment were shown for N:P ratios of other microcosm taxa; moss or Antarctic hairgrass (Deschampsia antarctica).
Key words: Antarctica, Nutrient stoichiometry, Global Change