PARENT SESSION
Contributed Oral Session 34: Polar and Alpine Ecology: Climate Effects; Communities
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 524 A, Level 5, Palais des congrès de Montréal

Global warming in the Sub-Antarctic: Temperature response and temperature acclimation of plants from Heard Island.

Schortemeyer, Marcus^*,1, Bruhn, Dan¹, Ball, Marilyn¹, ¹ Ecosystem Dynamics Group, Canberra, ACT, Australia

ABSTRACT- Sub-Antarctic islands such as Heard Island are characterised by a cool, wet, windy, cloudy and very equable climate with few temperature extremes. Most vascular plant groups are at their southern distributional limit on Sub-Antarctic islands, and many of these islands are among the most rapidly warming environments on earth. On Heard Island, rapid deglaciation since the 1950s gives evidence to this. During the summer 2003/04, Heard Island was visited and the temperature response of photosynthesis of two species, the cruciferan megaherb Pringlea antiscorbutica and the tussock grass Poa cookii, was measured. This was done on plants experiencing different growth temperatures along an altitudinal gradient from sea level to >200 m asl. Measurements were taken for a temperature range from 4°C to 20°C, and above that where possible. P. antiscorbutica showed no apparent maximum of photosynthesis within the measured range, but plants grown at higher temperatures had acclimated, i.e. they had lower photosynthetic rates for a given leaf temperature. Leaf respiration of P. antiscorbutica also acclimated. P. cookii had maximum rates of net photosynthesis around 15°C and showed no acclimation. Acclimation, where it occurs, shifts optimum temperatures for carbon gain. Different abilities of species to acclimate to change will determine their ability to adjust to the effects of global warming.

Key words: global change, temperature, photosynthesis, respiration