PARENT SESSION
Poster Session #50: Climate Change.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Response of a Tierra del Fuego peatland to six field seasons of UV-B radiation manipulation.

Robson, Thomas^*,1, Ballar, Carlos², Sala, Osvaldo², Scopel, Ana², Caldwell, Martyn¹, ¹ Utah State University, Logan, Utah.² IFEVA-CONICET, Universidad de Buenos Aires, Capital Federal, Buenos Aires, Argentina.

ABSTRACT- In a long-term field study in Tierra del Fuego, southern-most Argentina, the plant community in a Sphagnum peat bog has been studied under different UV-B radiation treatments. Plastic filters are used to control the dose of UV-B radiation received in permanent plots from September to March. Sample plots beneath polyester film (equivalent to mylar), which attenuates UV-B radiation are compared with near-ambient plots, under a transparent polyfluorine film (aclar). The four species most closely studied were found to respond differently to reduced UV-B radiation. Tetroncium magellancium exhibited consistently faster leaf growth and longer leaf length under the reduced UV-B treatment in the forth, fifth and sixth years of the study. The accumulated effect of reduced UV-B resulted in consistently increased growth of the Sphagnum magellacium carpet throughout the study, and remained significant after five years. Dwarf Nothofagus antarctica bushes, which emerge from the Sphagnum , showed a tendency for increased growth and leaf production under reduced UV-B only in the fifth year of the study, and no affects on Empetrum rubrum growth or physiology were encountered. The potential consequences of these changes for community structure in the peatland are explored and related to the observed trends in community dynamics. Possible reasons for the differential response of these species to UV-B radiation, such as variable synthesis of UV screening compounds are suggested, and the changes seen contrasted with those observed in other studies with comparable species and treatments.

KEY WORDS: Ozone depletion, peatland, UV-B radiation, plant community dynamics