Poster Session #65: Global Change.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC


UV-B affects decomposition and decomposers in a native ecosystem in Tierra del Fuego, Argentina.

PANCOTTO, VERONICA*,1, SALA, OSVALDO1, CABELLO, MARTA2, LOPEZ, NANCY3, BALLARE, CARLOS1, CALDWELL, MARTYN4, SCOPEL, ANA1, 1 Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura, Buenos Aires, Argentina2 Instituto Spegazzini, La Plata, . Argentina3 Facultad de Ciencias Exactas y Naturales- UBA, Buenos Aires, Argentina4 Utah State University, Logan

ABSTRACT- Tierra del Fuego, Argentina (55oS), receives increased solar ultraviolet-B radiation (UV-B, 280-315 nm) annually in the Austral Spring (September-December) as a result of Antarctic stratospheric ozone depletion. We conducted a field study in Tierra del Fuego National Park to examine direct and indirect effects of solar UV-B radiation on decomposition of Gunnera magellanica, a native perennial herb and on decomposer organisms (bacteria and fungi) associated with this species. Indirect effects of UV-B can occur via changes in the chemical composition of litter, whereas direct effects result from changes in decomposer organisms and/or differences in the photochemical breakdown of litter. We designed a full factorial experiment using senescent leaves that had received either near-ambient or attenuated UV-B during growth. The leaves were distributed in litterbags and allowed to decompose under near-ambient or reduced solar UV-B. We found that the level of UV-B radiation received by the plants during growth did not affect decomposition rate; however UV-B treatment during decomposition caused a 5% higher mass loss under reduced UV-B than under near-ambient UV-B. Colonization of fungal species was affected differentially by solar UV-B radiation, but bacterial colonization did not differ between treatments. These results demonstrate that, in this ecosystem, the sensitivity to UV-B shown by fungal community is more important than the photochemical breakdown of litter in the decomposition process.

KEY WORDS: ultraviolet-B radiation, ozone hole, decomposition process, Gunnera magellanica