Effects of UV-B on decomposition in a shrub ecosystem in austral Tierra del Fuego, Argentina.

PANCOTTO, V., ; O. E. SALA, ; C. L. BALLARÉ, ; A. L. SCOPEL Y ; M. M. CALDWELL

Mar del Plata

Workshop; SPARC 2000 - Associated Workshop Impacts of UV Radiation on Terrestrial and Acquatic Ecosystems; 2000

The Antarctic "ozone hole" and a general erosion of the stratospheric ozone layer results in a major increase in UV-B radiation at the ground level over the southern part of South America. Tierra del Fuego (55oS) offers a great opportunity to assess UV-B effects because it represents the most austral terrestrial ecosystems with higher plants. We conducted a field study in the Tierra del Fuego National Park to examine the direct and indirect effects of  solar UV-B radiation on decomposition of Gunnera magellanica, a native perennial herb. We designed a full-factorial experiment with litter produced by plants growing under ambient and reduced UV-B that decomposed under ambient and reduced UVB.  We collected dead leaves from plants that had received either near-ambient or attenuated UV-B during growth in 1998-1999 and we used them in the decomposition experiment during the following season. We located the litter bags with G. magellanica below field plots in a shrub-ecosystem receiving either near-ambient or reduced solar UV-B and let litter decompose for a full growing season (1999-2000). We found that the level of UV-B received by the plants during growth did not affect decomposition; however, UV-B during decomposition affected litter mass loss that was 3% higher under reduced UV-B than under near-ambient UV-B (p<0.05). This effect could result from differences in the photochemical breakdown of litter and/or changes on decomposer organisms induced by solar UV-B.