Ballaré, C. L., M. C. Rousseaux, P. S. Searles, J. G. Zaller, C. V. Giordano, T. M. Robson, M. M. Caldwell, O. E. Sala, and A. L. Scopel. 2001. Impacts of solar ultraviolet-B radiation on terrestrial ecosystems of Tierra del Fuego (southern Argentina). Journal of Photochemistry and Photobiology 62:67-77. (Abstract)

------The southern part of Tierra del Fuego, in the southernmost tip of South America, is covered by dense forests and peat bogs, which are subjected to the influence of ozone depletion and to increased levels of solar ultraviolet-B radiation (UV-B). Beginning in 1996 our group has been studying the biological impacts of solar UV-B on natural ecosystems of this region. We have addressed two basic problems: i) Do the fluctuations in ozone levels under the influence of the Antarctic ozone "hole" have any measurable biological impact? ii) What are the long-term effects of solar UV-B in the Tierra del Fuego ecosystems? In this paper, we provide an overview of the progress made during the first four years of the project. We highlight and discuss the following results: (1) Ambient UV-B has subtle but significant inhibitory effects on the growth of herbaceous species of this region, whereas no consistent inhibitory effect could detected in the group of woody perennials; (2) in the species investigated in greatest detail, Gunnera magellanica, the inhibitory effect of solar UV-B is accompanied by increased levels of DNA damage in leaf tissue, and the DNA damage density in the early spring is clearly correlated with the dose of weighted UV-B measured at ground level; (3) the herbaceous species of the region show little or no acclimation responses (e.g., increased sunscreen levels, increased DNA repair capacity) to ambient UV-B; (4) ambient UV-B has significant effects on heterotrophic organisms of the ecosystems investigated; the inhibitory effect of solar UV-B on the levels of insect herbivory are particularly noticeable, and are consistent with the results reported for other ecosystems of the world.