Impacts of solar ultraviolet-B radiation on terrestrial ecosystems of Tierra del Fuego (southern Argentina). An overview of recent progress.

BALLARE, C. L.; ROUSSEAUX, M. C.; SEARLES, P.S.; ZALLER, J. G.; GIORDANO, C. V.; ROBSON, T. M.; CALDWELL, M.M.; SALA, O. E.; SCOPEL, A.L.

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY

Año: 2001 vol. 62 p. 67 - 77

1011-1344

The southern part of Tierra del Fuego, in the southernmost tip of South America, is covered by dense Nothofagus spp. forests and Sphagnum magellanicum 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 by using two types of plastic film to manipulate UV-B radiation. We have addressed two basic problems: i) Do the fluctuations in UV-B 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 and graminoid species of this region (growth reduction #12 %), whereas no consistent inhibitory effects could be detected in 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 to ambient UV-B such as increased sunscreen levels and DNA repair capacity; (4) ambient UV-B has significant effects on heterotrophic organisms, included marked inhibitory effects on insect herbivory. The results from the experiments summarized in this review clearly indicate that UV-B influences several potentially important processes and ecological interactions in the terrestrial ecosystems of Tierra del Fuego.