Growth responses to ultraviolet-B radiation of two Carex species dominating an Argentinian fen ecosystem

Solar ultraviolet-B radiation (UV-B, 280–315 nm) in the Southern Hemisphere has been increasing over the last few decades due to seasonal stratospheric ozone depletion associated with the ‘ozone hole’ and a more general erosion of the stratospheric ozone layer. We studied the effect of UV-B radiation on growth responses of Carex curta and C. decidua, the two most dominant sedges in a fen ecosystem in Tierra del Fuego (Argentina) in field plots and growth chambers where UV-B radiation was manipulated using different transparent plastic films that either transmitted or attenuated UV-B radiation. In the field, leaf and spike elongation of both species was unaffected by UV-B treatments in all four seasons studied (1997/98 through 2000/2001). Specific leaf areas (SLA) were only measured in the last two seasons and remained unaffected by UV-B for both species in the third field season. However, SLA decreased for C. curta in the fourth season but increased for C. decidua under near-ambient UV-B. Ecosystem specific root length was unaffected by UV-B. Although UV-B did not have a statistically significant effect on biomass production, there was a trend for a 15% higher production under near-ambient UV-B in the fourth year (P = 0.064). In the growth chambers, simulated ambient UV-B approximately equivalent to ambient UV-B in Tierra del Fuego stimulated seedling emergence of C. curta but reduced emergence of C. decidua; leaf elongation remained unaffected in both species. While plant morphology of C. curta remained unaffected by UV-B radiation, C. decidua had fewer tillers per plant, however tillers had more leaves and biomass under simulated ambient UV-B than under reduced UV-B radiation. The SLA of C. curta was unaffected by UV-B treatments; however, it was significantly lower for C. decidua under simulated ambient UV-B. Root morphology remained unaffected by UV-B for C. curta but roots of C. decidua were significantly thicker under simulated ambient UV-B. Taken collectively, our findings demonstrate that even moderate changes in UV-B radiation (e.g., corresponding to those expected with current stratospheric ozone depletion) may influence growth, morphology and biomass allocation in a species-specific manner for these native sedges in growth chambers and might also affect competitive relationships of these species in the field. Die ultraviolett-B-Strahlung (UV-B, 280–315 nm) über der Südhemisphäre ist in den letzten Dekaden bedingt durch eine saisonale Abnahme an stratosphärischem Ozon (“Ozonloch”) und einer zusätzlichen, eher generellen Erosion der stratosphärischen Ozonschicht angestiegen. Wir untersuchten den Effekt von UV-B-Strahlung auf verschiedene Wachstumsparameter von Carex curta und C. decidua, den zwei dominierenden Seggenarten in Seggenried-Ökosystemen in Tierra del Fuego (Feuerland, Argentinien) in einem Feldversuch (Versuchsdauer: vier Saisonen von 1997/1998 http://www.elsevier-deutschland.de/baae