Elevated UV-B radiation has no effect on litter quality and decomposition of two dune grassland species: evidence from a long-term field experiment

From studies on living plant tissues it has been inferred that elevated UV‐B radiation could negatively affect litter quality and subsequent decomposition. However, in general, the effects of UV‐B radiation on litter chemistry and decomposition reported in the literature are variable and are often only marginally (if at all) significant. This might be due to the ecologically unrealistic conditions under which these experiments were performed. We investigated the effects of elevated UV‐B radiation on litter quality and subsequent decomposition on initial litter chemistry and long‐term (2 years) decomposition of freshly senesced Carex arenaria and Calamagrostis epigejos leaf litter under ecologically realistic conditions. This material was collected from a dune grassland that had received UV‐B radiation treatments for three growing seasons. It was then used in a 2‐year decomposition study using litter bags. We found no significant effects of elevated UV‐B radiation on any of the litter chemistry parameters in either of the two species, nor did we find significant effects on litter decomposition. However, we did find significant differences in litter decomposition between the species. These differences were related to the interspecific differences in litter chemistry, particularly the litter phenolics concentration. These results show that litter quality and decomposition in dune grasslands are, also under ecologically realistic conditions, not affected by UV‐B radiation. Instead, litter decomposition is determined by constitutive interspecific differences in litter chemistry. In conclusion, with our results added to the already existing literature, the preponderance of evidence now clearly suggests that elevated UV‐B radiation has very little, if any, impact on litter quality and subsequent decomposition in real ecosystems.