The direct effects of UV-B radiation on Betula pubescens litter decomposing at four European field sites

A co-ordinated series of field experiments were conducted to consider the effects of elevated UV-B radiation applied directly to decomposing plant litter. Betula pubescens was decomposed under ambient and elevated UV-B (simulating a 15% ozone depletion) using outdoor irradiation facilities at Adventdalen, Norway (78 degrees N), Abisko, Sweden (68 degrees N), Amsterdam, The Netherlands (52 degrees N,) and Patras, Greece (38 degrees N). There was no significant effect of treatment on mass loss for samples collected after 2, 12 and 14 months decomposition at Amsterdam, or after 4 months decomposition at Adventdalen. Significant reductions in the mass loss of litter decomposing under elevated UV-B compared to ambient were found at the other 2 sites. The only effect of treatment on litter chemistry during decomposition was a significant reduction in the N concentration of material at Abisko and a significant increase in C:N at Patras for litter decomposing under elevated UV-B. Significant differences were found in the structure of the fungal community decomposing litter in Sweden, the only site to be tested. These data, and the few published studies of the response of decomposition to UV-B incident on litter suggest that, in the ecosystems and climates that have been studied, such direct effects are typically confined to the initial stages of decomposition, and are rather small in magnitude.