Elevated UV-B radiation effects on experimental grassland communities

Experimental grassland communities (turves) were exposed to supplemental le vels of UV-B radiation (280-315 nm) at an outdoor facility, under treatment arrays of cellulose diacetate-filtered fluorescent lamps which also produc e UV-A radiation (315-400 nm). Control treatments consisted of arrays of po lyester-filtered lamps, which allowed for exposure to UV-A radiation alone, and arrays of unenergized lamps allowing for exposure to ambient levels of solar radiation. Turves were placed in the experimental facility immediately after sowing (i n April) with six species typical of an MG7 Lolium perenne-Plantago lanceol ata grassland and were cut twice during the growing period (13 and 25 weeks ) and harvested destructively at the end of the experiment (71 weeks). At h arvest, total biomass was separated into each of the six species originally sown in the experimental turves and other species (those not originally so wn in the turves). Only one significant effect of treatment on biomass was recorded; Lolium pe renne showed a significantly higher biomass under enhanced UV-B than under ambient radiation during the early stages of growth. Otherwise no significa nt effects of treatment were found at any of the three harvests on either t he biomass of the individual species sown in the turves, or on the total co mbined biomass per turf. Large variances in the data from each block and lo w replication (4 blocks) resulted in poor statistical power in the data ana lysis, with the exception of the significant effect referred to above. Alth ough species composition within the turves changed over time, there were no significant differences in species ranks between the three treatments at e ach harvest.