Effects of ambient UV-B radiation on the above-ground biomass of seven temperate-zone plant species

Variations in the amount of solar ultraviolet-B radiation (UV-B) reaching the biosphere may alter productivity in non-agricultural plants. We examined how ambient levels of UV-B modify the biomass of seven temperate-zone species including three grass species (Echinochloa crusgalli, Setaria faberi, Elymus virginicus), three forbs (Verbascum blattaria, Lactuca biennis, Oenothera parviflora), and one tree species (Quercus rubra). Plants were grown outside in enclosures near Morgantown, WV, USA (39 degrees N, 79 degrees W) for one season under near-ambient or no UV-B conditions. The different levels of UV-B were achieved using filters which differentially transmit UV-B irradiance. There was a trend towards reduced above-ground biomass in L. biennis (14%) and significantly increased above-ground biomass in O. parviflora (10.2%) under ambient UV-B. The partitioning of biomass between individual plant parts was altered by ambient UV-B in O. parviflora. Leaf biomass was significantly increased (18%), and there were trends toward increased stem (6.7%) and reproductive (9%) biomass. In addition to biomass stimulations, O. parviflora grew significantly taller (5.3%) under ambient UV-B. This study provides evidence that some non-agricultural plants exhibit species-specific growth responses to variable UV-B, with short-lived forbs appearing to be the most sensitive. If the biomass and morphological alterations observed for the forbs in this study were to persist over several years, they might modify population dynamics, competitive interactions, and productivity in ecosystems as UV-B levels fluctuate in the future.