CIESIN Thematic Guides The majority of research on elevated UV-B impacts has been carried out in laboratory settings where climatic conditions can be controlled. Notable exceptions to this include field studies of certain agriculturally important species and coniferous trees. Teramura et al. (1991) outline both types of studies in the chapter "Terrestrial Plants" of the United Nations Environment Programme's (UNEP) Effects of Ozone Depletion.
Several studies have investigated the effects on agricultural crops. In a six-year field study at the University of Maryland, Teramura, Sullivan, and Lydon (1990) describe significant yield reductions of soybean under simulated ozone-depletion scenarios for one species, while another species appeared tolerant, in "Effects of UV-B Radiation on Soybean Yield and Seed Quality." Conversely, in "Growth and Yield of Field-grown Soybean in Response to Enhanced Exposure to UV-B Radiation," Sinclair, N'Diaye, and Biggs (1990) indicate no effect of enhanced UV-B on soybeans in a study conducted at the University of Florida. Teramura, Ziska, and Sztein (1991) report sensitivity of rice cultivars to UV-B was exhibited in certain species in "Changes in Growth and Photosynthetic Capacity of Rice with Increased UV-B Radiation." These studies also emphasize the impact that local microclimatic conditions can have on plant sensitivity to increased UV-B.
Indirect effects of UV-B on agricultural and other plant species have also been observed. Barnes, Flint, and Caldwell (1990) describe changes in morphology of wheat and wild oat species exposed to enhanced UV-B in "Morphological Responses of Crop and Weed Species of Different Growth Forms to Ultraviolet-B Radiation." These results suggest that UV-B enhancement may lead to a shift in competitive balance among certain species. Field studies with loblolly pine trees show decreased photosynthetic activity under simulated ozone depletion scenarios. Reductions in productivity ranged from 0 to 40 percent depending on seed sources and the age of tree needles. Other conclusions drawn from this study suggest UV-B may have a cumulative effect in the loblolly pine, resulting in reduced growth over the lifetime of the tree. Teramura and Sullivan (1991) review these effects in "Potential Impacts of Increased Solar UV-B on Global Plant Productivity." Rupert (1986) discusses plants' natural photorepair mechanisms, which could mitigate UV-B damage, in "Cellular Repair and Assessment of UV-B Radiation Damage."> These mechanisms, along with other factors such as temperature, precipitation, and availability of nutrients, are likely to modify the impacts of ozone depletion. As with many biological systems, further studies are required to gain a better understanding of all processes involved.
