Methodology for comprehensive evaluation of UV-B tolerance in trees

Decreasing stratospheric ozone concentrations have led to concern for an enhanced UVB radiation (wavelength range of 280-315 nm) reaching the Earth's surface. An understanding of the mechanism of UVB radiation tolerance and sensitivity may improve our ability to assess the potential effects of changes in solar UVB radiation on plant species. The purpose of this research was to conduct an assessment of tolerance of southern trees to future enhanced UVB radiation. This paper describes the systematic approach developed for such an assessment and the preliminary results associated with thirty-five broadleaf tree species in the South studied during two growing seasons. Results indicated that the diverse trees in the South possessed various biological characteristics in defense of UVB damage. It is suggested that the approach to comprehensive evaluation of UVB tolerance in diverse trees should focus on leaf optical properties, mainly depth of light penetration into leaves, leaf anatomical and morphological changes, and concentration of leaf UVB absorbing compounds during leaf development.