Ecological importance of ambient solar ultraviolet radiation to a sub-arctic heath community

摘要

While there is considerable knowledge of the effects of enhanced levels of ultraviolet radiation (UV) on plant species, much less is known of the importance of ambient levels of solar UV, particularly on natural plant communities. Effects of ambient solar UV radiation on a natural sub-Arctic heath community were investigated in a three year UV exclusion experiment in northern Sweden (68degreesN). UV transparent and UV opaque (excluding < 400 nm) plexiglas screens were placed over vegetation for three years to determine ambient solar UV effects on growth, reproduction and phenology of the three dominant dwarf shrub species, Vaccinium uliginosum, V. vitisidaea and Empetrum hermaphroditum. Additionally, effects of ambient solar UV radiation on leaf protection from UV-B were assessed through measurements of leaf UV-B absorbing compounds. Flowering and berry production by V. uliginosum were greatly increased (by five and 15 fold) in plots receiving ambient solar UV compared to those where solar UV had been excluded for three years. However, solar UV had no effect on stem growth, senescence and cover of the dwarf shrub species studied. It was therefore concluded that sub-Arctic dwarf shrubs are generally tolerant of ambient solar UV. Counterintuitively, ambient solar UV radiation reduced the levels of UV-B absorbing compounds in both Vaccinium species suggesting a reduction in protection provided. This indicates that measurements of leaf UV-B absorbing compounds do not necessarily provide a good indicator of plant tolerance to UV.