The dioecious Populus tremula displays interactive effects of temperature and ultraviolet-B along a natural gradient

Abstract

Observed and projected warming has provoked research interest on tree phenology in relation to climate. While both ultraviolet-B (UV-B) radiation and warming has been shown to affect growth and development in plants, the combined effects of the two environmental factors has been little studied. In addition, there is concern for environmental change yielding divergent responses between sexes in dioecious tree species. Here, we present a study of the dioecious Populus tremula grown along a natural temperature and UV-B gradient in Central Norway, reducing UV-B using specific screening filters. We tested for effects on growth, timing of terminal bud formation and bud break, carbon and nitrogen content and concentrations of phenolic compounds. Increased elevation had a negative effect on plant growth and promoted bud formation, with effects differing between plant sexes. UV-B attenuation delayed bud formation and enhanced growth of males at the highest elevation, counteracting the effect of low temperature. In addition, elevation and UV-B affected concentrations of different phenolics in stems and leaves. Our data show that interactive effects of warming and other climate factors like UV-B should be considered when predicting climate change effects in woody plants, and add to present evidence of sex-related responses to climate change in dioecious woody plants.