This chapter reports the phenological trends (reproductive and vegetative events) of some early spring and late winter flowering trees all around the world and especially Europe: Corylus avellana L. (hazel); Quercus robur L. (common oak); Quercus ilex subsp. ballota, (Desf.) Samp. (holm oak); Betula spp. (birch); Salix alba L. (willow); Fraxinus angustifolia Vahl. (ash); and Morus alba L. (white mulberry). They are deciduous and perennial trees growing in different climatic areas of Europe. They have anemophilous pollination liberating huge pollen concentrations to the atmosphere. Aerobiological surveys give us reproductive phenological information of these wind-pollinated species. The phenological response to climate during the last years was analysed, including budburst, leaf unfolding, flowering, fruit ripening, fruit harvesting, leaf colour change, and leaf fall. The response of each taxon to climate was different; most of the revised species and sites presented an advance of the early spring phenophases, especially budburst. On the contrary, some studies detected a delay in autumn vegetative phases, especially leaf fall events. The statistical analyses indicated that phenological advances are a consequence of the increasing temperature trend—minimum temperature being one of the most influential factors. The increase of temperature influenced that leaf unfolding and flowering dates showed a general advance expressed by negative correlations with temperature data, whereas the leaf colour change and leaf- fall presented positive correlations due to the delay of the colder temperatures. The phenological revised results can be considered as reliable and valuable bio-indicators of the impact of the recent climate change in the Northern Hemisphere, and especially Central and Southern Europe.
Part of the book: Plant Communities and Their Environment