Temporal pollen pattern in temperate trees: expedience or fate?

European forests are populated with a variety of wind-pollinated tree species. Their pollen productivity and spatio-temporal pattern are largely unknown. Long-term data (17 years) collected at 22 sites across Austria were presented and the pollen production of 12 tree genera was analysed. We ranked the tree genera according to their pollen productivity taking actual tree abundances of the Austrian Forestry Inventory into account. The productivity varied strongly among tree genera with a maximum for Betula. Pollen production in Larix, Abies and Picea amounted to approximately 1/20, while in increasing order Salix, Quercus, Alnus, Populus and Fraxinus produced approximately 1/3 to 1/4 of the respective Betula estimate. In general, pollen quantity in broadleaves was higher than in conifers. We analysed the temporal pollen production pattern by means of hierarchical cluster analysis and identified three major groups: [(Fagus, Larix, Picea, Abies), (Alnus, Betula, Fraxinus)], [Carpinus],[Populus, Salix, Pinus, Quercus]. Distance matrices based on life-history traits as well as molecular phylogeny were also constructed; they correlated significantly with each other by means of Mantel-tests. However, there was no significant relationship between the distances on temporal pollen production with the other matrices. Intermittent or idiosyncratic pollen production was studied by means of deviation from expected means, skewness and spindle diagrams. We proposed that Fagus, Carpinus, Larix, Picea and Abies belong to masting pollen producers, while the remaining genera idiosyncratically produced pollen over the monitored period. Moreover we correlated the distance matrix of pollen production for each tree genus at each sampling site with respective ecological distance matrices based on aerial and altitudinal distance among sites. Significant correlations were detected for tree genera (Fagus, Larix, Picea) which were also prone to pollen masting, thus indicating a Moran effect.