Synchronized annual seed production by 16 principal tree species in a temperate deciduous forest, Japan

To investigate synchronized annual fluctuation of seed production and its advantage for regeneration at the community level, for nine years (1987-1995) we monitored the flowering, seed production, and seedling emergence of the 16 principal tree species in a temperate deciduous forest, Ogawa Forest Reserve, in central Japan. We found that the species with higher synchronized flowering within a population had larger fluctuation of annual seed production at the population level. The coefficient of concordance of flowering and the coefficient of variation of annual seed production were continuously distributed among species, making it difficult to distinguish masting from nonmasting species. The annual seed production patterns of the 16 species were classified, by cluster analysis, into groups that synchronize their fluctuation of annual seed production. This analysis showed a highly synchronized annual seed production, not only among congeneric species, but also among species of different families. Although our results have some insufficiency of statistical significance, they did show that predator satiation, both in a population and a guild, effectively operated for many species to enhance seed survival at the pre-dispersal stage. They also showed that pollination efficiency was likely to be operating at the population level for half of the wind-pollinating species. However, generalist predator satiation at the postdispersal seed stage may not operate in a simple, detectable manner in this species-rich forest community. It is highly probable that there are combined effects of several factors: limited weather triggers for flowering, common flowering physiology among taxonomically related species, and the ecological advantages at the population and guild levels, may cause multiple species to have synchronized fluctuation patterns of seed production.