Variation and synchrony of tree species mast seeding in an old-growth temperate forest

Questions: Mast seeding, i.e. synchronous highly variable seed production among years, occurs in many perennial plant species and across diverse plant communities. Two predominant hypotheses for mast seeding are pollination efficiency and predator satiation, with weather conditions as a proximate cause. Little consensus has been achieved regarding the relative impacts of ultimate selection and proximate weather on variation in seed production. Moreover, mast-seeding studies often focus on a single species or phylogenetically closely related species, while studies on plant communities consisting of tree species with a diversity of reproductive strategies are less common. Location: A 25-ha Changbaishan temperate forest dynamic plot, northeast China. Methods: We used 8 yr of seed rain data to characterize patterns and evaluate underlying selective drivers of mast seeding. We employed generalized linear mixed-effects models (GLMMs) to analyse the relationships between inter-annual variability of mast seeding and weather conditions. Results: All 20 species in this forest community exhibited high variability in annual seed production, but the magnitude of seed production among species was generally asynchronous across years. Wind-pollinated species had higher inter-annual variation of seed production than animal-pollinated species, while species dispersed by seed predators and abiotic modes (e.g. wind and gravity) showed little variation. Species responded individually to weather conditions for both temperature and precipitation, and spring phenology in the same year as seed production had a larger effect among species than both the weather conditions of the same summer and season-long lags. Conclusions: Our findings suggest that pollination efficiency hypothesis had a much stronger effect than predation satiation hypothesis on mast seeding, and weather conditions demonstrated the proximate role of weather drivers in producing the community-wide mast-seeding pattern. We emphasize the need to simultaneously assess drivers of mast seeding for multiple species within a plant community.