Correlates of interspecific synchrony and interannual variation in seed production by deciduous trees

Eastern deciduous forests are populated with a variety of hardwood species, with composition at large scales determined by a complex interplay of temperature, moisture, and disturbance. An understanding of seed production is important in the context of forest regeneration and wildlife management. We analyzed time series data obtained from the literature to investigate (1) the effects of life-history characteristics on interannual covariation in seed production; (2) the environmental drivers of interannual variation in seed production; (3) the effects of spatial relations on seed production. Life-history attributes accounted for between 9% and 29% of annual covariation in interspecific seed production. Phylogenetic similarity was an important determinant of covariation in seed production across species groups. Similarity in geographic range had a positive effect on covariation among oak species, but a negative effect on covariation among non-oak species. Weather accounted for 18.1% of the variation in seed production for oaks of the Lobatae section and 12.2% of the variation in seed production for oaks of the Quercus section. Climate was only significant for oaks of the Quercus section, with climate variables accounting for 14% of the variation in seed production. For two species, red and white oak, there was a significant east–west gradient in acorn production, possibly indicating the presence of a precipitation gradient. These results provide a comprehensive overview of seed production across eastern North America through time. # 2007 Elsevier B.V. All rights reserved.