SPATIAL AND SEASONAL PATTERNS OF SEED DISSEMINATION OF CORNUS-CONTROVERSA IN A TEMPERATE FOREST

Seasonal and spatial patterns of seed dissemination ofthe canopy tree Cornus controversa were studied over two fruiting seasons in a temperate deciduous forest in Japan. Seedfall was monitored every 2 wk in seed traps (N = 221) distributed over a 1-ha study plot that included 12 mature Cornus. Estimated annual seed production was 1.57 x 10(6) seeds/ha. In both years, the peak of fruit ripening had already ended before migratory frugivorous birds entered the area and only 17% ofthe seeds were disseminated by birds. Directly fallen seeds were deposited close to the parent trees (usually within 10 m, infrequently as far as 35 m from parent trees). In contrast, bird-disseminated seeds showed a markedly scattered distribution; the birds deposited more than half of the seeds they ate > 5 m from the crown edge, and density of bird-disseminated seeds exceeded that of directly fallen seeds at distances > 15 m, with some found > 40 m from the nearest mature Cornus. In addition, birds seemed to selectively eat fruits that contained viable seeds. The density of bird-disseminated seed decreased significantly with increasing distance from fruiting trees, both conspecific and heterospecific. Distance to the nearest edge of canopy gaps that were several years old had little effect on the spatial pattern of bird-disseminated seeds. This means that seeds of C. controversa were not directionally dispersed into canopy gaps by birds.