An assessment of post-dispersal seed predation in temperate rain forest fragments in Chiloe Island, Chile

Seeds of seven tree species. sis shrub species, and one epiphyte were teste d for their rates of removal by seed predators in two remnant patches (15-2 0 ha) of old-growth temperate forest in Chiloe Island, southern Chile (47 d egrees 30'S). Field assays were aimed at assessing the rates of post-disper sal seed consumption, mainly by rodents and understory birds. Assays were c onducted in summer and early fall of 1996 and 1997. We investigated whether seed consumption differed among habitats, between seasons and among specie s differing in seed mass and abundance in the canopy of remnant parches. Tr ays containing 20 seeds each, 6 8 replicate trays per species and habitat, were placed in the forest floor in each of three habitats: forest edges adj acent to pastures, forest interior (100 m away from any edge), and inside c anopy gaps formed by tree falls. Overall, 7-65% of the seeds in experimenta l trays were removed by predators from 43 to 93% of all the trays within fi ve days. Removal rates increased from mid-summer to tarry fall, presumably as a result of increasing density of birds and rodents. When seed removal r ates differed among habitats. more seeds were taken from trays placed in fo rest interior than under canopy gaps. Forest margins had intermediate rates of seed removal. Marked differences in seed removal rates observed among s pecies were unrelated to seed mass or plant species abundance. We conclude that season and habitat are the most important variables determining the in tensity of seed predation in forest fragments. Seed predation rates recorde d in live-day assays suggest that the regeneration of woody species, partic ularly in forest interior, may be affected by post-dispersal seed consumpti on by vertebrates.