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 tested for their rates of removal by seed predators in two remnant patches (15-20 ha) of old-growth temperate forest in Chiloe Island, southern Chile (47 degrees 30'S). Field assays were aimed at assessing the rates of post-dispersal seed consumption, mainly by rodents and understory birds. Assays were conducted in summer and early fall of 1996 and 1997. We investigated whether seed consumption differed among habitats, between seasons and among species differing in seed mass and abundance in the canopy of remnant parches. Trays 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 adjacent to pastures, forest interior (100 m away from any edge), and inside canopy gaps formed by tree falls. Overall, 7-65% of the seeds in experimental trays were removed by predators from 43 to 93% of all the trays within five days. Removal rates increased from mid-summer to tarry fall, presumably as a result of increasing density of birds and rodents. When seed removal rates differed among habitats. more seeds were taken from trays placed in forest interior than under canopy gaps. Forest margins had intermediate rates of seed removal. Marked differences in seed removal rates observed among species were unrelated to seed mass or plant species abundance. We conclude that season and habitat are the most important variables determining the intensity of seed predation in forest fragments. Seed predation rates recorded in live-day assays suggest that the regeneration of woody species, particularly in forest interior, may be affected by post-dispersal seed consumption by vertebrates.