Leaf litter effects on seed and seedling predation of the palm Astrocaryum murumuru and the legume tree Dipteryx micrantha in Amazonian forest

The amount of leaf litter fall produced by different tree species in tropical forests varies in space and time. Falling litter may cover seeds and thereby enhance their survival by making their detection by seed predators more difficult. Tests were made to determine whether Astrocaryum murumuru and Dipteryx micrantha seeds survive better in microsites covered by leaf litter. Seed numbers and litter cover on the forest floor were experimentally manipulated. How natural variation in leaf litter cover and thickness affects seed and seedling survival of these two plant species was also examined. Seed survivorship was significantly higher for both plant species in microsites with leaf litter than in those with bare soil. Results from an experiment in which the litter was not disturbed showed that Astrocaryum seed survival was positively correlated with litter thickness (defined as the number of overlying dead leaves). Astrocaryum seedling survival was also significantly affected by leaf litter; more seedlings survived in shallow litter. Leaf litter had no effect on Dipteryx seedling survival. The results of the study suggest that early recruitment of both Astrocaryum and Dipteryx is influenced by the spatial distribution and amount of forest leaf litter.