Seed rain and seedling establishment of the dioecious tree Neolitsea sericea (Lauraceae): effects of tree sex and density on invasion into a conifer plantation in central Japan

Abstract

We studied the effects of differences in parent sex and density on seed rain and seedling and (or) sapling recruitment in a dioecious tree species (Neolitsea sericea (Bl.) Koidz.) with bird-dispersed seeds. We established four microhabitats: male or female trees inside or outside a single patch. The density of bird-disseminated seeds was significantly higher beneath females and inside the patch than beneath males and single trees outside the patch; this led to higher density of emerged seedlings inside the patch. The survival rate of germinated seedlings was also higher inside the patch than below single trees. In contrast, the survival rate of saplings was highest beneath males outside the patch, although very few seeds are dispersed beneath single males. Seedling and sapling recruitment beneath females and inside the patch will be accelerated owing to higher density of dispersed seeds, high seedling survival, and greater sapling density. In contrast, recruitment beneath males will be very slow. However, microhabitats beneath males are probably more suitable for seedling and sapling recruitment than microhabitats beneath females, since the survival rate of saplings was higher beneath males. Parental sex-biased seed rain and seedling and (or) sapling recruitment in dioecious plants may explain the regeneration pattern at a local scale.