DECREASE OF LARGE-BODIED DISPERSERS LIMITS RECRUITMENT OF LARGE-SEEDED TREES BUT BENEFITS SMALL-SEEDED TREES

Although it is well accepted that large-bodied predators exhibit higher seed handling ability than those with small body size, little is known about the ecological consequence of decrease of dispersers with large body size on the recruitment of large-or small-seeded trees. In this study, seed removal, seed dispersal, and seedling recruitment were investigated in two stands with different rodent composition (Apodemus peninsulae, Clethrionomys rufocanus, Tamias sibiricus, and Sciurus vulgaris) in temperate forests, northeast China. Our aim was to assess the ecological effect of loss of large-bodied rodents on seed removal and seedling establishment of five sympatric tree species (Pinus koraiensis, Quercus mongolica, Corylus mandshurica, C. heterophylla, and Juglans mandshurica). In the primary stand, where S. vulgaris with large body size are present, larger seeds or those with thicker seed hulls (seed coats) were more likely to be dispersed and cached, but smaller seeds and those with thinner hulls were more likely to be eaten immediately. When large-bodied disperser S. vulgaris are absent due to forest fragmentation and logging, larger seeds or those with thicker seed hulls were less likely to be dispersed and cached; however, smaller seeds and those with thinner hull gained more opportunities to be cached. The presence of large-bodied dispersers benefited the seedling establishment of large-seeded species but not small-seeded ones. In contrast to the conventional studies, our results show that small-seeded trees gained an opportunity to survive and establish seedlings with the loss of large-bodied rodent species in the fragmented forests.