Vertical seed dispersal toward higher or lower altitudes has recognized as one of the critical processes for plant escape from climate change. Nevertheless, studies exploring vertical seed dispersal are very scarce, preventing the prediction of future vegetation dynamics. By using the oxygen isotope ratio of seed, we previously evaluated the vertical seed dispersal of summer fruiting cherry (Cerasus leveilleana) and autumn fruiting kiwifruit (Actinidia arguta) by mammals in Kanto Mountains, central Japan. The results were contrasting: while seeds of cherry were dispersed toward mountain tops, seeds of kiwifruit were dispersed toward the foot of mountains. These were probably because mammals followed plant phenology in the temperate zone which proceeds from the foot to the top of mountains in spring to summer and from the top to the foot in autumn to winter. However, is this seed dispersal pattern commonly observed in other mountains where topography and frugivore composition are different? How about seed dispersal by birds? To answer the questions, we evaluated vertical seed dispersal of one summer fruiting and one summer-to-autumn fruiting cherry species (C. leveilleana and Padus grayana, respectively) in Ashio Mountains and Abukuma Highlands in central Japan. We evaluated seed dispersal by mammal and bird, by using the oxygen isotope ratio of dispersed seeds in their feces.
Results/Conclusions
We found strong uphill seed dispersal of summer fruiting cherry, and weak downhill seed dispersal of summer-to-autumn fruiting cherry, irrespective of mountains. The difference in vertical seed dispersal distance among animals, that is, bears, macaques, raccoon dogs, martens and birds was not clear. We also found that bears intensively dispersed seeds vertically. Our results were consistent with the previous studies and supports the idea that plant phenology can be a deterministic factor of vertical seed dispersal by animal in the temperate zone. While uphill seed dispersal helps plant escape from global warming, downhill seed dispersal prevents such escape. Considering that many of trees depend on animals for seed dispersal and fruit in autumn to winter, forest composition in the temperate zone may change under global warming due to the biased vertical seed dispersal by animal.