Abstract / Introduction / Summary:
We compared the plant species diversity of evergreen broadleaved forests, cedar plantations, and pioneer communities on pyroclastic flow sites on Kuchinoerabu Island and Yakushima Island, and evaluated the effects of deer feeding. On both Yakushima and Kuchinoerabu Islands, species density in cedar plantations tended to be lower than in evergreen broadleaved forests, and the species density of perennial herbs tended to be lower than that of other plant life forms. At the pyroclastic flow site on Kuchinoerabu Island, ferns had the highest species density, followed by shrub species. Ferns and shrubs together accounted for approximately 80% of the relative dominance, while the number of tall tree species, which are the main components of evergreen broadleaved forests, was very low. On the other hand, the relative dominance of unpalatable plants was significantly higher in cedar plantations on both islands. However, their species density was not greater than in evergreen broadleaved forests; instead, it was similar or even lower. This suggests that the diversity of unpalatable plants does not increase as forage plants decline. Instead, certain unpalatable plants thrive and dominate in the understory of cedar plantations. In addition, the relative dominance of forage plants declined even further at the pyroclastic flow site. Deer feeding may have hindered the renewal of forage plants during the creation and management of cedar plantations, as well as during vegetation recovery from pyroclastic flow disturbance. This could have altered the vegetation succession sequence.
