Impact of large-scale anthropogenic disturbance on litter decomposition and forest-dwelling amphibians through changes in dwarf bamboo traits

This study investigated the effects of large-scale forestry disturbance on litter decomposition and forest-dwelling organisms. Specifically, we focused on changes in Sasa kurilensis litter following soil scarification and assessed whether such modifications affect litter decomposition dynamics over a 50-year period in Japan. Additionally, we reared larvae of Hynobius retardatus, a forest-dwelling salamander endemic to Hokkaido, in Sasa kurilensis leachate to evaluate the effects of plant trait changes on the salamander. Our results showed that, following soil scarification, the concentration of phenolic compounds in young dwarf bamboo leaves and leaf litter was higher in scarified areas than in untreated control areas. As phenolic compounds function in plant defense, their elevated production likely reflects a defensive response to disturbance. This effect persisted for several decades but mostly disappeared after 50 years. Decomposition experiments using dwarf bamboo litter collected from soil sites that had undergone scarification 10 and 50 years previously revealed that litter from the 10-year scarified site decomposed more slowly than that from the control site, whereas no significant difference in decomposition rates was observed between treatments at the 50-year site. These findings indicate that large-scale forestry disturbances can influence litter decomposition for decades via increases in litter phenolic levels. Additionally, the growth rate of H. retardatus larvae reared in litter leachate was slower at the 10-year scarified site than at the control site. While the specific constituents affecting larval growth were not identified, changes in litter traits likely played a role.