Potential of soil seed banks in the ecological restoration of overgrazed floor vegetation in a cool-temperate old-growth damp forest in eastern Japan

Abstract

Damp forests are vulnerable ecosystems and have peculiar species compositions. Deer can cause severe damage to damp forest composition and structure. However, little is known about the effect of deer on soil seed banks of damp forests and the restoration potential of soil seed banks. I surveyed the compositions of the soil seed bank and floor vegetation both inside and outside a deer exclosure in an old-growth damp forest in eastern Japan using the seedling emergence method. Floor vegetation was composed of 71 % palatable and 1 % unpalatable species inside the exclosure but 6 % palatable and 83 % unpalatable species outside the exclosure. Forty-four species and 642 seeds m−2 germinated inside the exclosure, whereas 39 species and 985 seeds m−2 germinated outside the exclosure. Seed bank composition was 29 % palatable and 43 % unpalatable species inside the exclosure and 1 % palatable and 73 % unpalatable species outside the exclosure. Percentage similarity between the soil seed bank outside and the floor vegetation inside the exclosure was very low. These results indicate that the soil seed bank outside the exclosure has little potential to aid the recovery of floor vegetation. Conservation measures, such as deer exclosures and deer control, must be introduced before the floor vegetation is retrogressed by sika deer grazing.