GNAWING DAMAGE BY RODENTS TO THE SEEDLINGS OF FAGUS-CRENATA AND QUERCUS-MONGOLICA VAR GROSSESERRATA IN A TEMPERATE SASA GRASSLAND DECIDUOUSFOREST SERIES IN SOUTHWESTERN JAPAN

The effects of dwarf bamboo, Sasa, cover On the initial mortality of h ardwood seedlings were investigated by transplanting 1-year-old beech (Fagus crenata) and current-year oak (Quercus mongolica var. grosseser rata) seedlings to three different stands; old-growth beech and second ary oak forests with Sasa undergrowth, and a Sasa grassland in a grass land-forest series near the top of Mt Jippo, southwestern Japan. The m ost frequent cause of seedling mortality was gnawing of the stems by r odents. Tn the beech forest, the gnawing was more likely to occur unde r Sasa cover, suggesting that it provides a good habitat for rodents o n the beech forest floor. The Sasa undergrowth may thus play an import ant role in regeneration of beech forest. In the oak forest, mortality of both species was low and only a little gnawing occurred during a y ear. However, no natural oak seedlings were found in the forest even a fter a mast year. This may be because most of the acorns disappeared b efore establishment. The early-stage demography of hardwood seedlings such as oak may thus play an important role in regeneration of oak for est. In the Sasa grassland where the seed supply is small, almost all of the seedlings died from gnawing regardless of the presence of Sasa cover. These factors prevent the recruitment of a sizable seedling ban k. Rodents may thus play an important role in maintenance of the Sasa grassland.