Effects of bark-stripping by Sika deer (Cervus nippon) on population dynamics of a mixed forest in Japan

The effects of tree bark-stripping by Sika deer (Cervus nippon) on populati on dynamics of forest trees were studied in a cool-temperate mixed forest i n Ohdaigahara, western Japan. Detailed observation of all trees greater tha n or equal to 2 cm in diameter at breast height in a 1 ha plot for 2 years showed that stems of Abies homolepis, Clethra barvinervis, Viburnum furcatu m, Stewartia pseudo-camellia and Ilex geniculata suffered serious bark-stri pping by deer. Smaller stems of A. homolepis were girdled all at once, and dead soon after that. Larger stems were bark-stripped Little by little, and did not die unless completely girdled. Stems of C. barvinervis and S. pseu do-camellia did not die soon after bark-stripping even if completely bark-s tripped. The tree population monitored in two 0.2 ha belt transects for 15 years demonstrated that the mortality of A. homolepis and V. furcatum has i ncreased consistently, especially in the last 5 years. In contrast, no tend encies were found for Fagus crenata, Pourthiaea villosa and Symplocos corea na; these species were seldom bark-stripped by deer. Recruitment rate in th e whole forest decreased in recent years. Thus the density of smaller trees decreased due to high mortality of bark-stripped species and low recruitme nt rate for all species. Though the bark of trees is less important as fora ge for deer than green forage such as dwarf bamboo, bark-stripping does mor e serious damage to trees than browsing on leaves and twigs because the inj ury by bark-stripping does not readily recover and kills considerably large trees. The ratio of canopy gap will be increased by browsing unless the de nsity of deer is reduced. Furthermore, bark-stripping accelerates the incre ase of canopy gap ratio. (C) 1999 Elsevier Science B.V. All rights reserved .