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 population dynamics of forest trees were studied in a cool-temperate mixed forest in Ohdaigahara, western Japan. Detailed observation of all trees greater than 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 furcatum, Stewartia pseudo-camellia and Ilex geniculata suffered serious bark-stripping 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. pseudo-camellia did not die soon after bark-stripping even if completely bark-stripped. 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 increased consistently, especially in the last 5 years. In contrast, no tendencies were found for Fagus crenata, Pourthiaea villosa and Symplocos coreana; these species were seldom bark-stripped by deer. Recruitment rate in the whole forest decreased in recent years. Thus the density of smaller trees decreased due to high mortality of bark-stripped species and low recruitment rate for all species. Though the bark of trees is less important as forage for deer than green forage such as dwarf bamboo, bark-stripping does more serious damage to trees than browsing on leaves and twigs because the injury by bark-stripping does not readily recover and kills considerably large trees. The ratio of canopy gap will be increased by browsing unless the density of deer is reduced. Furthermore, bark-stripping accelerates the increase of canopy gap ratio. (C) 1999 Elsevier Science B.V. All rights reserved.