Expansion of dwarf bamboo, Sasa nipponica, grassland under feeding pressure of sika deer, Cervus nippon, on subalpine coniferous forest in central Japan

Abstract

The long-term changes of the area of Sasa nipponica grassland, bark stripping damage to trees by sika deer, Cervus nippon, and sika deer densities on Mt. Ohdaigahara were assessed with aerial photographs, information from previous studies, and field experiments. The grasslands expanded year after year. The expansion rate was highest from 1982 to 1992, and lowest from 1992 to 1997. Bark-stripping damage on coniferous trees was heavier than that on broadleaf trees in both the early 1980s and 1998. The deer density in the eastern part of the area had been high (14.4-64.3 km -2 ) from 1984 until 1998. We presume that rich growth of S. nipponica and heavy feeding pressure by sika deer over the long term caused expansion of S. nipponica grasslands by killing canopy trees by bark stripping and preventing forest regeneration.

Establishment and growth of coniferous seedlings in an altered forest floor after long-term exclusion of deer

“…Nakai (Ide and Kameyama 1972). The average densities of sika deer on Mt Ohdaigahara from 1993 to 1999 were 17.5-39.5 km -2 (Maeji et al 1999;Ando et al 2006). S. nipponica is the main forage of sika deer in this area (Yokoyama et al 1996).…”

Effects of deer browsing on the survival and growth of Abies homolepis and Picea jezoensis var. hondoensis seedlings after fencing on Mt. Ohdaigahara

“…The average densities of sika deer on Mt. Ohdaigahara from 1993 to 1999 were 17.5-39.5 deer/km 2 (Maeji et al 1999;Ando et al 2006). Sika deer mainly forage on S. nipponica in this area (Yokoyama et al 1996).…”

Deer-proof fence prevents regeneration of Picea jezoensis var. hondoensis through seed predation by increased woodmouse populations

“…In 1996 and 1997, the population density of sika deer on Mt. Ohdaigahara was estimated to be 17.5-30.9 individuals km -2 (Maeji et al 1999); in 1999, this was 22.0 individuals km -2 (Ando et al 2006(Ando et al ), and in 2005(Ando et al and 2006 (after placement of the fence), 13.0-19.0 individuals km -2 (Goda et al, unpublished data). The eastern area is used more intensively by deer than the western area (Maeji et al 2000;Yajima et al 2002).…”

“…Until the 1980s, the eastern area was covered by dense coniferous forests. However, during the last 25 years overstory trees have been killed by deer debarking, and the forest-floor vegetation in and around this area has changed rapidly to open grassland dominated by S. nipponica (Yokota and Nakamura 2002;Ando et al 2006) because S. nipponica grows well in strong light (Kawahara and Tadaki 1978) and has a high tolerance to deer grazing (Yokoyama and Shibata 1998). In an attempt to preserve the forest in the eastern area of Mt.…”