Abstract
Diverse effects of sika deer are evident in the forest vegetation of the Chichibu Mountains. The cover of the lowest level of understory plants in the riparian forest of Nakatsugawa in the Chichibu district of Saitama prefecture was over 90% in 1983, but had decreased to only 3% by 2004. Plant cover values of only 1% were common in the early years of the current century. Toxic plants, including Scopolia japonica, were notable exceptions to the general decline in forest floor vegetation. The decreases in plant populations are likely to be related to sudden increases in deer population density detected after 2000 by cervid researchers in this area. Plants that remain after heavy grazing tend to be diminutive and have short growing seasons. It is, therefore, likely that, in addition to reducing overall vegetation cover, the deer are responsible for shifts in plant growth forms and life cycles.
