Abstract
The forest of Senjugahara area, Nikko national Park, was experienced a simultaneous death of dwarf bamboo caused by over grazing of Sika deer (Cervus nippon) around the middle of 1990s. Vegetation mapping was conducted in the area to clarify the distribution of forest floor vegetation established after the disappearing of dwarf bamboo. Major forest types of the surveyed area were Ulmus davidiana var. japonica forest, Quercus crispla forest, and Larix kaempferi artificial forest. Whole area of the Senjugahara was covered by Sasa senanensis or Sasamorpha borealis until the beginning of 1990s, however, they were replaced by different forest-floor types dominated by unpalatable herbaceous plants such as Aster ageratoides subsp. leiophyllus, Ligularia dentata, and Carex oxyandra. In addition, the forest-floor type with low vegetation cover was found in some part of the area. Dominant species of the present forest floor were not the original composition species of U. davidiana var. japonica and Q. crispla forest, because they didn't occur in the data obtained in 1970s. These species were presumed to expand into the forest from the surrounding open sites.
