Effects of light and forest floor conditions on the initial phase of regeneration of Pinus denstiflora Sieb, et Zucc. in pine wilt disease forests

We attempted to induce regeneration by seeding in a red pine forest damaged by pine wilt disease. Two red pine forests, were selected in Okayama Prefecture, one damaged and one not damaged, from which a total of five plots were selected. The rate of seed predation, the processes of emergence and growth, and the survival rate of seedlings of Pinus densiflora Sieb. et Zucc. were examined under a range of upper and lower level foliage density and conditions at the forest floor. The ratios of survival to emergence were higher in the damaged forest than in undamaged forest in which upper and lower foliage densities were high, or where the undergrowth had not been cut. Seedling growth was greater in the damaged forest than undamaged one. In terms of forest floor treatments, emergency, survival rate and seedling growth were higher when the litter and organic layer was removed than when the litter and organic layer remained. We believe that pine wilt disease, and the subsequent reduction in foliage density, increases light intensity at the forest floor, and that this supports seedling development, at least in the early growth stage. We conclude that regeneration of forests affected by pine wilt disease is possible.