Early Stages of Regeneration after Fire in a Sugi (Cryptomeria japonica D. Don) Forest in Kiryu City, Gunma Prefecture

Abstract

Vegetation recovery in a 19-year-old sugi (Cryptomeria japonica D. Don) forest was investigated for the first three after fire in Kiryu city, Gunma prefecture, northern Kanto district. Stephanandra incisa, Lespedeza bicolor yar. japonica, Oplismenus undulatifolius, Macleaya cordata, Miscanthus sinensis or Rubus microphyllus were the dominant species through the three years. Increase ratios of SDR_3 of R. microphyllus or S. incisa also declined in the thrid year, while some species such as M. sinensis, M. cordata and Pueraria lobata had high rate of increase in SDR_3 also in the thrid year, and the former two dominated next to L. bicolor var. japonica in the thrid year. The aboveground biomass of the study site had been increasing rapidly year by year, and that of the thrid year was seven times more than that of the first year. The species originating from the buried seeds such as L. bicolor var. japonica, M. cordata or Mallotus japonicus were the most important species contributed to the increase of the biomass. Numbers of species decreased in the second year while vegetation cover amounted to 100% in the year. MORISITA'S Cλ(ρ) between the study site and adjacent unburnt forests had been decreasing year by year. Many species migrated in the study site and made a high diversity community in the first year. While a few species increased in SDR_3 repidly and the degree of succession also increased in the second year, some species disappeared and the number of species decreased. Accordingly the diversity of the community changed into lower in the year. Though the number of species in the thrid year was about hte same as in the second year, it became a greater difference of SDR_3 among species, and consequently, the diversity of the community decreased further. The community will be expected to continue for the present in the condition that many dominant species will change one after another.