西南日本の江田島における山火事後20年間の遷移過程と種組成 Species composition through twenty years post-fire succession on Etajima Island, southwestern Japan
Species composition in 20 years post-fire succession on Etajima Island, southwestern Japan was investigated in five 100m^2 permanent plots based on phytosociological analysis. Twenty plant species that regenerated from sprouting organs and burned stem bases a year after the fire, consistently developed in 20 years. Therophytes such as Erigeron sumatrensis, Crassocephalum crepidioides, and Erechtites hieracifolia predominated the area and were found only in year 1. Among the invading plant species, hemicrypthophytes dominated in the shrubby stage before the young pine forest started to develop. Establishment of herbaceous plants prevailed during the shrubby stage and thereafter, the growth of such woody species as nanophanerophytes, microphanerophytes, and mesophanerophytes was improved. The diversity index of vegetation increased linearly after the fire and peaked in year 4. The index continued to rise and reached the maximum when the tree layer was developed. Seedling emergence and establishment of Pinus densiflora in the subtree layer was comparatively late compared to other broad-leaved trees. However, the susceptibility of pines to disturbance, such as fire, and their tolerance to nutrient deficient soils allowed them to enlarge their crowns and started to enter the tree layer in year 18. There was no temporal variation on the cyclic regeneration of pine forest in the area two decades after the fire. This could be traced to the frequency of fire in the region occurring in spring where pines susceptibility to fire is high due to their low foliar moisture content.
植生学会誌 20(1), 17-30, 2003