桜島の昭和溶岩と大正溶岩における86年間の植生遷移 : 基質と種子供給源からの距離の影響

抄録

We studied the vegetation on the Showa and Taisho lava flows, which erupted from Mt. Sakurajima 54 and 86 years ago, respectively, and compared it with vegetation reported in earlier studies, with the aim of elucidating the primary succession. Anemochorous Pinus thunbergii was the most dominant species at all sites. The abundance of this species decreased from the margin to the center of the Taisho lava at a cross-section 2km wide. Age distribution study revealed that Pinus invaded from the margin to the center. Zoochorous broad-leaved species were more uniformly distributed between the margin and the center. Distance from a seed source seemed to be a limiting factor for Pinus but not for the broad-leaved species. There were two types of lava. One had a rough surface on which volcanic ash accumulated, and the other had large blocks with smooth surfaces. Pinus had similar dominance on both types, but broad-leaved species had difficulty invading the large blocks. As a result of these differences in seed dispersal and adaptability for each substrate, there were significant differences in vegetation distribution on lava flows of the same age.