Little is known about the impact of vapor emitted from cooling towers on vegetation around geothermal power plants. In this study, the growth status of Fagus crenata saplings, placed at the site with different concentration levels of hydrogen sulfide (H2S) emitted from volcanic gas fumaroles, was confirmed by visual observation of leaves and branches and by a vegetation index (NDVI) calculated from multispectral images. The results showed that during the four-month experimental period from late May to mid-September, the onset of leaf necrosis and a decrease in the vegetation index was observed at the site with the highest H2S concentration. This was considered an effect of H2S absorbed by the leaves of the saplings, due to the high sulfur content in the leaves. On the other hand, no detrimental signs on the leaves were observed at sites with similar H2S exposure conditions to those around geothermal power plants, suggesting that the concentration levels of H2S measured around geothermal power plants have no impact on vegetation. No detrimental signs on the leaves were also observed for the trees naturally grown around fumaroles, even at the sites with higher H2S concentrations than those around geothermal power plants. This result suggests that the trees naturally grown in the local environment may be more tolerant to H2S than the saplings used in the experiment because they might have already obtained the form suited to the higher H2S concentrations.
