Abstract
Kiritappu Mire in Eastern Hokkaido is designated as a national monument, a quasi-national park, and a Ramsar site, and it is one of Japan’s representative wetlands. Many of the marginal areas in the mire have been changed into lands for residence and fishery, thus the Kiritappu Wetland National Trust has been involved in the purchase of private lands, conservation, and restoration of the plants and animals in and around the mire. The organization started a wetland vegetation restoration project of a 0.4 ha site in April 2015 by removing layers of surface soil and sand which had been introduced as a kelp drying area. In this study, we revealed the vegetation succession of the restoration site from 2015 to 2021 and evaluated the effects of the restoration measure. We set up 42 plots with a dimension of 2 m×2 m in the restoration site and recorded the coverage of plant species every year except 2020. The mean overall coverage in the plots increased annually. The coverage in the final observation year considerably exceeded that of the adjacent control site （original vegetation） dominated by Carex lyngbyei. Dominant species in the restoration site have been replaced multiple times;Juncus bufonius and Juncus wallichianus were dominant in the first two years, Juncus decipiens, Juncus tenuis, and Trifolium repens in the next three years （3rd-5th）, and Juncus fauriei and Eleocharis kamtschatica f. kamtschatica in the final year （7th year）. The Bray-Curtis similarity index between the restoration and the control plots was extremely low with a value of 0.099 even in the final year. The dominance of Juncus species implied that the vegetation change in this restoration site was typical of early secondary succession in mires. The topsoil removal was effective for the regeneration of wetland vegetation in the site, but longer-term monitoring is needed to ascertain whether the restoration of the original vegetation is feasible.
