2023 Volume 28 Issue 1-2 Pages 13-23
To clarify the autonomous vegetation recovery and the extent of human impact after the severe disturbance caused by the Great East Japan Earthquake/Tsunami in March 2011, we investigated the vegetation, 10 growing seasons after the tsunami disturbance, along a coastal sand-dune ecotone of Sendai Bay, Japan. Vegetation surveys were carried out in August and September 2020 at 91 quadrats covering over the three-types of ecotone zones, (i.e., coastal herbaceous vegetation zone on backshore and sand dune, small Pinus thunbergia zone on sand dune and Pinus spp. plantation dominated zone on backswamp and beach ridge), each of which has consisted of various patches of natural sites (e.g., dry or wet bare sand habitats by deposition or peeling processes of tsunami) and artificial sites (e.g., embankment composed by hilly soils, temporally roads with rocks and sea walls built of concrete). Results of the NMDS ordination using the Jaccard similarity index calculated by the presence/absence of species showed that (1) communities established autonomously on natural sites were different among three types of ecotone zones, and that (2) especially in Pinus spp. plantation dominated zone, diversity of community was enhanced in wet bare sand site and remnant forest site, owing to invasion of submerged plants and survive of perennial herbs and woody plants as undergrowth. On the contrary, (3) similar community characterized by many exotic plant species appeared on the embankment regardless of ecotone zones, while a treatment covering by on-site sand promoted emergence of several coastal plant species. This study indicated that the conservation of natural habitats diversified along a coastal sand-dune ecotone and the vegetation rehabilitation technique such as a treatment covering by on-site sand on the embankments are effective in restoration of coastal vegetation and inhibition of exotic plant invasion.
