Investigating the Relationship between Plant Species Composition and Topography in the Tomeyama Landslide: Implications for Environmental Education and Sustainable Management in the Happo-Shirakami Geopark, Japan

The Tomeyama landslide in the Happo-Shirakami Geopark, Japan, has interesting and important geomorphological and geoecological characteristics. Understanding these characteristics is crucial for environmental education and sustainable management in the geopark. In this study, we quantified the characteristics of the landslide, including its precise topography and vegetation. We used high-resolution 2.5 m-mesh ALOS World 3D topographic data to define the topography of the landslide. We also surveyed plant species composition and cover in four plots (three on the upper slope and one on the convex lower foot slope), each measuring 20 m × 20 m. Our findings reveal that the landslide is sited on a northwest-facing slope, 250 m below the ridge top, and has a horseshoe-shaped main scarp with a height of 40 m. Two smaller secondary scarps and their corresponding displaced landslide blocks suggest reactivation since the main landslide event. In the upper slope plots, 40–55 plant species were identified, including 14–16 species associated with the Japanese beech forest and 2–5 species related to the Pterocarya rhoifolia forest. In the lower slope plot, 70 plant species were identified, including 14 species from the Japanese beech forest and 11 from the Pterocarya rhoifolia forest. The upper slope plant community belongs to the Japanese beech forest; however, categorizing the lower slope community is challenging, although more Pterocarya rhoifolia forest species are present compared with the upper slope. These results suggest that certain plant species have adapted to the diverse topography created by the landslide. These findings improve the understanding of landslide topography and plant community composition with respect to environmental factors and thereby support effective environmental education and sustainable management in the Happo-Shirakami Geopark.