Investigating the Relationship between Plant Species Composition and...

[Full title: 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]

Citation: Tsou, C.-Y.; Yamagishi, H.; Kawakami, R.; Tsai, M.-F.; Miwa, T 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 Sustainability 2023 , 15 , 16572 https://doi.org/10.3390/ su 152416572 Academic Editor: Grigorios L. Kyriakopoulos Received: 22 September 2023 Revised: 22 November 2023 Accepted: 1 December 2023 Published: 5 December 2023 Copyright: © 2023 by the authors Licensee MDPI, Basel, Switzerland This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/) sustainability Article 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 Ching-Ying Tsou 1, * , Hiroki Yamagishi 2 , Reona Kawakami 3 , Mei-Fang Tsai 4 and Takuma Miwa 5 1 Faculty of Agriculture and Life Science, Hirosaki University, Aomori 036-8561, Japan 2 The Shirakami Research Center for Environmental Sciences, Faculty of Agriculture and Life Science, Hirosaki University, Aomori 036-8561, Japan; hyama@hirosaki-u.ac.jp 3 United Graduate School of Agricultural Sciences, Iwate University, Morioka 020-8550, Japan; u 3323004@iwate-u.ac.jp 4 Faculty of Education, Hirosaki University, Aomori 036-8560, Japan; jes 1362@gmail.com 5 Happo-Shirakami Geopark Promotion Council, Akita 018-2502, Japan; happosirakami.geo@gmail.com * Correspondence: tsou.chingying@hirosaki-u.ac.jp Abstract: 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 3 D 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 Keywords: landslide; morphometric parameter; environmental education; sustainable management; Happo-Shirakami Geopark 1. Introduction The intricate interplay of geological processes, ecosystem dynamics, and anthropogenic activities influences the landscapes that humans inhabit. Of these dynamic interactions, landslides have emerged as captivating phenomena that offer a distinctive lens into the interplay between Earth’s processes and the delicate equilibrium of its ecosystems [ 1 ]. For instance, within landslide regions, intricate and diverse terrain features with unique slope configurations, soil compositions, and moisture conditions contrast with those of the surrounding landscape [ 2 , 3 ]. The elaborate terrain features of landslides, which are Sustainability 2023 , 15 , 16572. https://doi.org/10.3390/su 152416572 https://www.mdpi.com/journal/sustainability

Sustainability 2023 , 15 , 16572 2 of 14 characterized by intricate undulations and complexities, are thought to facilitate the colonization of diverse forest plant species [ 4 – 6 ]. The ecological milieu of landslide areas showcasing these distinct attributes has the potential to function as educational material for environmental instruction, encouraging an appreciation of natural surroundings and conservation consciousness. Moreover, these attributes have implications for the integration of environmental education and sustainable management practices Efforts in environmental education related to landslides have focused predominantly on highlighting their geomorphological and geological formation processes [ 7 ]. Furthermore, some initiatives have involved the preservation and utilization of the landforms sculpted by landslides or the remnants of structures impacted by such events [ 8 ]. Exemplary cases include sites that showcase intricate geological and geomorphic formation processes, such as the establishment of a geological and landslide museum in Civita di Bagnoregio, Italy [ 9 ], as well as field-based educational endeavors along the Dorset and eastern Devon coasts in England [ 10 , 11 ] and within the Picos de Europa National Park in Spain [ 12 ]. Moreover, sites preserving the effects of human-induced landslides, such as the Vajont landslide in Italy [ 8 ], the Chiu-fen-erh-shan landslide following the 1999 Chi-Chi earthquake in Taiwan [ 13 ], and the Aratozawa landslide triggered by the 2008 Iwate–Miyagi inland earthquake in Japan [ 14 ], together with their associated structures, have been considered instructive examples. However, there are limited cases in which the relationship between plant species composition and terrain characteristics in landslide areas has been incorporated actively into on-site educational approaches This study was conducted in the Tomeya landslide, situated in the Happo-Shirakami geopark, Japan (Figure 1 a,b). It is worth noting that there is an existing research gap concerning the comprehensive investigation of plant species composition and topography in the study area. The primary objective of the study was to investigate the relationship between plant species composition and the topography of this landslide. In addition, the study considers the implications of the findings for environmental education Sustainability 2023 , 15 , x FOR PEER REVIEW 3 of 15 Figure 1. Maps and photograph of the Tomeyama study area, showing the location, topography, and geology ( a ) Location map (modified from the GSI Tile published by the Geospatial Information Authority of Japan) ( b ) NE ‐ oriented photograph of the Tomeyama landslide ( c ) Topography of the Tomeyama landslide (modified from the 1:25,000 scale topographic map published by the Geospatial Information Authority of Japan) The representation of the landslide scarp and displaced block is from [15] ( d ) Geological map of the study area (from [16]) 2. Study Area The Tomeyama landslide is located on a gentle slope of the Shirakami mountains, where 13% of the area has been designated as a Natural World Heritage site The landslide spans an elevation of approximately 150–250 m (Figure 1 c) Determining the timing and the driving factor behind the landslide occurrence is challenging due to the scarcity of historical records in and around the study area The geology of the Tomeyama landslide comprises a lower layer of Late Miocene to Early Pliocene mudstone and an upper layer of andesite and its associated pyroclastic rock (Figure 1 d) [16] The andesite volcanic event has a history eruptions dating back to 6.6 Ma [17] Vegetation in the study area consists of a cool ‐ temperate deciduous broad ‐ leaved forest, composed mainly of Siebold’s beech ( Fagus crenata ) and Pterocarya rhoifolia. The average annual rainfall in Happo town from 1991 to 2020 was 1501.6 mm; the largest monthly total rainfall occurred in July (172.2 mm) and the smallest in February (68.9 mm) [18] The forest around the Tomeyama landslide has been protected from logging since the Hansei period (1603–1868) The landslide presently functions as a geosite within the Happo ‐ Shirakami Geopark and plays a crucial role in environmental education initiatives Visitors to the Tomeyama landslide totaled 1668, 1329, and 1415 in 2019, 2020, and 2021, respectively [19] Figure 1. Maps and photograph of the Tomeyama study area, showing the location, topography,

Sustainability 2023 , 15 , 16572 3 of 14 and geology. ( a ) Location map (modified from the GSI Tile published by the Geospatial Information Authority of Japan). ( b ) NE-oriented photograph of the Tomeyama landslide. ( c ) Topography of the Tomeyama landslide (modified from the 1:25,000 scale topographic map published by the Geospatial Information Authority of Japan). The representation of the landslide scarp and displaced block is from [ 15 ]. ( d ) Geological map of the study area (from [ 16 ]). 2. Study Area The Tomeyama landslide is located on a gentle slope of the Shirakami mountains, where 13% of the area has been designated as a Natural World Heritage site. The landslide spans an elevation of approximately 150–250 m (Figure 1 c). Determining the timing and the driving factor behind the landslide occurrence is challenging due to the scarcity of historical records in and around the study area. The geology of the Tomeyama landslide comprises a lower layer of Late Miocene to Early Pliocene mudstone and an upper layer of andesite and its associated pyroclastic rock (Figure 1 d) [ 16 ]. The andesite volcanic event has a history eruptions dating back to 6.6 Ma [ 17 ]. Vegetation in the study area consists of a cool-temperate deciduous broad-leaved forest, composed mainly of Siebold’s beech ( Fagus crenata ) and Pterocarya rhoifolia The average annual rainfall in Happo town from 1991 to 2020 was 1501.6 mm; the largest monthly total rainfall occurred in July (172.2 mm) and the smallest in February (68.9 mm) [ 18 ]. The forest around the Tomeyama landslide has been protected from logging since the Hansei period (1603–1868). The landslide presently functions as a geosite within the Happo-Shirakami Geopark and plays a crucial role in environmental education initiatives. Visitors to the Tomeyama landslide totaled 1668, 1329, and 1415 in 2019, 2020, and 2021, respectively [ 19 ]. 3. Methods 3.1. Landslide Topography Landslide topography was interpreted utilizing a CS stereogram derived from a 2.5 m-mesh AW 3 D digital elevation model (DEM). The CS stereogram was generated using the CSMap- Maker plugin in QGIS [ 20 ]. This CS stereogram includes two sets of curvature and slope layers (Figure 2 ). During the generation of the CS stereogram, a color ramp and a 50% transparency were applied to these layers. Results of the CS stereogram were validated in the field Sustainability 2023 , 15 , x FOR PEER REVIEW 4 of 15 3. Methods 3.1. Landslide Topography Landslide topography was interpreted utilizing a CS stereogram derived from a 2.5 m ‐ mesh AW 3 D digital elevation model (DEM) The CS stereogram was generated using the CSMapMaker plugin in QGIS [20] This CS stereogram includes two sets of curvature and slope layers (Figure 2) During the generation of the CS stereogram, a color ramp and a 50% transparency were applied to these layers Results of the CS stereogram were validated in the field Figure 2. Example of the generation of a CS stereogram following the process described by [20] 3.2. Surveys of Plant Species Composition and Cover Plant species composition and cover were surveyed within square plots measuring 20 m on each side on the upper slope of the displaced landslide block (Plots 1, 2, and 4) and on the lower slope near the toe of the displaced block (Plot 3) of the landslide (Figures 3 and 4) Due to the steep slope at the toe of the landslide, making it unsuitable for the survey, Plot 3 was chosen on the lower slope near the toe of the displaced block It is worth noting that the vegetation in this area is visually similar to that found on the toe of the landslide In each plot, 16 sub ‐ plots were separated by 5 m intervals Field surveys were conducted on 19 and 26 July 2022 Slope angles are steeper on the lower slope near the toe of the landslide compared with the upper slope In the upper slope plots, the distribution of slope angles followed a normal distribution, with Plot 1 having a modal value of 20°–25°, whereas Plots 2 and 4 had a modal value of 10°–15 ° (Figure 5) The mean slope angles in Plots 1, 2, and 4 were 20.0 ° , 16.5 ° , and 12.1 ° , respectively In Plot 3, near the toe of the landslide, slope angle exhibited a normal distribution with a mode of 25 ° –30 ° and a mean slope angle of 25.2 ° All plant species within each sub ‐ plot of the four survey plots were identified and recorded in four layers of vertical structure (herb layer: 0–1.5 m, shrub layer: 1.5–5 m, understory layer: 5–8 m, and canopy layer: >8 m) The plant cover of each layer was estimated by visual assessment of the percentage of the sub ‐ plot covered by each plant species and recorded using a scale of six coverage classes [21]: class 5 (75–100%), class 4 (50–75%), class 3 (25–50%), class 2 (10–25%), class 1 (<10%), and class “+” (for very few individuals accounting for less than 1% of the area) [22] In cases where the same species appeared in multiple layers, the highest coverage class observed among the layers was assigned The classification of the surveyed vegetation into existing communities was determined based on phytosociology This determination involved referring to the characteristic and differential species of specific plant communities that have been reported in the vicinity of the survey area [23,24] Figure 2. Example of the generation of a CS stereogram following the process described by [ 20 ]. 3.2. Surveys of Plant Species Composition and Cover Plant species composition and cover were surveyed within square plots measuring 20 m on each side on the upper slope of the displaced landslide block (Plots 1, 2, and 4) and on the lower slope near the toe of the displaced block (Plot 3) of the landslide (Figures 3 and 4 ).

Sustainability 2023 , 15 , 16572 4 of 14 Due to the steep slope at the toe of the landslide, making it unsuitable for the survey, Plot 3 was chosen on the lower slope near the toe of the displaced block. It is worth noting that the vegetation in this area is visually similar to that found on the toe of the landslide. In each plot, 16 sub-plots were separated by 5 m intervals. Field surveys were conducted on 19 and 26 July 2022 Sustainability 2023 , 15 , x FOR PEER REVIEW 5 of 15 Figure 3. Surveyed plots of plant species composition and cover The red polyline indicates the walking route designated for visitors Figure 4. Photographs of survey plots showing plant species composition and cover ( a ) Plot 1; ( b ) Plot 2; ( c ) Plot 3; ( d ) Plot 4 Plot locations are shown in Figure 3 Figure 3. Surveyed plots of plant species composition and cover. The red polyline indicates the walking route designated for visitors Sustainability 2023 , 15 , x FOR PEER REVIEW 5 of 15 Figure 3. Surveyed plots of plant species composition and cover The red polyline indicates the walking route designated for visitors Figure 4. Photographs of survey plots showing plant species composition and cover ( a ) Plot 1; ( b ) Plot 2; ( c ) Plot 3; ( d ) Plot 4 Plot locations are shown in Figure 3 Figure 4. Photographs of survey plots showing plant species composition and cover. ( a ) Plot 1; ( b ) Plot 2; ( c ) Plot 3; ( d ) Plot 4. Plot locations are shown in Figure 3 . Slope angles are steeper on the lower slope near the toe of the landslide compared with the upper slope. In the upper slope plots, the distribution of slope angles followed a normal distribution, with Plot 1 having a modal value of 20 ◦ –25 ◦ , whereas Plots 2 and 4 had a

Sustainability 2023 , 15 , 16572 5 of 14 modal value of 10 ◦ –15 ◦ (Figure 5 ). The mean slope angles in Plots 1, 2, and 4 were 20.0 ◦ , 16.5 ◦ , and 12.1 ◦ , respectively. In Plot 3, near the toe of the landslide, slope angle exhibited a normal distribution with a mode of 25 ◦ –30 ◦ and a mean slope angle of 25.2 ◦ Sustainability 2023 , 15 , x FOR PEER REVIEW 6 of 15 Figure 5. Percentage frequency distributions of slope gradient in survey plots of plant species composition and cover 4. Results and Discussion 4.1. Landslide Topography The Tomeyama landslide is approximately 350 m wide and 450 m long and has an area of about 0.1 km 2 (Figure 6) The landslide occurred below an elevation of approximately 250 m, and the displaced block extends in front of a main scarp with a height of 40 m The main scarp constitutes a horseshoe ‐ shaped cliff facing predominantly northwest The slope of the landslide generally faces northwest, with the distal end facing the river The displaced block of the landslide exhibits gentle hilly terrain, with the mid ‐ slope area having a slope angle of approximately 5°–15° Small valleys are distributed within the displaced block and formed after the occurrence of the landslide The distal end of the displaced block has convex steep slopes with slope angles exceeding 30° On the main scarp, two smaller horseshoe ‐ shaped scarps can be observed (Figure 6 a) Below each of these two smaller secondary scarps, small ‐ scale displaced bodies corresponding to each scarp are observed, suggesting the occurrence of secondary landslides associated with the enlargement of the pre ‐ existing main landslide scarp In addition, the displaced bodies of the secondary landslides have been pushed and accumulated into the back part of the main displaced block, creating concave areas with a maximum width of approximately 50–60 m (Figure 6) The landslide has been mapped previously from aerial photographs [15], which revealed a main landslide scarp and its related displaced block (Figure 1 c) Our topographic investigation confirms the main scarp but additionally identifies the horseshoe ‐ shaped smaller scarps, displaced bodies, and concave areas formed by secondary landslides The topography resulting from the secondary landslide was also observed during the field study Figure 5. Percentage frequency distributions of slope gradient in survey plots of plant species composition and cover All plant species within each sub-plot of the four survey plots were identified and recorded in four layers of vertical structure (herb layer: 0–1.5 m, shrub layer: 1.5–5 m, understory layer: 5–8 m, and canopy layer: >8 m). The plant cover of each layer was estimated by visual assessment of the percentage of the sub-plot covered by each plant species and recorded using a scale of six coverage classes [ 21 ]: class 5 (75–100%), class 4 (50–75%), class 3 (25–50%), class 2 (10–25%), class 1 (<10%), and class “+” (for very few individuals accounting for less than 1% of the area) [ 22 ]. In cases where the same species appeared in multiple layers, the highest coverage class observed among the layers was assigned The classification of the surveyed vegetation into existing communities was determined based on phytosociology. This determination involved referring to the characteristic and differential species of specific plant communities that have been reported in the vicinity of the survey area [ 23 , 24 ]. 4. Results and Discussion 4.1. Landslide Topography The Tomeyama landslide is approximately 350 m wide and 450 m long and has an area of about 0.1 km 2 (Figure 6 ). The landslide occurred below an elevation of approximately 250 m, and the displaced block extends in front of a main scarp with a height of 40 m. The main scarp constitutes a horseshoe-shaped cliff facing predominantly northwest. The slope of the landslide generally faces northwest, with the distal end facing the river. The displaced block of the landslide exhibits gentle hilly terrain, with the mid-slope area having a slope angle of approximately 5 ◦ –15 ◦ . Small valleys are distributed within the displaced block and formed after the occurrence of the landslide. The distal end of the displaced block has convex steep slopes with slope angles exceeding 30 ◦ On the main scarp, two smaller horseshoe-shaped scarps can be observed (Figure 6 a). Below each of these two smaller secondary scarps, small-scale displaced bodies corresponding to each scarp are observed, suggesting the occurrence of secondary landslides associated with the enlargement of the pre-existing main landslide scarp. In addition, the displaced bodies of the secondary landslides have been pushed and accumulated into the back part of the main displaced block, creating concave areas with a maximum width of approximately 50– 60 m (Figure 6 ). The landslide has been mapped previously from aerial photographs [ 15 ], which revealed a main landslide scarp and its related displaced block (Figure 1 c). Our topographic investigation confirms the main scarp but additionally identifies the horseshoe-

Sustainability 2023 , 15 , 16572 6 of 14 shaped smaller scarps, displaced bodies, and concave areas formed by secondary landslides The topography resulting from the secondary landslide was also observed during the field study Sustainability 2023 , 15 , x FOR PEER REVIEW 7 of 15 Figure 6. Topography and topographic cross ‐ section of the Tomeyama landslide ( a ) Landslide topography interpreted using a CS stereogram; ( b ) topographic cross ‐ section of the landslide (X ‐ Y, location shown in ( a ) The cross ‐ section is from the AW 3 D DEM 4.2. Plant Species Composition and Cover Surveys The numbers of species and plants observed in each layer of vertical structure are shown for Plots 1 to 4 in Figure 7 Only the number of species was recorded for the herb layer, on account of the difficulty in determining the exact number of plants for this layer The results indicate that, regardless of the survey plot, the number of species was highest in the herb layer, followed by the shrub layer In addition, the number of plants was highest in the shrub layer, followed by the canopy and understory layers Figure 8 presents the results for tree height and circumstance at breast height in the canopy layer for Plots 1 to 4 The mean height of trees in each plot ranged from 16.4 to 17.5 m, with the tallest tree being Fagus crenata , reaching 30 m in Plot 2 The mean circumstance ranged from 1.6 m for Plots 1 to 3 to 1.8 m for Plot 4 Figure 6. Topography and topographic cross-section of the Tomeyama landslide. ( a ) Landslide topography interpreted using a CS stereogram; ( b ) topographic cross-section of the landslide (X-Y, location shown in ( a ). The cross-section is from the AW 3 D DEM 4.2. Plant Species Composition and Cover Surveys The numbers of species and plants observed in each layer of vertical structure are shown for Plots 1 to 4 in Figure 7 . Only the number of species was recorded for the herb layer, on account of the difficulty in determining the exact number of plants for this layer. The results indicate that, regardless of the survey plot, the number of species was highest in the herb layer, followed by the shrub layer. In addition, the number of plants was highest in the shrub layer, followed by the canopy and understory layers. Figure 8 presents the results for tree height and circumstance at breast height in the canopy layer for Plots 1 to 4. The mean height of trees in each plot ranged from 16.4 to 17.5 m, with the tallest tree being Fagus crenata , reaching 30 m in Plot 2. The mean circumstance ranged from 1.6 m for Plots 1 to 3 to 1.8 m for Plot 4 Tables 1 – 4 provide summaries of the plant species composition and coverage classes for the upper slope of the displaced block (Plots 1, 2, and 4) and the lower slope near the toe of the displaced block (Plot 3) of the Tomeyama landslide. In Plots 1, 2, and 4 on the gentle upper slope, totals of 39, 56, and 45 plant species were observed, respectively. Of these, 14 to 16 species were identified as character and differential species of Japanese beech forest, accounting for nearly half of the species in the herb layer.

Sustainability 2023 , 15 , 16572 7 of 14 Moreover, character species strongly associated with this forest community, such as Lindera umbellata var membranacea Moriyama , Aucuba japonica var borealis Miyabe et Kudo , Disporum smilacinum , and Hamamelis japonica var obtusata Matsumura were present with a higher coverage class. In contrast, only 2–5 species were identified as character and differential species of Pterocarya rhoifolia forest Sustainability 2023 , 15 , x FOR PEER REVIEW 8 of 15 Figure 7. Number of identified species (all layers) and plant counts (excluding the herb layer) stratified by vegetation survey for ( a – d ) Plots 1 to 4 Figure 8. Survey results for the canopy layer in vegetation survey Plots 1 to 4 ( a ) Tree height; ( b ) tree diameter at breast height Tables 1–4 provide summaries of the plant species composition and coverage classes for the upper slope of the displaced block (Plots 1, 2, and 4) and the lower slope near the toe of the displaced block (Plot 3) of the Tomeyama landslide In Plots 1, 2, and 4 on the gentle upper slope, totals of 39, 56, and 45 plant species were observed, respectively Of these, 14 to 16 species were identified as character and differential species of Japanese beech forest, accounting for nearly half of the species in the herb layer Moreover, character species strongly associated with this forest community, such as Lindera umbellata var membranacea Moriyama , Aucuba japonica var borealis Miyabe et Kudo , Disporum smilacinum , and Hamamelis japonica var obtusata Matsumura were present with a higher coverage class In contrast, only 2–5 species were identified as character and differential species of Pterocarya rhoifolia forest On the lower slope near the toe of the landslide (Plot 3), a total of 70 plant species were identified Of these, 14 species were recognized as character and differential species of Japanese beech forest The percentages of plant cover of the identified character species of this forest community, including Lindera umbellata var membranacea Moriyama , Aucuba japonica var borealis Miyabe et Kudo , and Disporum smilacinum , were low, with the Aucuba japonica var borealis Miyabe et Kudo falling in class 2, Lindera umbellata var membranacea Figure 7. Number of identified species (all layers) and plant counts (excluding the herb layer) stratified by vegetation survey for ( a – d ) Plots 1 to 4 Sustainability 2023 , 15 , x FOR PEER REVIEW 8 of 15 Figure 7. Number of identified species (all layers) and plant counts (excluding the herb layer) stratified by vegetation survey for ( a – d ) Plots 1 to 4 Figure 8. Survey results for the canopy layer in vegetation survey Plots 1 to 4 ( a ) Tree height; ( b ) tree diameter at breast height Tables 1–4 provide summaries of the plant species composition and coverage classes for the upper slope of the displaced block (Plots 1, 2, and 4) and the lower slope near the toe of the displaced block (Plot 3) of the Tomeyama landslide In Plots 1, 2, and 4 on the gentle upper slope, totals of 39, 56, and 45 plant species were observed, respectively Of these, 14 to 16 species were identified as character and differential species of Japanese beech forest, accounting for nearly half of the species in the herb layer Moreover, character species strongly associated with this forest community, such as Lindera umbellata var membranacea Moriyama , Aucuba japonica var borealis Miyabe et Kudo , Disporum smilacinum , and Hamamelis japonica var obtusata Matsumura were present with a higher coverage class In contrast, only 2–5 species were identified as character and differential species of Pterocarya rhoifolia forest On the lower slope near the toe of the landslide (Plot 3), a total of 70 plant species were identified Of these, 14 species were recognized as character and differential species of Japanese beech forest The percentages of plant cover of the identified character species of this forest community, including Lindera umbellata var membranacea Moriyama , Aucuba japonica var borealis Miyabe et Kudo , and Disporum smilacinum , were low, with the Aucuba japonica var borealis Miyabe et Kudo falling in class 2, Lindera umbellata var membranacea Figure 8. Survey results for the canopy layer in vegetation survey Plots 1 to 4. ( a ) Tree height; ( b ) tree diameter at breast height Table 1. Summary of plant species and their coverage classes in Plot 1 Plant Species Cover Plant Species Cover Lindera umbellata var. membranacea Moriyama 1,4 5 Pyrola japonica 3 + Sasa senanensis (Fr. Et Sav.) Rehder 3 5 Ilex crenata Thunb 3 + Aucuba japonica var. borealis Miyabe et Kudo 1,4 5 Acer rufinerve 3 + Acer japonicum Thunb 1 4 Daphniphyllum macropodum var humile Rosenthal 1 + Acanthopanax sciadophylloides Franch. Et Savat 1 4 Menziesia multiflora Maxim Var longicalyx 3 + Acer palmatum var matsumurae Makino 3 3 Symplocos chinensis var leucocarpa f. pilosa Ohwi 3 + Fagus crenata Blume 1 2 Blechnum niponicum 1 +

Sustainability 2023 , 15 , 16572 8 of 14 Table 1. Cont Plant Species Cover Plant Species Cover Viburnum furcatum Blume 1 2 Disporum smilacinum 1,4 + Sasa senanensis var senanensis 3 2 Hydrangea petiolaris Sieb. Et Zucc 3 + Euonymus oxyphyllus Miq Var oxyphy 3 2 Mitchella undulata 3 + Schizophragma hydrangeoides Sieb. Et Zucc 1 1 Huperzia serrata 3 + Prunus grayana Linn 3 1 Mognolia obovate Thunb 1 + Carex sp 3 1 Hamamelis japonica var. obtusata Matsumura 1,4 + Rhus ambigua Lavallee 1 1 Parasenecio delphiniifolius var. delphiniifolius 2,4 + Cephalotaxus harringtonia var nana Rehd 1 1 Rhus trichocarpa Miq 3 + Ardisia japonica Blume 3 1 Styras obassia Sieb. Et Zucc 3 + Sorbus alnifolia C. Koch 3 1 Styrax japonica Sieb. Et Zucc 3 + Fraxinus lanuginosa Koidz 3 + Wisteria floribunda DC 3 + Acer mono Maxim 2 + Callicarpa japonica Thunb 3 + Maianthemum japonicum 3 + 1 Species related to the Japanese beech forest [ 23 , 24 ]. 2 Species related to the Pterocarya rhoifolia forest [ 23 , 24 ]. 3 Neither of the above [ 23 , 24 ]. 4 Bold: indicator species [ 24 ]. Table 2. Summary of plant species and their coverage classes in Plot 2 Plant Species Cover Plant Species Cover Lindera umbellata var. membranacea Moriyama 1,4 4 Galium odoratum 3 + Sasa senanensis (Fr. Et Sav.) Rehder 3 4 Lilium medeoloides var medeoloides 3 + Viburnum furcatum Blume 1 4 Actinidia argute Planch 3 + Viburnum dilatatum Thunb 3 3 Acanthopanax sciadophylloides Franch. Et Savat 1 + Aucuba japonica var. borealis Miyabe et Kudo 1,4 3 Smilax china Linn 3 + Maianthemum dilatatum 3 3 Blechnum niponicum 1 + Acer japonicum Thunb 1 3 Euonymus oxyphyllus Miq Var oxyphy 3 + Fagus crenata Blume 1 2 Mitchella undulata 3 + Schizophragma hydrangeoides Sieb. Et Zucc 1 2 Skimmia japonica var intermedia f. repens Hara 1 + Menziesia multiflora Maxim Var longicalyx 3 2 Tripterospermum japonicum var japonicum 3 + Carex sp 3 2 Panax japonicus var japonicus 2 + Hydrangea petiolaris Sieb. Et Zucc 3 2 Viola rostrata 3 + Tripetaleia paniculata Sieb. Et Zucc 3 2 Sorbus commixta Hedl 1 + Acer rufinerve 3 1 Hydrangea paniculata Sieb 3 + Prunus grayana Linn 3 1 Cephalotaxus harringtonia var nana Rehd 1 + Daphniphyllum macropodum var humile Rosenthal 1 1 Phryma leptostachya subsp. Asiatica var asiatica 3 + Calanthe discolor var discolor 3 1 Leucothoe grayana Maxim 3 + Disporum smilacinum 1,4 1 Ilex leucoclada Makino 1 + Rhus ambigua Lavallee 1 1 Wisteria floribunda DC 3 + Ilex crenata var paludosa Hara 3 1 Solidago virgaurea subsp. Leiocarpa var leiocarpa 3 + Callicarpa japonica Thunb 3 1 Polygonatum lasianthum Maxim 3 + Rhus trichocarpa Miq 3 1 Parasenecio delphiniifolius var. delphiniifolius 2,4 + Solidago virgaurea subsp. Asiatica var asiatica 3 + Athyrium vidalii 3 + Fraxinus lanuginosa Koidz 3 + Rhododendron kaempferi Planch 3 + Acer mono Maxim 2 + Acer palmatum var matsumurae Makino 3 + Abelia spathulata var stenophylla 1 + Prunus sargentii Rehder 3 + Quercus crispula Blume 1 + Styras obassia Sieb. Et Zucc 3 + Menziesia multiflora Maxim 3 + Clethra barbinervis Sieb. Et Zucc 3 + 1 Species related to the Japanese beech forest [ 23 , 24 ]. 2 Species related to the Pterocarya rhoifolia forest [ 23 , 24 ]. 3 Neither of the above [ 23 , 24 ]. 4 Bold: indicator species [ 24 ]. Table 3. Summary of plant species and their coverage classes in Plot 3 Plant Species Cover Plant Species Cover Sasa senanensis (Fr. Et Sav.) Rehder 3 4 Acanthopanax sciadophylloides Franch. Et Savat 1 + Carex sp 3 4 Euonymus alatus var alatus f. striatus 3 + Hydrangea petiolaris Sieb. Et Zucc 3 4 Polystichum retrosopaleaceum 2 +

Sustainability 2023 , 15 , 16572 9 of 14 Table 3. Cont Plant Species Cover Plant Species Cover Acer japonicum Thunb 1 4 Prunus ssiori Fr. Schm 3 + Viburnum furcatum Blume 1 3 Blechnum niponicum 1 + Aesculus turbinata Blume 2 3 Viola vaginata 2,4 + Rubus buergeri 3 3 Osmunda japonica + Dryopteris sabaei 1 3 Smilax nipponica + Dryopteris crassirhizoma 2 2 Disporum smilacinum 1,4 + Athyrium clivicola 3 2 Paris tetraphylla var tetraphylla 1 + Rubus crataegifolius 3 2 Rhus ambigua Lavallee 1 + Aucuba japonica var. borealis Miyabe et Kudo 1,4 2 Viola verecunda var verecunda 3 + Arachniodes borealis 3 2 Huperzia serrata 3 + Diplazium sibiricum var glabrum 3 2 Ulmus pumila Linn 3 + Lindera umbellata var. membranacea Moriyama 1,4 1 Adenocaulon himalaicum 3 + Viburnum dilatatum Thunb 3 1 Hydrangea paniculata Sieb 3 + Polystichum tripteron 2 1 Styras obassia Sieb. Et Zucc 3 + Sambucus chinensis var chinensis 3 1 Chloranthus quadrifolius 3 + Panax japonicus var japonicus 2 1 Ilex leucoclada Makino 1 + Cephalotaxus harringtonia var nana Rehd 1 1 Wisteria floribunda DC 3 + Oxalis griffithii var griffithii 3 1 Fagus crenata Blume 1 + Solidago virgaurea subsp. Asiatica var asiatica 3 + Athyrium yokoscense var yokoscense 3 + Sorbus alnifolia C. Koch 3 + Disporum sessile var sessile 3 + Acer mono Maxim 2 + Maianthemum dilatatum 3 + Asarum sieboldii 3 + Cornus controversa Hemsley 2 + Acer rufinerve 3 + Quercus crispula Blume 1 + Elatostema japonicum var. majus 2,4 + Persicaria thunbergii var thunbergii 3 + Hydrangea serrata var megacarpa H. Ohba 2 + Polygonatum lasianthum Maxim 3 + Trillium apetalon 3 + Dryopteris monticola 2,4 + Platanthera sachalinensis 3 + Ardisia japonica Blume 3 + Prunus sargentii Rehder 3 + Athyrium vidalii 3 + Polystichum microchlamys var microchlamys 3 + Acer palmatum var matsumurae Makino 3 + Coptis japonica var anemonifolia 3 + Prunus grayana Linn 3 + Clerodendrum trichotomum Thunb 3 + Elliottia paniculata (Siebold et Zucc.) Hook.f 3 + Onoclea sensibilis var interrupta 3 + Clethra barbinervis Sieb. Et Zucc 3 + 1 Species related to the Japanese beech forest [ 23 , 24 ]. 2 Species related to the Pterocarya rhoifolia forest [ 23 , 24 ]. 3 Neither of the above [ 23 , 24 ]. 4 Bold: indicator species [ 24 ]. Table 4. Summary of plant species and their coverage classes in Plot 4 Plant Species Cover Plant Species Cover Sasa senanensis (Fr. Et Sav.) Rehder 3 5 Daphniphyllum macropodum var humile Rosenthal 1 + Aucuba japonica var. borealis Miyabe et Kudo 1,4 4 Calanthe sp 3 + Fagus crenata Blume 1 4 Betula maximowicziana Rege 3 + Viburnum furcatum Blume 1 3 Viburnum dilatatum Thunb 3 + Carex sp 3 2 Carpinus cordata var cordata 3 + Skimmia japonica var intermedia f. repens Hara 1 2 Blechnum niponicum 1 + Stegnogramma pozoi subsp. Mollissima 3 2 Viola vaginata 2,4 + Schizophragma hydrangeoides Sieb. Et Zucc 1 1 Smilax nipponica 3 + Prunus grayana Linn 3 1 Elliottia paniculata (Siebold et Zucc.) Hook.f 3 + Lindera umbellata var. membranacea Moriyama 1,4 1 Euonymus oxyphyllus Miq Var oxyphy 3 + Disporum smilacinum 1,4 1 Aesculus turbinata Blume 2 + Rhus ambigua Lavallee 1 1 Panax japonicus var japonicus 2 + Hydrangea petiolaris Sieb. Et Zucc 3 1 Astilbe odontophylla var odontophylla 3 + Cephalotaxus harringtonia var nana Rehd 1 1 Calanthe reflexa 3 + Maianthemum japonicum 3 1 Hydrangea paniculata Sieb 3 + Fraxinus lanuginosa Koidz 3 + Ilex crenata var paludosa Hara 3 + Meliosma myriantha 3 + Wisteria floribunda DC 3 +

Sustainability 2023 , 15 , 16572 10 of 14 Table 4. Cont Plant Species Cover Plant Species Cover Acer mono Maxim 2 + Maianthemum dilatatum 3 + Abelia spathulata var stenophylla 1 + Dryopteris sabaei 1 + Asarum sieboldii 3 + Acanthopanax sciadophylloides Franch. Et Savat 1 + Quercus crispula Blume 1 + Acer japonicum Thunb 1 + Hydrangea serrata var megacarpa H. Ohba 3 + Parasenecio delphiniifolius var. delphiniifolius 2,4 + Rhododendron kaempferi Planch 3 + 1 Species related to the Japanese beech forest [ 23 , 24 ]. 2 Species related to the Pterocarya rhoifolia forest [ 23 , 24 ]. 3 Neither of the above [ 23 , 24 ]. 4 Bold: indicator species [ 24 ]. On the lower slope near the toe of the landslide (Plot 3), a total of 70 plant species were identified. Of these, 14 species were recognized as character and differential species of Japanese beech forest. The percentages of plant cover of the identified character species of this forest community, including Lindera umbellata var membranacea Moriyama , Aucuba japonica var borealis Miyabe et Kudo , and Disporum smilacinum , were low, with the Aucuba japonica var borealis Miyabe et Kudo falling in class 2, Lindera umbellata var membranacea Moriyama in class 1, and Disporum smilacinum in class “+” in the coverage class system used in this study. In contrast, 11 species were identified as character and differential species of Pterocarya rhoifolia forest. The percentages of plant cover of the identified character species of this forest community, including Elatostema japonicum var majus , Viola vaginata , and Dryopteris monticola , were low, falling in class “+” On the basis of the presented results, it is concluded that the vegetation observed in the survey plots on the gentle upper slope belongs to the Japanese beech forest (Figure 9 ). Determining the community to which the vegetation on the lower slope near the toe of the landslide belongs is challenging, although a greater number of species related to the Pterocarya rhoifolia forest were found in the plot on the lower slope compared with the plots on the upper slope. Plant community composition differences were observed between the upper and lower slopes of the landslide. Previous studies have explored the relationship between plant community composition and the geomorphic environment of the Shirakami mountains. Mishima et al. [ 4 ] conducted surveys within a landslide area located on the eastern side of the Shirakami mountains, including evaluations of vegetation, subsoil structure, and soil erosion levels. They recorded the presence of Japanese beech forest on the arid upper slope of the landslide, where the soil layer is minimal. In contrast, Pterocarya rhoifolia forest displayed a preference for the moister conditions on the lower slope. Comparable observations have been reported by Tsou et al. [ 25 ] for a landslide area on the western side of the Shirakami mountains. Our results reveal similarities with previous studies. It is worth noting that the Japanese beech forest represents the climatic climax forest of the northern Japan Sea region, whereas the Pterocarya rhoifolia forest is the most widely distributed community within the topographic climax forest of the Shirakami mountains [ 26 ]. In this study, we investigated the relationship between the present composition of plant communities and topography of the Tomeyama landslide. However, it is essential to acknowledge that plant species composition is also influenced by environmental variables such as aspect, soil porosity, and saturation moisture content, among others [ 27 ], which could be the focus of future studies. In addition, the present plant composition and distribution of plant communities could also be influenced by the timescale of post-landslide geomorphic evolution, the process of vegetation succession, and the pace of these transitions [ 1 , 28 , 29 ]. The present plant composition and distribution of plant communities is likely an outcome of the interplay between these dynamic temporal aspects, which should be investigated in a future study.

Sustainability 2023 , 15 , 16572 11 of 14 Sustainability 2023 , 15 , x FOR PEER REVIEW 11 of 15 Carex sp 3 2 Carpinus cordata var cordata 3 + Skimmia japonica var intermedia f. repens Hara 1 2 Blechnum niponicum 1 + Stegnogramma pozoi subsp. Mollissima 3 2 Viola vaginata 2,4 + Schizophragma hydrangeoides Sieb. Et Zucc. 1 1 Smilax nipponica 3 + Prunus grayana Linn. 3 1 Elliottia paniculata (Siebold et Zucc.) Hook.f. 3 + Lindera umbellata var. membranacea Moriyama 1,4 1 Euonymus oxyphyllus Miq. Var oxyphy 3 + Disporum smilacinum 1,4 1 Aesculus turbinata Blume 2 + Rhus ambigua Lavallee 1 1 Panax japonicus var japonicus 2 + Hydrangea petiolaris Sieb. Et Zucc. 3 1 Astilbe odontophylla var odontophylla 3 + Cephalotaxus harringtonia var nana Rehd. 1 1 Calanthe reflexa 3 + Maianthemum japonicum 3 1 Hydrangea paniculata Sieb. 3 + Fraxinus lanuginosa Koidz. 3 + Ilex crenata var paludosa Hara 3 + Meliosma myriantha 3 + Wisteria floribunda DC. 3 + Acer mono Maxim. 2 + Maianthemum dilatatum 3 + Abelia spathulata var stenophylla 1 + Dryopteris sabaei 1 + Asarum sieboldii 3 + Acanthopanax sciadophylloides Franch. Et Savat. 1 + Quercus crispula Blume 1 + Acer japonicum Thunb. 1 + Hydrangea serrata var megacarpa H. Ohba 3 + Parasenecio delphiniifolius var. delphiniifolius 2,4 + Rhododendron kaempferi Planch. 3 + 1 Species related to the Japanese beech forest [23,24] 2 Species related to the Pterocarya rhoifolia forest [23,24] 3 Neither of the above [23,24] 4 Bold: indicator species [24] On the basis of the presented results, it is concluded that the vegetation observed in the survey plots on the gentle upper slope belongs to the Japanese beech forest (Figure 9) Determining the community to which the vegetation on the lower slope near the toe of the landslide belongs is challenging, although a greater number of species related to the Pterocarya rhoifolia forest were found in the plot on the lower slope compared with the plots on the upper slope Plant community composition differences were observed between the upper and lower slopes of the landslide Figure 9. Schematic diagram illustrating differences in plant community composition related to the topography between the upper and lower slopes of the displaced landslide block The legend shows plant species that closely related to the plant community composition and high coverage class of plant cover Figure 9. Schematic diagram illustrating differences in plant community composition related to the topography between the upper and lower slopes of the displaced landslide block. The legend shows plant species that closely related to the plant community composition and high coverage class of plant cover 4.3. Enhancing Enviromental Education and Sustainable Management With the aim of enhancing environmental education and sustainable management, we generated a trifold brochure (Figures 10 and 11 ) to offer the general public insights into the natural environment of the Tomeyama landslide. This content is centered on the relationship between plant species composition and topography of the landslide area. Figure 10 presents the front side of the brochure, which provides general details about the Tomeyama landslide. Figure 11 presents the back side of the brochure, which summarizes the information from Sections 4.1 and 4.2 of this paper. Guides who introduce visitors to the Tomeyama area are expected to utilize the brochure, making it also valuable for environmental education in schools and local communities. As noted by Koizumi and Chakraborty [ 30 ], incorporating environmental education regarding the local geoecological system is crucial for sustainable management, which should be based on knowledge of the natural environment. As a result, the findings of our study make a significant contribution to environmental education and sustainable management.

Sustainability 2023 , 15 , 16572 12 of 14 Sustainability 2023 , 15 , x FOR PEER REVIEW 13 of 15 Figure 10. Proposed trifold brochure (front side) Figure 11. Proposed trifold brochure (back side) Figure 10. Proposed trifold brochure (front side) Sustainability 2023 , 15 , x FOR PEER REVIEW 13 of 15 Figure 10. Proposed trifold brochure (front side) Figure 11. Proposed trifold brochure (back side) Figure 11. Proposed trifold brochure (back side).

Sustainability 2023 , 15 , 16572 13 of 14 5. Conclusions This study focused on enhancing environmental education and sustainable management by measuring the relationship between the plant species composition and the topography of the Tomeyama landslide in the Happo-Shirakami Geopark, Japan. Topographic analysis shows that the landslide occupies a relatively compact space of approximately 0.1 km 2 . This landslide originated from a large-scale primary movement and subsequently underwent reactivation, particularly along its main scarp, producing secondary scarps and displaced bodies. Our study included thorough surveys of plant species composition and cover across four plots, each measuring 20 m × 20 m: three on the upper slope and one on the convex lower foot slope. Results revealed rich plant diversity. On the upper slope, 40–55 plant species were identified, with 14–16 species related to the Japanese beech forest but only 2–5 species related to the Pterocarya rhoifolia forest. The lower slope plot contained 70 species, including 14 from the Japanese beech forest and 11 from the Pterocarya rhoifolia forest. Although categorizing the plant community of the lower slope proved challenging, there was a higher representation of Pterocarya rhoifolia forest species compared with the upper slope. These results indicate that specific plant species have adapted to the varying topography induced by the landslide. We have generated a trifold brochure to enhance environmental education and sustainable management by disseminating the information obtained in this study. This brochure will be used by Happo-Shirakami Geopark guides and for environmental education in schools and local communities Author Contributions: Conceptualization: C.-Y.T., H.Y. and M.-F.T.; data curation: C.-Y.T., H.Y., R.K and T.M.; methodology: C.-Y.T., H.Y. and M.-F.T.; analysis: C.-Y.T., H.Y., R.K. and M.-F.T.; supervision: C.-Y.T. and T.M.; writing—original draft: C.-Y.T., H.Y. and T.M.; writing—review and editing: C.-Y.T All authors have read and agreed to the published version of the manuscript Funding: This research was funded by a research grant from the Geoparks of Akita Prefecture in 2022 Institutional Review Board Statement: Not applicable Informed Consent Statement: Not applicable Data Availability Statement: Data are available upon request Acknowledgments: Akira Takahashi, Aya Ogasawara, and Masako Nejo provided valuable assistance during the field surveys. Insightful discussions with Shintaro Hayashi of Akita University, the Happo-cho Shirakami Guiding Association, and the Happo-cho Shirakami Geopark Guiding Association contributed greatly to this study Conflicts of Interest: The authors declare no conflict of interest References 1 Walker, L.R.; Shiels, A.B.; Bellingham, P.J.; Sparrow, A.D.; Fetcher, N.; Landau, F.H.; Lodge, D.J. Changes in abiotic influences on seed plants and ferns during 18 years of primary succession on Puerto Rican landslides J. Ecol 2013 , 101 , 650–661. [ CrossRef ] 2 Takaoka, S. Effects of landslides on vegetation with special reference to significance of studies from a geohistorical viewpoint Veg. Sci 2013 , 30 , 133–144, (In Japanese with English Abstract). [ CrossRef ] 3 Guariguata, M.R. Landslide disturbance and forest regeneration in the Upper Luquillo Mountains of Puerto Rico J. Ecol 1990 , 78 , 814–832. [ CrossRef ] 4 Mishima, Y.; Higaki, D.; Makita, H. Relationship between microtopography and plants in a small landslide area in the Shirakami Mountains Q. J. Geogr 2009 , 61 , 109–118, (In Japanese with English Abstract). [ CrossRef ] 5 Sakai, A.; Ohsawa, M. Vegetation pattern and microtopography on a landslide scar of Mt Kiyosumi, central Japan Ecol. Res 1993 , 8 , 47–56. [ CrossRef ] 6 Seiwa, K.; Miwa, Y.; Akasaka, S.; Kanno, H.; Tomita, M.; Saitoh, T.; Ueno, N.; Kimura, M.; Hasegawa, Y.; Konno, M.; et al. Landslide-facilitated species diversity in a beech-dominant forest Ecol. Res 2013 , 28 , 29–41. [ CrossRef ] 7 Morino, C.; Coratza, P.; Soldati, M. Landslides, a key landform in the global geological heritage Front. Earth Sci 2022 , 10 , 864760 [ CrossRef ] 8 Galadini, F. Ruins and remains as a background: Natural catastrophes, abandonment of medieval villages, and the perspective of civilization during the 20 th century in the central Apennines (Abruzzi Region, Central Italy) Sustainability 2022 , 14 , 9517 [ CrossRef ]

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