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農学部 農学部門森林環境持続性科学領域 |
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職名 |
准教授 |
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外部リンク |
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関連SDGs |
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論文 【 表示 ／ 非表示 】
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Yuji Tokumoto, Souta Okuyama, Koki Sueyoshi, Harunobu Tanigawa, Rui Ren, Wakana A. Azuma
Landscape and Ecological Engineering 2026年1月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Springer Nature
The increasing prevalence of abandoned secondary forests, resulting from human land use and forest management, often cause the dominance of specific plant species. In the Rokko mountain range (Hyogo Prefecture, Japan), Pieris japonica and dwarf bamboo form a dense understory, hindering the establishment of other plant species. This study investigated how diverse tree compositions and the selective removal of dominant understory plants affect soil environmental conditions (litter and humus contents and soil nutrient levels) as well as fungal community dynamics in these forests. Plots dominated by trees associated with ericoid mycorrhizal (ErM), arbuscular mycorrhizal (AM), and both ectomycorrhizal (ECM) and AM (ECM−AM) fungi had higher proportions of corresponding mycorrhizal fungi. Pieris removal led to enhanced humus accumulation and organic matter content and a shift toward pathotroph−symbiotic fungal dominance. Conversely, dwarf bamboo removal resulted in a minor increase in soil pH and a shift toward pathotrophic fungal communities. The effects of Pieris removal were also observed in plots following removal of both species. Understory management significantly alters soil biogeochemistry and fungal community composition and function. This study underscores the importance of maintaining tree diversity and implementing appropriate understory management strategies to conserve local fungal communities and landscape elements in secondary forests.
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Yuji Tokumoto, Ayumi Katayama
Ecological Research 41 ( 1 ) e70031 2026年1月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Wiley
The prevalence of unpalatable plants to deer increases in forests after browsing. Such a shrub, Pieris japonica (Ericaceae), has become the dominant understory vegetation in the Kyushu Mountain region of southern Japan. This monodominance has led to a shaded understory and a build-up of humus layers, with a remarkable scarcity of plantlets beneath the P. japonica populations. To investigate the mechanisms by which P. japonica dominance suppresses plant establishment, we quantified the plant numbers and survival in an area dominated by this species and conducted germination tests to identify the factors hindering understory germination and initial growth. We observed a limited number of plantlets and recruitment in areas dominated by Pieris populations compared to the adjacent areas, while survival rates remained consistent across sites. Germination tests using humus collected from under the Pieris populations revealed a significantly reduced radicle length compared to the controls. This finding suggests that the modified organic horizon caused by the dominance of Pieris is a major factor inhibiting root growth and, ultimately, limiting plant establishment. These results offer insights for managing Pieris populations.
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徳本 雄史, 雉子谷 佳男
Journal of Forest Research 1 - 8 2025年5月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Taylor & Francis
Castanopsis sieboldii is a dominant tree species in the warm-temperate forests of western Japan, playing crucial roles in forest ecosystems and human cultures. This species and Castanopsis cuspidata often hybridize in overlapping distribution regions, leading to long-standing debates over their classifications. Although several morphological and genetic markers have been proposed to differentiate the species and their hybrids, the genes underlying phenotypic differences remain unknown. In this study, we estimated the genome size and assembled the genome of Castanopsis sieboldii subsp. sieboldii. Using short reads (98.68 Gb generated using DNBSEQ-G400 and DNBSEQ-T7 sequencers), the genome size was estimated at 812.91 Mbp, with a heterozygosity level of 2.13%. Genome assembly was conducted using long reads generated via MinION (20.54 Gb; 25.30× genome coverage) and Revio (21.59 Gb; 26.59× genome coverage). The assembled genome consisted of 267 contigs with a total length of 959.00 Mb and an N50 length of 22.26 Mb. The draft genome achieved over 90% read mapping rates for both DNA and RNA sequencing reads as well as 98.7% gene completeness, as estimated using the Benchmarking Universal Single-Copy Orthologue tool. The genome sequence of C. sieboldii will be valuable for species identifications, ecological research, wood science, and applications such as tree breeding.
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Abe H, Fu D, Sato T, Tokumoto Y, Hyodo F, Katayama A
Journal of environmental management 371 123146 - 123146 2024年11月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Environmental Management
Overbrowsing by ungulates has degraded understory vegetation in worldwide forests. Understory degradation causes soil erosion and environmental degradation, causing mature tree decline. Although ungulate exclosure fences are installed to protect vegetation, their effectiveness in preventing tree decline associated with soil degradation remains unclear. We aimed to fill this gap on slopes of Mt. Shiraga, Japan, where sika deer have overbrowsed for >20 years. Tree-ring records in 1960–2022 for eight beeches per each of inside and outside fences were analyzed to compare stem basal area increment (BAI, cm<sup>−2</sup> yr<sup>−1</sup>) and trend change timings for BAI (i.e., break-point). Soil properties, exposed root height (ERH) as cumulative soil erosion index, and intrinsic water use efficiency (iWUE) as water limitation proxy were also compared. Compared with areas inside fences, areas outside fences had no understory vegetation, higher ERH, and higher soil hardness and moisture. BAI outside fences turned their growth trend from positive to negative since 2004, but not inside fences. Break-point of BAI outside fences matched the understory degradation period in the field. The long-term BAI trend (i.e., regression slope of BAI) after the break-point was negatively related to ERH but not to soil properties (e.g., soil hardness and moisture). Furthermore, BAI outside fences was negatively related to iWUE after the break-point, whereas BAI inside fences was not. These results indicate that the maintenance of understory by fencing prevents overbrowsing-associated mature tree decline through mitigating root exposure and related water limitation, despite the potential of water competition with understory.
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Yuji Tokumoto, Yuki Sakurai, Hayato Abe, Ayumi Katayama
Forest Ecology and Management 564 121993 - 121993 2024年7月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Elsevier BV
The increasing deer population has significantly altered the forest ecosystems. Deer browsing affects not only plant species diversity and composition but also other organisms indirectly, along with soil properties. However, the effects of deer grazing on the soil microbial community and the underlying mechanisms have not been well understood. To assess these effects, we compared the understory environment and soil microbial community inside and outside fences at Mt. Shiraga, where severe soil environmental degradation has occurred due to sika deer grazing. We selected 20 Fagus trees inhabiting areas within and outside the fences with similar topological features. Eleven environmental variables and both soil prokaryotic and fungal communities were compared between samples inside and outside the fences. The area inside the fence had significantly higher dwarf bamboo density and soil carbon (C) and nitrogen (N) content, whereas soils outside the fences had higher pH and bulk density. The diversity index of the fungal community, in terms of the number of amplicon sequence variants, inside the fence was higher than that outside, whereas that of the prokaryotic community did not differ between fences. Both prokaryotic and fungal communities differed between inside and outside fences. The prokaryotic community changed with the soil C/N ratio, and the relative abundance of oligotrophic bacteria increased with decreasing soil C/N ratio. The fungal community also changed with soil pH and dwarf bamboo density, with the relative abundances of symbiotrophic fungi and ectomycorrhizae increasing with increasing soil pH. Comparative analyses between inside and outside fence samples might provide information on soil microbial community changes with the changes in soil properties after deer grazing.
受賞 【 表示 ／ 非表示 】
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Top 10% of most-viewed paper published in Ecological Research between January 1, 2023 - December 31, 2023
2025年4月 Wiley Utility of commercial high‐resolution satellite imagery for monitoring general flowering in Sarawak, Borneo
Tomoaki Miura, Yuji Tokumoto, Nagai Shin, Kentaro K. Shimizu, Runi Anak Sylvester Pungga, Tomoaki Ichie
受賞区分：国内外の国際的学術賞
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Top 10 most-cited paper published in Ecological Research between January 1, 2023 and December 31, 2023
2025年3月 Wiley Utility of commercial high-resolution satellite imagery for monitoring general flowering in Sarawak, Borneo
Tomoaki Miura, Yuji Tokumoto, Nagai Shin, Kentaro K. Shimizu, Runi Anak Sylvester Pungga, Tomoaki Ichie
受賞区分：国内外の国際的学術賞
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Top 10 most-cited paper published in Ecological Research between 1st January 2022 – 31st December 2023
2024年4月 Wiley Utility of commercial high-resolution satellite imagery for monitoring general flowering in Sarawak, Borneo
Tomoaki Miura, Yuji Tokumoto, Nagai Shin, Kentaro K. Shimizu, Runi Anak Sylvester Pungga, Tomoaki Ichie
受賞区分：国内外の国際的学術賞
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2021年度Journal of Plant Research Best Paper賞
2021年5月 Journal of Plant Research (JPR) 編集委員会 Assessment of Polygala paniculata (Polygalaceae) characteristics for evolutionary studies of legume–rhizobia symbiosis
Yuji Tokumoto, Kayo Hashimoto, Takashi Soyano, Seishiro Aoki, Wataru Iwasaki, Mai Fukuhara, Tomomi Nakagawa, Kazuhiko Saeki, Jun Yokoyama, Hironori Fujita, Masayoshi Kawaguchi
受賞区分：国内外の国際的学術賞
科研費（文科省・学振・厚労省）獲得実績 【 表示 ／ 非表示 】
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下層植生消失によるブナの水・養分ストレスが土壌生物多様性と生態系機能に与える影響
研究課題/領域番号：23K25047 2024年04月 - 2026年03月
独立行政法人日本学術振興会 科学研究費基金 基盤研究(B)
担当区分：研究分担者
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下層植生消失によるブナの水・養分ストレスが土壌生物多様性と生態系機能に与える影響
研究課題/領域番号：22H03793 2022年04月 - 2026年03月
日本学術振興会 科学研究費補助金 基盤研究(B)
片山 歩美, 東 若菜, 徳本 雄史, 菱 拓雄, 久米 朋宣
担当区分：研究分担者
九州南部のブナ群生地では今、鹿により下層植生（ササ）が消失し、深刻な土壌流出、ブナの衰退や枯死、森林の裸地化が進んでいる。本研究は、下層植生消失がブナの水・養分ストレスに与える影響を解明し、ブナ衰退によるリター被覆の減少が土壌の生物多様性や生態系機能に与える影響を明らかにする。また、リター被覆が土壌環境の改善を介して、ブナのストレスおよび土壌の生物多様性・生態系機能を回復させるかを操作実験により確かめる。
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今年度、土壌侵食の指標である根の露出度合いが高いほど、ブナの成長は低下し、水利用効率が上がることを明らかにした。土壌水分はおおむね高かったことから、下層植生消失による土壌侵食が根の枯死を招き、給水が十分に行えていないことが考えられた。また、根の露出度合いと土壌特性の関係を調べたところ、侵食が起こっているところでは土壌炭素が低く、微生物呼吸が低いこと、真菌類の群集には影響を与えないが細菌類の多様性が変化することが明らかとなった。一方で、ササの存在する林分では真菌類の多様性が高いことが明らかとなった。
2022年8月にリター被覆操作前の土壌および樹木生態生理パラメーターを取得し、衰退しているブナでは水ストレスがあり、土壌微生物相は健全個体とは異なることが明らかとなった。2022年11月に健全木、衰退木それぞれ3個体にリター被覆実験を行った。
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成果発表としては、国際誌論文が1報、国際誌査読中論文が3報あり、関連する学会発表は3件あった。 -
東南アジアの植生回復に向けた先駆樹種の機能と遷移後期樹種との種間相互作用系の解明
研究課題/領域番号：22K05692 2022年04月 - 2026年03月
日本学術振興会 科学研究費基金 基盤研究(C)
徳本 雄史, 市榮 智明
担当区分：研究代表者
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高頻度・高空間分解能衛星による日本とボルネオの常緑広葉樹の種判別と広域マッピング
研究課題/領域番号：22K12352 2022年04月 - 2026年03月
日本学術振興会 科学研究費基金 基盤研究(C)
永井 信, 遠藤 拓洋, 徳本 雄史, 市榮 智明
担当区分：研究分担者
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トランスクリプトーム解析による東南アジア熱帯の群集レベルのフェノロジー現象の解明
研究課題/領域番号：19K15875 2019年04月 - 2022年03月
日本学術振興会 科学研究費助成事業 若手研究 若手研究
徳本 雄史
担当区分：研究代表者
本研究では東南アジア熱帯の林冠で見られるフタバガキ科、マメ科、カキ科の個体を対象として、フェノロジーと気象データ、そして発現遺伝子との関係から、種レベルかつ群集レベルのフェノロジー現象を明らかにすることを目的とした。調査期間中に降水量の低下と群集レベルの開花が起こり、調査対象の個体の多くが開花した。発現遺伝子の解析から、開花前に乾燥応答の遺伝子と低温応答の遺伝子のいずれかまたは両方の発現量が変化していた。これは同調開花のトリガーとされてきた乾燥と低温の２つが、複数の林冠樹種で発現遺伝子のレベルから確認されたことと、林冠樹種が機微な気象条件の変化で生物季節的な現象を起こしていることが示唆された。
