全国191か所の観測が捉えた森林の変化 ~長期観測データにより気候変動との関連が明らかに~

2026-10-27 大阪公立大学,国立環境研究所,九州大学,秋田県立大学,信州大学,森林総合研究所,北海道大学,東京農工大学,京都大学

大阪公立大学、国立環境研究所、九州大学などの研究グループは、日本全国191か所の森林調査区で蓄積された長期観測データを統合し、1950年代以降の森林構造と樹種構成の変化を分析した。対象は北方針葉樹林、落葉広葉樹林、温帯針葉樹林、常緑広葉樹林の4つの森林タイプである。各調査区の樹木の胸高断面積合計などを指標として、森林の変化と気温・降水量の推移、病虫害や獣害などの撹乱要因との関係を調べた。その結果、すべての森林タイプで構造や樹種構成に変化が確認され、気温上昇地域では森林の胸高断面積合計が増加する傾向がみられた。一方、北方針葉樹の優占度は低下し、落葉広葉樹の割合は増加しており、特に寒冷地域の森林で樹種の置き換わりが進んでいた。これらの結果は、温暖化に伴って暖かい気候を好む樹種が増える「好熱化」をおおむね支持する。ただし、降水量の変化や台風などの撹乱も影響しており、森林変化の要因は複合的である。

全国191か所の観測が捉えた森林の変化 ~長期観測データにより気候変動との関連が明らかに~
図1 日本列島で見られる4つの主要な森林バイオーム(写真:日浦 勉)
左より、北方針葉樹林・落葉広葉樹林・温帯針葉樹林・常緑広葉樹林

<関連情報>

長期モニタリングにより、日本の森林バイオーム構成における気候変動および撹乱に対する異なる反応が明らかになった Long-term monitoring reveals differential climate and disturbance responses in Japanese forest biome composition

Tetsuro Yoshikawa,Yayoi Takeuchi,Taku Kadoya,Tsutomu Enoki,Sakae Fujii,Atsuko S. Fukamachi,Mitsuru Hirota,Kazuhiko Hoshizaki,Naoki Iiyama,Yukio Ishikawa,Hiroki Itô,Hajime Kobayashi,Yasuo Konno,Hiroko Kurokawa,Akifumi Makita,Akira S. Mori,Dai Nagamatsu,Tohru Nakashizuka,Kanji Namikawa,Mahoko Noguchi…Tsutom Hiura
Forest Ecosystems  Available online: 20 August 2026,
DOI:https://doi.org/10.1016/j.fecs.2026.100531

Abstract

Tree community responses to climate change differ markedly among biomes, and multiple interacting drivers complicate interpretation. This study investigated structural and compositional changes across major forest biomes (boreal conifers, deciduous broadleaved trees, temperate conifers, and evergreen broadleaved trees) using extensive spatial and temporal forest community data. The analyzed dataset included 191 plots across Japan, spanning decades since the 1950s and encompassing old-growth and secondary forest age classes. For each plot, biome types were classified, and changes in tree communities were quantified. Forest structural shifts were evaluated using the total basal area of all trees, four tree functional types, and dominant species. Compositional shifts were assessed based on the relative dominance of each functional type. Associations between these changes and climatic conditions, climate change trends, and other potential forest disturbance drivers were analyzed. Results showed that forest structure and functional composition changed across all biomes, with structural change significantly linked to climatic trends. Distinct response patterns to climatic variables emerged depending on biome and forest age. In old-growth forests, structural change rates were positively associated with the mean annual temperature change and negatively associated with the annual precipitation change. Structural change declined notably in southwestern regions with increased annual precipitation, likely due to intensified typhoon disturbance. Boreal conifer functional types declined markedly in relative dominance in old-growth forests and were replaced by deciduous broadleaved trees. Additionally, evergreen broadleaved types increased in some deciduous broadleaved old-growth forests. Overall, these findings align with thermophilization and indicate a broader, ongoing biome shift.

1304森林環境
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