Effect of CO2 fertilization on photosynthetic function and forest structure through interactions with mycorrhizal fungi

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K15559
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 40010:Forest science-related
• Research Institution: National Institute for Environmental Studies
• Principal Investigator: Akaji Yasuaki 国立研究開発法人国立環境研究所, 生物多様性領域, 主任研究員 (50810256)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 植物-土壌フィードバック / 光合成 / 菌根菌 / ブナ / 冷温帯 / 気候変動

Outline of Final Research Achievements

Photosynthetic capacity is known to be often down-regulated when plants are exposed to high CO2 concentration for a certain period of time. To elucidate the mechanism, this study conducted a pot experiment for Fagus crenata, which is a dominant species in cool-temperate forests in Japan. The seedlings at the high CO2 concentration (700 ppm) exhibited lower Jmax (maximum electron transport rate) and Vcmax (maximum carboxylation rate) than those at control. Only at the high CO2 environment, moreover, Jmax:Vcmax ratio was positively correlated to the percentage of ectomycorrhiza formation. This result implies that the seedlings at the high CO2 allocated lower resource (nitrogen) to rubisco, resulting in an increase in the intensity of the down-regulation of photosynthesis.

Free Research Field

森林生態学

Academic Significance and Societal Importance of the Research Achievements

本研究では高CO2環境における光合成能力の低下（すなわち，光合成のダウンレギュレーション）が外生菌根の形成率といった地下部の形質と関連があることを示している．この結果は今後の植物の光合成能の変化を予測するモデルの発展に寄与する可能性がある．さらに，ブナの成長や光合成能力は他種成木土壌（イタヤカエデ等の林冠木近傍から採取した土壌）よりも同種成木土壌（ブナ林冠木近傍から採取した土壌）で生育させた場合に低く，この傾向は生育する大気CO2濃度で変化しなかったという本研究の結果は，今後のブナの更新パターンやブナ林の構造を予測するのに役立つと考えられる．