日本地球惑星科学連合2022年大会

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セッション記号 A (大気水圏科学) » A-CG 大気海洋・環境科学複合領域・一般

[A-CG39] 陸域生態系の物質循環

2022年5月26日(木) 15:30 〜 17:00 展示場特設会場 (2) (幕張メッセ国際展示場)

コンビーナ:加藤 知道(北海道大学農学研究院)、コンビーナ:市井 和仁(千葉大学)、伊勢 武史(京都大学フィールド科学教育研究センター)、コンビーナ:寺本 宗正(鳥取大学乾燥地研究センター)、座長:伊勢 武史(京都大学フィールド科学教育研究センター)

15:45 〜 16:00

[ACG39-08] Estimation of leaf-level SIF from observed SIF for the reliable GPP calculation by remote sensing data in a cool temperate-deciduous broadleaf forest

*酒井 佑槙1小林 秀樹1加藤 知道2両角 友喜2中島 直久3奈佐原 顕郎4秋津 朋子5村山 昌平6野田 響7、村岡 裕由8、大塚 俊之8、吉竹 晋平9、彦坂 幸毅10押尾 晴樹11吉田 幸生7 (1.国立研究開発法人海洋研究開発機構、2.北海道大学農学研究院、3.帯広畜産大学、4.筑波大学生命環境系、5.国立研究開発法人宇宙航空研究開発機構、6.国立研究開発法人産業技術総合研究所 、7.国立研究開発法人国立環境研究所、8.岐阜大学流域圏科学研究センター、9.早稲田大学 教育・総合科学学術院、10.東北大学大学院生命科学研究科、11.東京工業大学 環境・社会理工学院)

キーワード:太陽子誘発クロロフィル蛍光、光合成、放射伝達モデル

Photosynthesis and ecosystem respiration are major processes to control the global carbon cycle. Solar-induced fluorescence (SIF) has been extensively used to estimate the Gross Primary production (GPP) at the ecosystem scale because the observed SIF (OSIF) exhibits a good correlation with net photosynthesis, which is quantified by the gas exchange monitoring method at the leaf level and by the eddy covariance method at the ecosystem scale. The canopy-scale SIF can be observed by ground-based spectroscopy and satellite sensors (e.g. GOSAT, GOSAT-2, OCO-2, etc.). These satellite-derived SIF data have the potential to estimate the global GPP because fluorescence occurs in the photosystem and it reflects the photosynthesis activity.
In the modeling approach, the relationship between GPP and SIF at leaf scale has been expressed by the energy distribution model which uses quantum yield against absorbed energy and rate coefficients. The model expresses the energy distribution at the leaf level. Thus, it is necessary to calculate the leaf-level SIF(LSIF) from OSIF (which is ecosystem-scale) to estimate the GPP, however, there are several uncertainties in the calculation process.
In this study, we focus on the three factors in the uncertainties; the contribution rate of OSIF to broad-band SIF, the fraction of emissions from photosystem (PS) II, and escape ratio to observation direction from the canopy. These factors are important in the calculation of LSIF from OSIF. However, it is difficult to observe these factors at the ecosystem scale. Thus, we estimate the factors using observable index, especially Green Red vegetation index (GRVI) and absorbed photosynthetically active radiation (APAR). In our method, we assume that the LSIF bears the linear relationship with OSIF and estimate the seasonal variation of the coefficient and intercept in the formula using GRVI and APAR. In addition, we validate the parameter values using observation data in a cool-temperate deciduous forest in Takayama, central Japan (AsiaFlux: JP-TKY) at ground observation and satellite observation by GOSAT.
As a result, we confirmed that the calibrated model showed better agreement with ground-observed GPP than photosynthesis models (De Pury and Farqhuhar’s model). From the comparison with satellite-observed GPP, our estimation shows similar seasonal variation although the ratio between LSIF and OSIF is validated by ground observation data. Thus, our method can apply to the satellite-based SIF and has the potential for large-scale estimation of GPP.