Estimation of photosynthetic dynamics in forests from daily measured fluorescence and PRI data with adjustment for canopy shadow fraction

0576443 - ÚVGZ 2024 RIV NL eng J - Článek v odborném periodiku
Kováč, Daniel - Novotný, Jan - Šigut, Ladislav - Ač, Alexander - Penuelas, Josep - Grace, John - Urban, Otmar
Estimation of photosynthetic dynamics in forests from daily measured fluorescence and PRI data with adjustment for canopy shadow fraction.
Science of the Total Environment. Roč. 898, NOV (2023), č. článku 166386. ISSN 0048-9697. E-ISSN 1879-1026
Grant CEP: GA MŠMT(CZ) EF16_019/0000797
Výzkumná infrastruktura: CzeCOS IV - 90248
Institucionální podpora: RVO:86652079
Klíčová slova: 3-fld * Daily dynamics * Fluorescence * LiDAR * Photochemical reflectance index * Shadow fraction
Obor OECD: Biophysics
Impakt faktor: 9.8, rok: 2022
Způsob publikování: Omezený přístup
https://www.sciencedirect.com/science/article/pii/S0048969723050118?via%3Dihub

We conducted year-long measurements of the photochemical reflectance index (PRI) and solar-induced fluorescence in the O2A oxygen band (SIFA) at a Norway spruce forest and a European beech forest to study relationships of these remote sensing variables to photosynthesis by trees in grown forest stands. Measured PRI and SIFA values were linked to changes in forest gross primary productivity (GPP) and light-use efficiency (LUE). Changes in the shadow fraction (& alpha,S) within tree crowns influenced PRI and fluorescence signals. In the spruce forest, the quantum yield of SIFA (FYSIFA) decreased around midday together with photosynthesis and GPP. Such decreases in FYSIFA were accompanied by an increase in the & alpha,S. In the beech forest, we detected an increase in FYSIFA together with a decrease in & alpha,S in the afternoon hours. The overall sensitivity of PRI to LUE was variable according to the season, presumably influenced by complex changes in photosynthetic pigments. PRI and FYSIFA showed weak correlations with canopy LUE, however, when considered together, the correlation was strengthened (R2 was 0.63 and 0.34 in spruce and beech forest, respectively). Our model predicting LUE dynamics includes a diurnal minimum of PRI and canopy & alpha,S to make allowances for seasonal changes in photosynthetic pigments and for diurnal variability of the shadow fraction in forests. The incorporation of these correcting factors allowed us to estimate LUE at R2 = 0.68 (spruce) and 0.53 (beech). The modeling equations appeared sensitive to the absorbed photosynthetically active radiation (APAR), but less sensitive to the GPP of these forests. Substituting pigments correction with introducing differential PRI (& UDelta,PRI) into the model did not significantly improve the LUE estimation across the season. Our results show that the joint use of PRI and fluorescence improves LUE and GPP estimation accuracy in both daily and seasonal observations.
Trvalý link: https://hdl.handle.net/11104/0346251