| Summary: | We measured dynamics of solar-induced chlorophyll fluorescence at telluric oxygen absorption bands O<sub>2</sub>A and O<sub>2</sub>B in evergreen spruce and deciduous beech forests. Seasonal variations in fluorescence emissions were compared with NDVI. Daily changes in fluorescence emissions were compared with canopy shadow fraction (α<sub>S</sub>) dynamics, which showed impact of branch and leaf positions on detected fluorescence signals based on comparison with canopy height model. Absorbed photosynthetically active radiation (APAR) was recognized as a large determinant of fluorescence changes within the O<sub>2</sub>A band (SIFA), with R<sup>2</sup> > 0.68. Fluorescence within the O<sub>2</sub>B band was more directly linked to NDVI. Although, the seasonal dynamics of fluorescence within the O<sub>2</sub>B band (SIFB) were similar to SIFA in the spruce forest. In the beech forest, SIFB showed different seasonal dynamics as compared with SIFA. SIFA in the spruce forest showed a relationship to gross primary productivity (GPP), with R<sup>2</sup> = 0.48, and a relationship of R<sup>2</sup> = 0.37 was estimated for the SIFA-GPP connection in the beech forest. SIFB was better linked to seasonal GPP in the beech forest, but with a negative slope in the relationship with R<sup>2</sup> = 0.61. We have shown that measurements of passive fluorescence signals at telluric oxygen absorption bands can contribute to understanding to photosynthesis processes in forest canopies.
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