Process-based modeling of chlorophyll fluorescence and photosynthesis

Even though fluorescence and photosynthesis are physiologically related, a number of external parameters such as the intensity of the illumination flux, air temperature or the structure of the canopy must be considered for a proper interpretation of the fluorescence data and their optimal exploitation as a proxy for GPP. Accounting for such factors in the exploitation of space-based fluorescence measurements involves the use of mechanistic models able to parameterize photosynthesis, fluorescence and existing driving factors in a systematic way.

The SCOPE (Soil Canopy Observation, Photochemistry and Energy Fluxes) photosynthesis and fluorescence coupled model (Van der Tol et al. 2009), developed, maintained and made freely available by Christiaan van der Tol at ITC/University of Twente is able to describe leaf-level photosynthesis and fluorescence processes as well as their upscaling to the top-of-canopy level. We use SCOPE for the interpretation of global fluorescence data sets and for sensitivity analysis dealing with the connection between fluorescence and photosynthetic parameters such as gross primary production and photosynthetic capacity.

Mechanistic modeling of photosynthesis and chlorophyll fluorescence. (Top) Simulations of gross primary production (GPP) and sun-induced fluorescence (SIF) with the SCOPE (Soil Canopy Observation, Photochemistry and Energy Fluxes) photoynthesis and fluorescence model (Van der Tol et al., 2009) (figure by Yongguang Zhang). (Bottom) Estimation of crop photosyntetic capacity (Vcmax) through the inversion of real GOME-2 fluorescence data from with the SCOPE model (figure from Zhang et al., 2014).