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Harvard Forest Symposium Abstract 2017

  • Title: Solar induced fluorescence as a proxy for photosynthesis
  • Primary Author: Jim Tang (Marine Biological Laboratory)
  • Additional Authors: Zhunqiao Liu (); Hualei Yang (Marine Biological Laboratory)
  • Abstract:

    There is an emerging need to understand the variation in the relationship between solar induced fluorescence (SIF) and canopy photosynthesis as the satellite-based SIF data are being widely used to map the regional and global gross primary production (GPP). Without mechanistic understanding of this relationship and its variation diurnally and seasonally at the leaf to canopy scales, the satellite SIF cannot be fully interpreted and validated. We measured chlorophyll fluorescence and SIF at the leaf scale using a traditional pulse amplitude modulation fluorometer and a novel portable SIF system, respectively, and SIF at the canopy scale using a newly developed SIF measurement system at the Harvard Forest throughout the growing season. We also measured photosynthesis at the leaf scale and GPP from the eddy covariance data. We retrieved the full-wavelength SIF spectrum and calculated the red and infrared SIF peaks. We upscaled the leaf SIF to canopy SIF using a canopy radiative transfer model and then compared leaf-upscaled canopy SIF, directly measured canopy SIF, and canopy GPP. Our results suggested that directly measured canopy-SIF correlated well with canopy GPP at the seasonal pattern, but the leaf-upscaled canopy-SIF better reflected the diurnal pattern of GPP. We built a SIF model to simulate GPP that counts for the variation of the relationship between SIF and GPP diurnally and seasonally.

  • Research Category: Forest-Atmosphere Exchange