Canopy structure explains the relationship between photosynthesis and sun-induced chlorophyll fluorescence in crops

REMOTE SENSING OF ENVIRONMENT

卷:241

Article

Dechant, Benjamin¹  Ryu, Youngryel¹  Badgley, Grayson²  Zeng, Yelu²  Berry, Joseph A.²  Zhang, Yongguang³  Goulas, Yves⁴  Li, Zhaohui³  Zhang, Qian³  Kang, Minseok⁵  Li, Ji³  Moya, Ismael⁴ 

[1] Seoul Natl Univ, Dept Landscape Architecture & Rural Syst Engn, Seoul, South Korea

[2] Carnegie Inst Sci, Dept Global Ecol, Stanford, CA USA

[3] Nanjing Univ, Int Inst Earth Syst Sci, Jiangsu Prov Key Lab Geog Informat Sci & Technol, Nanjing, Peoples R China

[4] Ecole Polytech, Dynam Meteorol Lab, Palaiseau, France

[5] Natl Ctr AgroMeteorol, Seoul, South Korea

关键词: Sun-induced chlorophyll fluorescence;    Light use efficiency;    Photosynthesis;    Near-infrared reflectance of vegetation;    NIRv;    Escape fraction;    Canopy scattering;    Canopy structure;   

DOI  :  10.1016/j.rse.2020.111733

来源: Elsevier

【 摘 要 】

Remote sensing of far-red sun-induced chlorophyll fluorescence (SIF) has emerged as an important tool for studying gross primary productivity (GPP) at the global scale. However, the relationship between SIF and GPP at the canopy scale lacks a clear mechanistic explanation. This is largely due to the poorly characterized role of the relative contributions from canopy structure and leaf physiology to the variability of the top-of-canopy, observed SIF signal. In particular, the effect of the canopy structure beyond light absorption is that only a fraction (f(esc)) of the SIF emitted from all leaves in the canopy can escape from the canopy due to the strong scattering of near-infrared radiation. We combined rice, wheat and corn canopy-level in-situ datasets to study how the physiological and structural components of SIF individually relate to measures of photosynthesis. At seasonal time scales, we found a considerably strong positive correlation (R-2 = 0.4-0.6) of fesc to the seasonal dynamics of the photosynthetic light use efficiency (LUEP), while the estimated physiological SIF yield was almost entirely uncorrelated to LUEP both at seasonal and diurnal time scales, with the partial exception of wheat. Consistent with these findings, the canopy structure and radiation component of SIF, defined as the product of APAR and f(esc), explained the relationship of observed SIF to GPP and even outperformed GPP estimation based on observed SIF at two of the three sites investigated. These results held for both half-hourly and daily mean values. In contrast, the total emitted SIF, obtained by normalizing observed SIF for f(esc), improved only the relationship to APAR but considerably decreased the correlation to GPP for all three crops. Our findings demonstrate the dominant role of canopy structure in the SIF-GPP relationship and establish a strong, mechanistic link between the near-infrared reflectance of vegetation (NIRV) and the relevant canopy structure information contained in the SIF signal. These insights are expected to be useful in improving remote sensing based GPP estimates.

【 授权许可】

Free