Abstract
Remote measurement of solar-induced chlorophyll fluorescence (SIF) has opened a new perspective to assess plant actual photosynthesis at larger, ecologically relevant scales. Several recent researches have demonstrated the strong link between satellite based SIF and gross primary production (GPP) at large scales. However, understanding the underling mechanisms between SIF and GPP remains challenging before SIF used as a robust constraint for estimating GPP. In this study, we used a combination of remotely sensed data together with model analysis to assess the impact factors that determining the SIF-GPP relationship. We found that the Global Ozone Monitoring Experiment–2 (GOME-2) SIF is spatially corresponded to the Moderate Resolution Imaging Spectroradiometer (MODIS) product for GPP. We also noticed that the SIF-GPP relationship was ecosystem-specific and influenced by land surface temperature. The former is due to some structural and physiological characteristics related to each ecosystem and the latter can be attributed to the biochemical process influenced by temperature conditions. Our analysis using Soil-Canopy Observation of Photochemistry and Energy fluxes (SCOPE) model also indicated the SIF-GPP relationship was complex and affected by some factors like shortwave irradiance, chlorophyll content and LAI. As SIF and GPP are influenced by a combination of several factors under natural conditions, we concluded that the simply linear regression relationship between SIF and GPP may be applicable only for some certain conditions and the their relationship may not be linear over natural conditions. Based on our analysis, we then suggested that dedicated strategies were required to compensate for the factors affecting SIF-GPP relationship before using SIF to estimate global GPP. The findings of this study contributes to a better understanding of the information inherent in remotely sensed SIF and its functional relationship to GPP.
Highlights
Plant photosynthesis is an important process in terrestrial ecosystem which mediates gas and energy exchanges in the atmosphere-biosphere system [1,2].As the underlying process for plant growth, photosynthesis serves as an essential indicator of plant efficiency and agricultural management practices [3,4]
The GOME2 platform can provide long-term Solar-Induced Chlorophyll Fluorescence (SIF) data when compared with the Orbiting Carbon Observatory-2 (OCO-2) which is launched in 2014.By considering data availability, Photosynthesiscan be represented by a light-use efficiency theory [44]: gross primary productivity (GPP)= Fraction of Photosynthetically Active Radiation (FPAR) × PAR ×ε P
We found the Global Ozone Monitoring Experiment–2 (GOME-2) SIF is consistently related to the Moderate Resolution Imaging Spectroradiometer (MODIS) GPP
Summary
Plant photosynthesis is an important process in terrestrial ecosystem which mediates gas and energy exchanges in the atmosphere-biosphere system [1,2].As the underlying process for plant growth, photosynthesis serves as an essential indicator of plant efficiency and agricultural management practices [3,4]. Net photosynthesis can be quantified at leaf scale by monitoring CO2 exchange using chamber enclosure systems combined with infrared gas analyzers [5], and at ecosystem scale using flux towers and eddy covariance techniques [6,7] These measurements are difficult to extend to large scales due to the relatively sparse observations and the spatial heterogeneous. Estimation of GPP is often linked with the accuracy of several physiologic and biochemical parameters, such as Leaf Area Index (LAI) and Fraction of Photosynthetically Active Radiation (FPAR), which are generally derived using reflectance-based indices [17].
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