Simulating emission and scattering of solar-induced chlorophyll fluorescence at far-red band in global vegetation with different canopy structures

Qiu, Bo; Chen, Jing M.; Ju, Weimin; Zhang, Qian; Zhang, Yongguang

doi:10.1016/j.rse.2019.111373

Cited by 40 publications

(35 citation statements)

References 59 publications

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“…Judging from our results, however, the improvement in spatial patterns goes together with a degradation of temporal relationships. In contrast to our site-level findings, Qiu et al (2019) reported consistent and partly considerable improvements in the temporal SIF -GPP relationships when normalizing for f esc based on global process-based simulations. However, small to moderate improvements and partly even degradation of results were found when applying the f esc normalization to OCO-2 SIF retrievals and evaluating the temporal correlation to FLUXCOM GPP (Qiu et al, 2019).…”

Section: Implications For Large Scale Gpp Estimationcontrasting

confidence: 99%

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

Dechant

Ryu

Badgley

et al. 2020

Remote Sensing of Environment

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203

166

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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 f esc to the seasonal dynamics of the photosynthetic light use efficiency (LUE P), while the estimated physiological SIF yield was almost entirely uncorrelated to LUE P 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 (NIR V) 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.

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Section: Implications For Large Scale Gpp Estimationcontrasting

confidence: 99%

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

Dechant

Ryu

Badgley

et al. 2020

Remote Sensing of Environment

Self Cite

203

166

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“…In addition, multiple scattering SIF is also simulated to account for the scattering process within the canopy. The scaling of leaf-level fluorescence emission to the canopy is based on a novel scheme for single-layer models which accounts for canopy scattering and extinction from sunlit and shaded leaves (Qiu et al, 2019). This scaling scheme is an effective approach to simulate the radiative transfer of SIF for a given canopy structure.…”

Section: Bepsmentioning

confidence: 99%

Wide discrepancies in the magnitude and direction of modeled solar-induced chlorophyll fluorescence in response to light conditions

et al. 2020

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Abstract. Recent successes in passive remote sensing of far-red solar-induced chlorophyll fluorescence (SIF) have spurred the development and integration of canopy-level fluorescence models in global terrestrial biosphere models (TBMs) for climate and carbon cycle research. The interaction of fluorescence with photochemistry at the leaf and canopy scales provides opportunities to diagnose and constrain model simulations of photosynthesis and related processes, through direct comparison to and assimilation of tower, airborne, and satellite data. TBMs describe key processes related to the absorption of sunlight, leaf-level fluorescence emission, scattering, and reabsorption throughout the canopy. Here, we analyze simulations from an ensemble of process-based TBM–SIF models (SiB3 – Simple Biosphere Model, SiB4, CLM4.5 – Community Land Model, CLM5.0, BETHY – Biosphere Energy Transfer Hydrology, ORCHIDEE – Organizing Carbon and Hydrology In Dynamic Ecosystems, and BEPS – Boreal Ecosystems Productivity Simulator) and the SCOPE (Soil Canopy Observation Photosynthesis Energy) canopy radiation and vegetation model at a subalpine evergreen needleleaf forest near Niwot Ridge, Colorado. These models are forced with local meteorology and analyzed against tower-based continuous far-red SIF and gross-primary-productivity-partitioned (GPP) eddy covariance data at diurnal and synoptic scales during the growing season (July–August 2017). Our primary objective is to summarize the site-level state of the art in TBM–SIF modeling over a relatively short time period (summer) when light, canopy structure, and pigments are similar, setting the stage for regional- to global-scale analyses. We find that these models are generally well constrained in simulating photosynthetic yield but show strongly divergent patterns in the simulation of absorbed photosynthetic active radiation (PAR), absolute GPP and fluorescence, quantum yields, and light response at the leaf and canopy scales. This study highlights the need for mechanistic modeling of nonphotochemical quenching in stressed and unstressed environments and improved the representation of light absorption (APAR), distribution of light across sunlit and shaded leaves, and radiative transfer from the leaf to the canopy scale.

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“…The interfering effects of at canopy scale have not been considered explicitly. They are implicit in the relations of SIF,GPP(APAR) (Qiu et al, 2019). When accounted for, they may provide a better estimate of the correlation attributable to the physiological response of photosystems (i.e., SIF,GPP(APAR,fesc) > 0.27).…”

Section: Physical Basis For the Sif-gpp Relationshipmentioning

confidence: 99%

“…Therefore, they must, in turn, affect the success of remote sensing relationships for SIF-GPP (Yang and Van der Tol, 2018). Likewise, these factors also affect the variability of the APAR-GPP relationship (Dechant et al, 2020;Qiu et al, 2019), and the LUE-GPP relationship (e.g., Middleton et al, 2019).…”

Section: Physically and Physiologically Joint Effects On The Sif-gpp mentioning

confidence: 99%

“…Furthermore, they reported that their estimates of physiological SIF yield (Φ = SIF/APAR/ ) showed no clear seasonal patterns and were unlikely to contribute to the positive correlation between GPP and far-red SIF. In contrast, Qiu et al (2019) reported that the similar correction of SIF for canopy scattering resulted in a better correlation to GPP, and Yang et al (2020) showed that the estimates of canopy-scale light use efficiency of fluorescence (Φ ) were clearly higher in young and mature stages than for the senescent stages, and were correlated with Φ . The inconsistent findings could partly be caused by considerable uncertainties in the estimates of and Φ , especially since the physiological indicators (Φ and Φ ) are still contaminated by canopy structural effects (Yang et al, 2020).…”

Section: Introductionmentioning

confidence: 98%

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Unravelling the physical and physiological basis for the solar-induced chlorophyll fluorescence and photosynthesis relationship

Yang¹,

Tol²,

Campbell³

et al. 2020

Preprint

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Abstract. Estimates of the gross terrestrial carbon uptake exhibit large uncertainties. Sun-induced chlorophyll fluorescence (SIF) has an apparent near-linear relationship with gross primary production (GPP). This relationship will potentially facilitate the monitoring of photosynthesis from space. However, the exact mechanistic connection between SIF and GPP is still not clear. To explore the physical and physiological basis for their relationship, we used a unique dataset comprising continuous field measurements of leaf and canopy fluorescence and photosynthesis of corn over a growing season. We found that, at canopy scale, the positive relationship between SIF and GPP was dominated by absorbed photosynthetically active radiation (APAR), which was equally affected by variations in incoming radiation and changes in canopy structure. After statistically controlling these underlying physical effects, the remaining correlation between far-red SIF and GPP due solely to the functional link between fluorescence and photosynthesis at the photochemical level was much weaker. Active leaf-level fluorescence measurements revealed a moderate correlation between the efficiencies of fluorescence emission and photochemistry for sunlit leaves but a weak correlation for shaded leaves. Differentiating sunlit and shaded leaves in the light use efficiency (LUE) models for SIF and GPP facilitates a better understanding of the SIF-GPP relationship at different environmental and canopy conditions. Leaf-level fluorescence measurements also demonstrated that the sustained thermal dissipation efficiency dominated the seasonal energy partitioning while the reversible heat dissipation dominated the diurnal leaf energy partitioning. These diurnal and seasonal variations in heat dissipation underlie, and are thus responsible for, the observed remote sensing-based link between far-red SIF and GPP.

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Simulating emission and scattering of solar-induced chlorophyll fluorescence at far-red band in global vegetation with different canopy structures

Cited by 40 publications

References 59 publications

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

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

Wide discrepancies in the magnitude and direction of modeled solar-induced chlorophyll fluorescence in response to light conditions

Unravelling the physical and physiological basis for the solar-induced chlorophyll fluorescence and photosynthesis relationship

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