Measurement and Analysis of Bidirectional SIF Emissions in Wheat Canopies

Liu, Liangyun; Liu, Xinjie; Wang, Zhihui; Zhang, Bing

doi:10.1109/tgrs.2015.2504089

Cited by 79 publications

(65 citation statements)

References 46 publications

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“…The SIF observation might be also impacted by the directionality (characterized by the bidirectional reflectance distribution function), although observing from the nadir partially reduces the effect. Multiangle observations of SIF could be helpful to characterize the uncertainties of directional effects (Liu et al, ). Additionally and importantly, the reabsorption of emitted SIF was not taken into account in this current study (Gitelson, Buschmann, & Lichtenthaler, ; Porcar‐Castell et al, ), implying a potential gap between the observed SIF and the true SIF y (SIF = APAR × SIF y × f esc , in which f esc accounts for the fraction of SIF photons escaping from the canopy to be detected).…”

Section: Discussionmentioning

confidence: 99%

Sun‐Induced Chlorophyll Fluorescence, Photosynthesis, and Light Use Efficiency of a Soybean Field from Seasonally Continuous Measurements

et al. 2018

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Recent development of sun‐induced chlorophyll fluorescence (SIF) technology is stimulating studies to remotely approximate canopy photosynthesis (measured as gross primary production, GPP). While multiple applications have advanced the empirical relationship between GPP and SIF, mechanistic understanding of this relationship is still limited. GPP:SIF relationship, using the standard light use efficiency framework, is determined by absorbed photosynthetically active radiation (APAR) and the relationship between photosynthetic light use efficiency (LUE) and fluorescence yield (SIFy). While previous studies have found that APAR is the dominant factor of the GPP:SIF relationship, the LUE:SIFy relationship remains unclear. For a better understanding of the LUE:SIFy relationship, we deployed a ground‐based system (FluoSpec2), with an eddy‐covariance flux tower at a soybean field in the Midwestern U.S. during the 2016 growing season to collect SIF and GPP data simultaneously. With the measurements categorized by plant growth stages, light conditions, and time scales, we confirmed that a strong positive GPP:SIF relationship was dominated by an even stronger linear SIF:APAR relationship. By normalizing both GPP and SIF by APAR, we found that under sunny conditions our soybean field exhibited a clear positive SIFy:APAR relationship and a weak negative LUE:SIFy relationship, opposite to the positive LUE:SIFy relationship reported previously in other ecosystems. Our study provides a first continuous SIF record over multiple growth stages for agricultural systems and reveals a distinctive pattern related to the LUE:SIFy relationship compared with previous work. The observed positive relationship of SIFy:APAR at the soybean site provides new insights of the previous understanding on the SIF's physiological implications.

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Section: Discussionmentioning

confidence: 99%

Sun‐Induced Chlorophyll Fluorescence, Photosynthesis, and Light Use Efficiency of a Soybean Field from Seasonally Continuous Measurements

et al. 2018

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“…L2018 used all modes in the OCO-2 product, which have different VZAs and hence different ranges of SIF (Figure 1a,b). Similar to canopy reflectance, there are noticeable angular variations of SIF (Liu, Liu, Wang, & Zhang, 2015;van der Tol, Verhoef, Timmermans, Verhoef, & Su, 2009). This variation has effect on the SIF-GPP relationship (He et al, 2017G).…”

mentioning

confidence: 99%

Angle matters: Bidirectional effects impact the slope of relationship between gross primary productivity and sun‐induced chlorophyll fluorescence from Orbiting Carbon Observatory‐2 across biomes

Zhang

Joiner

et al. 2018

Global Change Biology

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Written Summary: It is important to understand how sun-sensor geometry affects satellite sun-induced fluorescence (SIF) in order to take full advantage of these measurements, particularly given their close relationship with gross primary production (GPP). We displayed the bidirectionality of SIF at different viewing zenith angles in the solar principal plane and observed a clear bowl shape of SIF from the backward to forward scattering directions. Therefore, it is important to consider the bidirectionality of SIF when using OCO-2 SIF data to evaluate the SIF-GPP relationship.

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“…Following Chen and Cihlar [], the C is set to 12.5° for forests and 8.33° for other land cover types. Currently, there are only few papers showing clear contrasts between SIF s and SIF sh for sparse canopies [ Liu et al , ; Pinto et al , ]. The ratio β is estimated to be 9 from the direct SIF mapping in the very high resolution (sub–leaf level) at the sunny conditions [ Pinto et al , ].…”

Section: Methodsmentioning

confidence: 99%

Angular normalization of GOME‐2 Sun‐induced chlorophyll fluorescence observation as a better proxy of vegetation productivity

Chen

Liu

et al. 2017

Geophysical Research Letters

100

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Sun‐induced chlorophyll fluorescence (SIF) has been regarded as a promising proxy for gross primary productivity (GPP) over land. Considerable uncertainties in GPP estimation using remotely sensed SIF exist due to variations in the Sun‐satellite view observation geometry that could induce unwanted variations in SIF observation. In this study, we normalize the far‐red Global Ozone Monitoring Experiment‐2 SIF observations on sunny days to hot spot direction (SIFh) to represent sunlit leaves and compute a weighted sum of SIF (SIFt) from sunlit and shaded leaves to represent the canopy. We found that SIFh is better correlated with sunlit GPP simulated by a process‐based ecosystem model and SIFt is better correlated with the simulated total GPP than the original SIF observations. The coefficient of determination (R2) are increased by 0.04 ± 0.03, and 0.07 ± 0.04 on a global average using SIFh and SIFt, respectively. The most significant increases of the R2 (0.09 ± 0.04 for SIFt and 0.05 ± 0.03 for SIFh) appear in deciduous broadleaf forests.

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Measurement and Analysis of Bidirectional SIF Emissions in Wheat Canopies

Cited by 79 publications

References 46 publications

Sun‐Induced Chlorophyll Fluorescence, Photosynthesis, and Light Use Efficiency of a Soybean Field from Seasonally Continuous Measurements

Sun‐Induced Chlorophyll Fluorescence, Photosynthesis, and Light Use Efficiency of a Soybean Field from Seasonally Continuous Measurements

Angle matters: Bidirectional effects impact the slope of relationship between gross primary productivity and sun‐induced chlorophyll fluorescence from Orbiting Carbon Observatory‐2 across biomes

Angular normalization of GOME‐2 Sun‐induced chlorophyll fluorescence observation as a better proxy of vegetation productivity

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