Sun-Induced Fluorescence's Correlation to Carbon-Flux Increases When Raw Data is Adjusted to Account for Vegetation Biochemistry and Structure.

Bontempo, Edgard; Valeriano, D. M.

doi:10.1002/essoar.10501587.2

Cited by 2 publications

(4 citation statements)

References 22 publications

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“…However, preliminary results from another study testing different biochemistry-and structure-related adjustments to SIF has found that the product of SIF by a proxy of f APAR showed the highest observed correlation to FLUXNET GPP data in comparison to various tested formulations [66]. The findings of that study suggest that SIF is not proportional to LUE by itself but rather to the instantaneous light-use efficiency under a given light incidence level (i.e., PAR * LUE).…”

Section: Land Cover Classification Datamentioning

confidence: 79%

Section: Linear Mixed Models and Our Adjustments To Sifmentioning

confidence: 99%

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Adjustments to SIF Aid the Interpretation of Drought Responses at the Caatinga of Northeast Brazil

Bontempo¹,

Dalagnol²,

Ponzoni³

et al. 2020

Preprint

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Sun-Induced chlorophyll Fluorescence (SIF) relates directly to photosynthesis yield and stress but there are still uncertainties in its interpretation. Most of these uncertainties concern the influences of the emitting vegetation’s structure (e.g., leaf angles, leaf clumping) and biochemistry (e.g., chlorophyll content, other pigments) on the radiative transfer of fluorescent photons. The Caatinga is a large region at northeast Brazil of semiarid climate and heterogeneous vegetation, where such biochemical and structural characteristics can vary greatly even within a single hectare. With this study we aimed to characterize eleven years of SIF seasonal variation from Caatinga vegetation (2007 to 2017) and to study its responses to a major drought in 2012. Orbital SIF data from the instrument GOME-2 was used along with MODIS MAIAC EVI and NDVI. Environmental data included precipitation rate (TRMM), surface temperature (MODIS) and soil moisture (ESA CCI). To support the interpretation of SIF responses we have used red and far-red SIF adjusted by the Sun’s zenith angle (SIF-SZA) and by daily Photosynthetically Active Radiation (dSIF). Furthermore, we have also adjusted SIF through two contrasting formulations using NDVI data as proxy for structure and biochemistry, based on previous leaf-level and landscape level studies: SIF-Yield and SIF-Prod. Data was tested with time-series decomposition, rank correlation, spatial correlation and Linear Mixed Models (LMM). Results show that GOME-2 SIF and adjusted SIF formulations responded consistently to the observed environmental variation and showed a marked decrease in SIF emissions in response to a 2012 drought, that was generally larger than the corresponding NDVI and EVI decreases. Drought sensitivity of SIF, as inferred from LMM slopes, was correlated to land cover at different regions of the Caatinga. This is the first study to show correlation between landscape-level SIF and an emergent property of ecosystems (i.e., resilience), showcasing the value of remotely sensed fluorescence for ecological studies.

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Section: Land Cover Classification Datamentioning

confidence: 79%

Section: Linear Mixed Models and Our Adjustments To Sifmentioning

confidence: 99%

Adjustments to SIF Aid the Interpretation of Drought Responses at the Caatinga of Northeast Brazil

Bontempo¹,

Dalagnol²,

Ponzoni³

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…The SIF FR -Prod adjustment, based on the classic productivity equation of Monteith and Moss [62,63], already shown in a preliminary study to increase the correlation between GOME-2 SIF and FLUXNET GPP across diverse vegetation types [66], yielded significant improvements on LMM goodness-of-fit in relation to standard SIF (Table 3). However, due to the substantial increase it caused in the effect size of the Ecoregion factor on tested LMMs (Table 2) and, considering that this effect encapsulates part of the structural variability between the different ecoregions, we conjecture that SIF FR -Prod may be "double-counting" the influence of emitting vegetation as it is calculated by multiplying SIF by NDVI and both variables are strongly influenced by vegetation structure and biochemistry.…”

Section: Linear Mixed Models and Our Adjustments To Sifmentioning

confidence: 94%

“…This classic equation has been frequently used to estimate GPP through the LUE-paradigm [65] and SIF has been proposed as a suitable proxy for LUE [2,10], although studies testing this proposition have reached confounding results [11,59]. However, preliminary results from another study testing different biochemistry-and structure-related adjustments to SIF has found that the product of SIF by a proxy of f APAR showed the highest observed correlation to FLUXNET GPP data in comparison to various tested formulations [66]. The findings of that study suggest that SIF is not proportional to LUE by itself but rather to the instantaneous light-use efficiency under a given light incidence level (i.e., PAR * LUE).…”

Section: Sun-induced Fluorescencementioning

confidence: 99%

Adjustments to SIF Aid the Interpretation of Drought Responses at the Caatinga of Northeast Brazil

et al. 2020

Self Cite

View full text Add to dashboard Cite

Sun-Induced chlorophyll Fluorescence (SIF) relates directly to photosynthesis yield and stress but there are still uncertainties in its interpretation. Most of these uncertainties concern the influences of the emitting vegetation’s structure (e.g., leaf angles, leaf clumping) and biochemistry (e.g., chlorophyll content, other pigments) on the radiative transfer of fluorescent photons. The Caatinga is a large region in northeast Brazil of semiarid climate and heterogeneous vegetation, where such biochemical and structural characteristics can vary greatly even within a single hectare. With this study we aimed to characterize eleven years of SIF seasonal variation from Caatinga vegetation (2007 to 2017) and to study its responses to a major drought in 2012. Orbital SIF data from the instrument GOME-2 was used along with MODIS MAIAC EVI and NDVI. Environmental data included precipitation rate (TRMM), surface temperature (MODIS) and soil moisture (ESA CCI). To support the interpretation of SIF responses we used red and far-red SIF adjusted by the Sun’s zenith angle (SIF-SZA) and by daily Photosynthetically Active Radiation (dSIF). Furthermore, we also adjusted SIF through two contrasting formulations using NDVI data as proxy for structure and biochemistry, based on previous leaf-level and landscape level studies: SIF-Yield and SIF-Prod. Data was tested with time-series decomposition, rank correlation, spatial correlation and Linear Mixed Models (LMM). Results show that GOME-2 SIF and adjusted SIF formulations responded consistently to the observed environmental variation and showed a marked decrease in SIF emissions in response to a 2012 drought that was generally larger than the corresponding NDVI and EVI decreases. Drought sensitivity of SIF, as inferred from LMM slopes, was correlated to land cover at different regions of the Caatinga. This is the first study to show correlation between landscape-level SIF and an emergent property of ecosystems (i.e., resilience), showcasing the value of remotely sensed fluorescence for ecological studies.

show abstract

Sun-Induced Fluorescence's Correlation to Carbon-Flux Increases When Raw Data is Adjusted to Account for Vegetation Biochemistry and Structure.

Cited by 2 publications

References 22 publications

Adjustments to SIF Aid the Interpretation of Drought Responses at the Caatinga of Northeast Brazil

Adjustments to SIF Aid the Interpretation of Drought Responses at the Caatinga of Northeast Brazil

Adjustments to SIF Aid the Interpretation of Drought Responses at the Caatinga of Northeast Brazil

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