The 2013 FLEX—US Airborne Campaign at the Parker Tract Loblolly Pine Plantation in North Carolina, USA

Middleton, Elizabeth M.; Rascher, Uwe; Corp, Lawrence A.; Huemmrich, K. F.; Cook, Bruce D.; Noormets, Asko; Schickling, Anke; Pinto, Francisco; Alonso, Luis; Damm, Alexander; Guanter, Luis; Colombo, R.; Campbell, Petya K. E.; Landis, D.R.; Zhang, Qingyuan; Rossini, Micol; Schuettemeyer, Dirk; Bianchi, R.

doi:10.3390/rs9060612

Cited by 30 publications

(19 citation statements)

References 63 publications

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“…Similar relationships were also observed for both SIF A and SIF B in relation to CI red . These findings are corroborated by previous research evaluating the relationship of canopy PRI and a chlorophyll index (e.g., MTCI) for loblolly stands of various ages [30]. Our findings confirm the capability of SIF A , SIF B , SIF A+B , and their yields to enable more consistent interpretation and estimation of GPP and LUE, and strongly suggest that their diurnal and seasonal dynamics should be considered for scaling of photosynthetic function from leaf to canopy levels.…”

Section: Discussionsupporting

confidence: 90%

“…Remote sensing of SIF is a research field of growing interest, with potential to provide an improved tool for monitoring plant status and photosynthetic function. Developments in airborne and space-borne remote sensing have provided opportunities to observe local, regional, and global terrestrial SIF patterns, and have attracted a considerable amount of attention within the scientific community [28][29][30][31][32][33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

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Diurnal and Seasonal Variations in Chlorophyll Fluorescence Associated with Photosynthesis at Leaf and Canopy Scales

et al. 2019

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There is a critical need for sensitive remote sensing approaches to monitor the parameters governing photosynthesis, at the temporal scales relevant to their natural dynamics. The photochemical reflectance index (PRI) and chlorophyll fluorescence (F) offer a strong potential for monitoring photosynthesis at local, regional, and global scales, however the relationships between photosynthesis and solar induced F (SIF) on diurnal and seasonal scales are not fully understood. This study examines how the fine spatial and temporal scale SIF observations relate to leaf level chlorophyll fluorescence metrics (i.e., PSII yield, YII and electron transport rate, ETR), canopy gross primary productivity (GPP), and PRI. The results contribute to enhancing the understanding of how SIF can be used to monitor canopy photosynthesis. This effort captured the seasonal and diurnal variation in GPP, reflectance, F, and SIF in the O2A (SIFA) and O2B (SIFB) atmospheric bands for corn (Zea mays L.) at a study site in Greenbelt, MD. Positive linear relationships of SIF to canopy GPP and to leaf ETR were documented, corroborating published reports. Our findings demonstrate that canopy SIF metrics are able to capture the dynamics in photosynthesis at both leaf and canopy levels, and show that the relationship between GPP and SIF metrics differs depending on the light conditions (i.e., above or below saturation level for photosynthesis). The sum of SIFA and SIFB (SIFA+B), as well as the SIFA+B yield, captured the dynamics in GPP and light use efficiency, suggesting the importance of including SIFB in monitoring photosynthetic function. Further efforts are required to determine if these findings will scale successfully to airborne and satellite levels, and to document the effects of data uncertainties on the scaling.

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Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Diurnal and Seasonal Variations in Chlorophyll Fluorescence Associated with Photosynthesis at Leaf and Canopy Scales

et al. 2019

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“…The range of experiments presented is somewhat analogous to how different remote sensing platforms may observe canopies at shorter (diurnal) and longer timescales (seasonal). At the canopy scale, some studies have indicated that red:far‐red SIF can vary by over 50% during the course of a day, suggesting that this is a dynamic diurnal response of plants to environmental stress (Cheng et al, ; Middleton et al, ; Rossini et al, ; Wieneke et al, , ). Based on our leaf and canopy measurements, we consider that preferential quenching of PSII alone is unlikely to explain this variation, even for highly stressed leaves (Figures and ).…”

Section: Discussionmentioning

confidence: 99%

“…By accounting for changes in the spectral shape due to Chl reabsorption, researchers have suggested that the red:far-red ChlF ratio can potentially provide information on the responses of vegetation to water, temperature, or nitrogen stresses (Ač et al, 2015;Agati, 1998;Buschmann, 2007;Genty et al, 1990;Lichtenthaler et al, 1998). Building on this, some canopyscale research indicates that large diurnal changes in the remotely sensed red:far-red SIF ratio can be attributed to the downregulation of photosynthesis (Ač et al, 2015;Middleton et al, 2017;Wieneke et al, 2016Wieneke et al, , 2018; but note that this may be overshadowed by canopy structure and measurement geometry effects (Goulas et al, 2017;Liu et al, 2018). However, we are not aware of any attempts to disentangle contributing factors (i.e., Chl and changes in PSI/PSII fluorescence contributions), which simultaneously impact the spectral shape of ChlF ratio on single leaves.…”

Section: Introductionmentioning

confidence: 99%

Disentangling Changes in the Spectral Shape of Chlorophyll Fluorescence: Implications for Remote Sensing of Photosynthesis

et al. 2019

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Novel satellite measurements of solar‐induced chlorophyll fluorescence (SIF) can improve our understanding of global photosynthesis; however, little is known about how to interpret the controls on its spectral variability. To address this, we disentangle simultaneous drivers of fluorescence spectra by coupling active and passive fluorescence measurements with photosynthesis. We show empirical and mechanistic evidence for where, why, and to what extent leaf fluorescence spectra change. Three distinct components explain more than 95% of the variance in leaf fluorescence spectra under both steady‐state and changing illumination conditions. A single spectral shape of fluorescence explains 84% of the variance across a wide range of species. The magnitude of this shape responds to absorbed light and photosynthetic up/down regulation; meanwhile, chlorophyll concentration and nonphotochemical quenching control 9% and 3% of the remaining spectral variance, respectively. The spectral shape of fluorescence is remarkably stable where most current satellite retrievals occur (“far‐red,” >740nm), and dynamic downregulation of photosynthesis reduces fluorescence magnitude similarly across the 670‐ to 850‐nm range. We conduct an exploratory analysis of hourly red and far‐red canopy SIF in soybean, which shows a subtle change in red:far‐red fluorescence coincident with photosynthetic downregulation but is overshadowed by longer‐term changes in canopy chlorophyll and structure. Based on our leaf and canopy analysis, caution should be taken when attributing large changes in the spectral shape of remotely sensed SIF to plant stress, particularly if data acquisition is temporally sparse. Ultimately, changes in SIF magnitude at wavelengths greater than 740 nm alone may prove sufficient for tracking photosynthetic dynamics.

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“…This study was performed at the Parker Tract forest in the lower coastal plain near Plymouth, North Carolina, United States, in the context of the joint 2013 ESA/NASA FLEX airborne campaign (Middleton et al., ). The forest is a 4,400 ha managed plantation that contains various loblolly pine ( Pinus taeda L.) stands of different ages.…”

Section: Methodsmentioning

confidence: 99%

Variability of sun‐induced chlorophyll fluorescence according to stand age‐related processes in a managed loblolly pine forest

Colombo

Celesti

Bianchi

et al. 2018

Global Change Biology

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Leaf fluorescence can be used to track plant development and stress, and is considered the most direct measurement of photosynthetic activity available from remote sensing techniques. Red and far-red sun-induced chlorophyll fluorescence (SIF) maps were generated from high spatial resolution images collected with the HyPlant airborne spectrometer over even-aged loblolly pine plantations in North Carolina (United States). Canopy fluorescence yield (i.e., the fluorescence flux normalized by the light absorbed) in the red and far-red peaks was computed. This quantifies the fluorescence emission efficiencies that are more directly linked to canopy function compared to SIF radiances. Fluorescence fluxes and yields were investigated in relation to tree age to infer new insights on the potential of those measurements in better describing ecosystem processes. The results showed that red fluorescence yield varies with stand age. Young stands exhibited a nearly twofold higher red fluorescence yield than mature forest plantations, while the far-red fluorescence yield remained constant. We interpreted this finding in a context of photosynthetic stomatal limitation in aging loblolly pine stands. Current and future satellite missions provide global datasets of SIF at coarse spatial resolution, resulting in intrapixel mixture effects, which could be a confounding factor for fluorescence signal interpretation. To mitigate this effect, we propose a surrogate of the fluorescence yield, namely the Canopy Cover Fluorescence Index (CCFI) that accounts for the spatial variability in canopy structure by exploiting the vegetation fractional cover. It was found that spatial aggregation tended to mask the effective relationships, while the CCFI was still able to maintain this link. This study is a first attempt in interpreting the fluorescence variability in aging forest stands and it may open new perspectives in understanding long-term forest dynamics in response to future climatic conditions from remote sensing of SIF.

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The 2013 FLEX—US Airborne Campaign at the Parker Tract Loblolly Pine Plantation in North Carolina, USA

Cited by 30 publications

References 63 publications

Diurnal and Seasonal Variations in Chlorophyll Fluorescence Associated with Photosynthesis at Leaf and Canopy Scales

Diurnal and Seasonal Variations in Chlorophyll Fluorescence Associated with Photosynthesis at Leaf and Canopy Scales

Disentangling Changes in the Spectral Shape of Chlorophyll Fluorescence: Implications for Remote Sensing of Photosynthesis

Variability of sun‐induced chlorophyll fluorescence according to stand age‐related processes in a managed loblolly pine forest

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