A temperature-controlled spectrometer system for continuous and unattended measurements of canopy spectral radiance and reflectance

Drolet, Guillaume; Wade, Thomas J.; Nichol, Caroline; MacLellan, Christopher; Levula, Janne; Porcar‐Castell, Albert; Nikinmaa, Eero; Vesala, Timo

doi:10.1080/01431161.2014.882035

Cited by 33 publications

(40 citation statements)

References 28 publications

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“…However, local fluorescence measurement techniques are rapidly advancing and show their value in studying the ecophysiology of photosynthesis at the leaf level and in situ ( [52] and references therein). During the last decade, SiF has been successfully measured from tower [26,[64][65][66], aircraft [27,67,68] and satellite platforms [32,34,35,41]. For evaluation purposes, vegetation indices from satellite measurements (such as the NDVI) can be used as first proxies for SiF from spaceborne measurements due to their similar spatio-temporal patterns; they can therefore be used as a qualitative indicator of vegetation activity.…”

Section: Comparison With Ndvimentioning

confidence: 99%

Spaceborne Sun-Induced Vegetation Fluorescence Time Series from 2007 to 2015 Evaluated with Australian Flux Tower Measurements

et al. 2016

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Section: Comparison With Ndvimentioning

confidence: 99%

Spaceborne Sun-Induced Vegetation Fluorescence Time Series from 2007 to 2015 Evaluated with Australian Flux Tower Measurements

et al. 2016

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“…Most spectroradiometers are designed for periodic use, but continuous measurements and the validation of remote-sensing data are needed to improve PRI accuracy and application in assessing carbon uptake [137,138]. Regular calibration and the correction of data based on the effect of nonlinearity were therefore recommended to ensure data quality [85,137,139].…”

Section: Other Factorsmentioning

confidence: 99%

“…CHRIS/PROBA, however, can only provide a very limited spatial coverage, which inhibits the monitoring of multiple-angular PRI at regional and global scales [154]. A temperature-controlled spectrometric system was also designed to collect high resolution spectral data to detect the diurnal and seasonal variation of RUE and fluorescence [137]. Other instruments, such as a simple filtered photodiode (QuadPod) [155], a low-cost spectroscopic instrumentation (PRiAnalyze) [130] and an automated PRI sensor with upward-and downward-facing sensors [76], were developed to explore the environmental and physiological constraints on photosynthesis and to improve remote-sensing studies of carbon uptake.…”

Section: Instrumentsmentioning

confidence: 99%

Affecting Factors and Recent Improvements of the Photochemical Reflectance Index (PRI) for Remotely Sensing Foliar, Canopy and Ecosystemic Radiation-Use Efficiencies

et al. 2016

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Accurately assessing terrestrial gross primary productivity (GPP) is crucial for characterizing the climate-carbon cycle. Remotely sensing the photochemical reflectance index (PRI) across vegetation functional types and spatiotemporal scales has received increasing attention for monitoring photosynthetic performance and simulating GPP over the last two decades. The factors confounding PRI variation, especially on long timescales, however, require the improvement of PRI understanding to generalize its use for estimating carbon uptake. In this review, we summarize the most recent publications that have reported the factors affecting PRI variation across diurnal and seasonal scales at foliar, canopy and ecosystemic levels; synthesize the reported correlations between PRI and ecophysiological variables, particularly with radiation-use efficiency (RUE) and net carbon uptake; and analyze the improvements in PRI implementation. Long-term variation of PRI could be attributed to changes in the size of constitutive pigment pools instead of xanthophyll de-epoxidation, which controls the facultative short-term changes in PRI. Structural changes at canopy and ecosystemic levels can also affect PRI variation. Our review of the scientific literature on PRI suggests that PRI is a good proxy of photosynthetic efficiency at different spatial and temporal scales. Correcting PRI by decreasing the influence of physical or physiological factors on PRI greatly strengthens the relationships between PRI and RUE and GPP. Combining PRI with solar-induced fluorescence (SIF) and optical indices for green biomass offers additional prospects.

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“…While these instruments represent the "gold standard" for field reflectance measurements, many are bulky, expensive, and are not well suited to long-term, automated deployment in the field without additional modifications for unattended use (e.g., Hilker et al, 2007;Rossini et al, 2012;Drolet et al, 2014). Given the relationship between NDVI, PRI, and photosynthetic carbon uptake or NPP, there is a growing interest in monitoring these vegetation indices within the footprint of flux towers that measure the gas exchange of whole ecosystems.…”

Section: Introductionmentioning

confidence: 99%

Monitoring seasonal and diurnal changes in photosynthetic pigments with automated PRI and NDVI sensors

et al. 2015

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Abstract. The vegetation indices normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI) provide indicators of pigmentation and photosynthetic activity that can be used to model photosynthesis from remote sensing with the light-use-efficiency model. To help develop and validate this approach, reliable proximal NDVI and PRI sensors have been needed. We tested new NDVI and PRI sensors, "spectral reflectance sensors" (SRS sensors; recently developed by Decagon Devices, during spring activation of photosynthetic activity in evergreen and deciduous stands. We also evaluated two methods of sensor cross-calibration -one that considered sky conditions (cloud cover) at midday only, and another that also considered diurnal sun angle effects. Cross-calibration clearly affected sensor agreement with independent measurements, with the best method dependent upon the study aim and time frame (seasonal vs. diurnal). The seasonal patterns of NDVI and PRI differed for evergreen and deciduous species, demonstrating the complementary nature of these two indices. Over the spring season, PRI was most strongly influenced by changing chlorophyll : carotenoid pool sizes, while over the diurnal timescale, PRI was most affected by the xanthophyll cycle epoxidation state. This finding demonstrates that the SRS PRI sensors can resolve different processes affecting PRI over different timescales. The advent of small, inexpensive, automated PRI and NDVI sensors offers new ways to explore environmental and physiological constraints on photosynthesis, and may be particularly well suited for use at flux tower sites. Wider application of automated sensors could lead to improved integration of flux and remote sensing approaches for studying photosynthetic carbon uptake, and could help define the concept of contrasting vegetation optical types.

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A temperature-controlled spectrometer system for continuous and unattended measurements of canopy spectral radiance and reflectance

Cited by 33 publications

References 28 publications

Spaceborne Sun-Induced Vegetation Fluorescence Time Series from 2007 to 2015 Evaluated with Australian Flux Tower Measurements

Spaceborne Sun-Induced Vegetation Fluorescence Time Series from 2007 to 2015 Evaluated with Australian Flux Tower Measurements

Affecting Factors and Recent Improvements of the Photochemical Reflectance Index (PRI) for Remotely Sensing Foliar, Canopy and Ecosystemic Radiation-Use Efficiencies

Monitoring seasonal and diurnal changes in photosynthetic pigments with automated PRI and NDVI sensors

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