Impact of varying irradiance on vegetation indices and chlorophyll fluorescence derived from spectroscopy data

Damm, Alexander; Guanter, Luis; Verhoef, W.; Schläpfer, Daniel; Garbari, Silvia; Schaepman, Michael E.

doi:10.1016/j.rse.2014.09.031

Cited by 105 publications

(93 citation statements)

References 67 publications

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“…In addition, the combination of forest structural variables and sun illumination causes specific patterns of cast shadow. These illumination effects often persist after atmospheric compensation, particularly for heterogeneous surfaces measured in high spatial resolution [119]. These processing artifacts eventually translate into optical indices derived and allow relating them with canopy structural variables as shown with our results.…”

Section: Reliability Of Structural Parameter Retrieval From Apex Datasupporting

confidence: 66%

Estimation of Alpine Forest Structural Variables from Imaging Spectrometer Data

et al. 2015

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Spatial information of forest structural variables is crucial for sustainable forest management planning, forest monitoring, and the assessment of forest ecosystem productivity. We investigate a complex alpine forest ecosystem located in the Swiss National Park (SNP) and apply empirical models to retrieve the structural variables canopy closure, basal area, and timber volume at plot scale. We used imaging spectrometer (IS) data from the Airborne Prism EXperiment (APEX) in combination with in-situ measurements of forest structural variables to develop empirical models. These models are based on simple and stepwise multiple regressions, while all potential two narrow-band combinations of the Simple Ratio (SR), the Normalized Difference Vegetation Index (NDVI), the perpendicular vegetation index (PVI), the second soil-adjusted vegetation index (SAVI2), and band depth indices were tested. The accuracy of the estimated structural attributes was evaluated using a leave-one-out cross-validation technique. Using stepwise multiple regression models, we obtained a moderate to good accuracy when estimating canopy closure (R 2 = 0.81, rRMSE = 10%), basal area (R 2 = 0.68, rRMSE = 20%), and timber volume (R 2 = 0.73, rRMSE = 22%). We discuss the reliability of empirical approaches for estimates of canopy structural parameters considering the causality of light interaction and surface information.

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Section: Reliability Of Structural Parameter Retrieval From Apex Datasupporting

confidence: 66%

Estimation of Alpine Forest Structural Variables from Imaging Spectrometer Data

et al. 2015

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“…Inasmuch as PRI of natural canopies is particularly sensitive to directional irradiance [64], our results suggest that shifts in carotenoid contents are responsible for the variation in the PRI-LUE relationship when PRI is measured at viewing angles close to the nadir in the field [16]. A similar mechanism can be responsible for increased PRI-LUE correlations for observations from satellites at higher viewing angles from the zenith [65].…”

Section: Use Of Pri For Determining Photosynthetic Parametersmentioning

confidence: 63%

Potential of Photochemical Reflectance Index for Indicating Photochemistry and Light Use Efficiency in Leaves of European Beech and Norway Spruce Trees

et al. 2018

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Hyperspectral reflectance is becoming more frequently used for measuring the functions and productivity of ecosystems. The purpose of this study was to re-evaluate the potential of the photochemical reflectance index (PRI) for evaluating physiological status of plants. This is needed because the reasons for variation in PRI and its relationships to physiological traits remain poorly understood. We examined the relationships between PRI and photosynthetic parameters in evergreen Norway spruce and deciduous European beech grown in controlled conditions during several consecutive periods of 10-12 days between which the irradiance and air temperature were changed stepwise. These regime changes induced significant changes in foliar biochemistry and physiology. The responses of PRI corresponded particularly to alterations in the actual quantum yield of photosystem II photochemistry (Φ PSII ). Acclimation responses of both species led to loss of PRI sensitivity to light use efficiency (LUE). The procedure of measuring PRI at multiple irradiance-temperature conditions has been designed also for testing accuracy of ∆PRI in estimating LUE. A correction mechanism of subtracting daily measured PRI from early morning PRI has been performed to account for differences in photosynthetic pigments between irradiance-temperature regimes. Introducing ∆PRI, which provided a better estimate of non-photochemical quenching (NPQ) compared to PRI, also improved the accuracy of LUE estimation. Furthermore, ∆PRI was able to detect the effect of drought, which is poorly observable from PRI.

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“…The importance and success of the red fluorescence variables, as compared to the far-red fluorescence, is supported by several published radiative transfer modeling efforts and current state-of-the-art fluorescence models [57][58][59][60][61][62]. These papers demonstrate that the red fluorescence is more sensitive to vegetation physiological variables than the far-red fluorescence and is potentially retrievable from satellite orbit [63].…”

Section: Far-red Vs Red Fluorescence Radiancesmentioning

confidence: 91%

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

Middleton¹,

Rascher

Corp

et al. 2017

Remote Sensing

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Abstract:The first European Space Agency (ESA) and NASA collaboration in an airborne campaign to support ESA's FLuorescence EXplorer (FLEX) mission was conducted in North Carolina, USA during September-October 2013 (FLEX-US 2013) at the Parker Tract Loblolly Pine (LP) Plantation (Plymouth, NC, USA). This campaign combined two unique airborne instrument packages to obtain simultaneous observations of solar-induced fluorescence (SIF), LiDAR-based canopy structural information, visible through shortwave infrared (VSWIR) reflectance spectra, and surface temperature, to advance vegetation studies of carbon cycle dynamics and ecosystem health. We obtained statistically significant results for fluorescence, canopy temperature, and tower fluxes from data collected at four times of day over two consecutive autumn days across an age class chronosequence. Both the red fluorescence (F685) and far-red fluorescence (F740) radiances had highest values at mid-day, but their fluorescence yields exhibited different diurnal responses across LP age classes. The diurnal trends for F685 varied with forest canopy temperature difference (canopy minus air), having a stronger daily amplitude change for young vs. old canopies. The Photochemical Reflectance Index (PRI) was positively correlated with this temperature variable over the diurnal cycle. Tower measurements from mature loblolly stand showed the red/far-red fluorescence ratio was linearly related to canopy light use efficiency (LUE) over the diurnal cycle, but performed even better Remote Sens. 2017, 9, 612; doi:10.3390/rs9060612www.mdpi.com/journal/remotesensing Remote Sens. 2017, 9, 612 2 of 31 for the combined morning/afternoon (without midday) observations. This study demonstrates the importance of diurnal observations for interpretation of fluorescence dynamics, the need for red fluorescence to understand canopy physiological processes, and the benefits of combining fluorescence, reflectance, and structure information to clarify canopy function versus structure characteristics for a coniferous forest.

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Impact of varying irradiance on vegetation indices and chlorophyll fluorescence derived from spectroscopy data

Cited by 105 publications

References 67 publications

Estimation of Alpine Forest Structural Variables from Imaging Spectrometer Data

Estimation of Alpine Forest Structural Variables from Imaging Spectrometer Data

Potential of Photochemical Reflectance Index for Indicating Photochemistry and Light Use Efficiency in Leaves of European Beech and Norway Spruce Trees

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

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