scholarly journals Diurnal and Seasonal Solar Induced Chlorophyll Fluorescence and Photosynthesis in a Boreal Scots Pine Canopy

2019 ◽  
Vol 11 (3) ◽  
pp. 273 ◽  
Author(s):  
Caroline Nichol ◽  
Guillaume Drolet ◽  
Albert Porcar-Castell ◽  
Tom Wade ◽  
Neus Sabater ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Eddy Covariance ◽  
Scots Pine ◽  
Optical System ◽  
Spatial Scales ◽  
Gross Primary Production ◽  
Photochemical Efficiency ◽  
Effective Quantum Yield ◽  
Time Step ◽  
Eddy Covariance System

Solar induced chlorophyll fluorescence has been shown to be increasingly an useful proxy for the estimation of gross primary productivity (GPP), at a range of spatial scales. Here, we explore the seasonality in a continuous time series of canopy solar induced fluorescence (hereafter SiF) and its relation to canopy gross primary production (GPP), canopy light use efficiency (LUE), and direct estimates of leaf level photochemical efficiency in an evergreen canopy. SiF was calculated using infilling in two bands from the incoming and reflected radiance using a pair of Ocean Optics USB2000+ spectrometers operated in a dual field of view mode, sampling at a 30 min time step using custom written automated software, from early spring through until autumn in 2011. The optical system was mounted on a tower of 18 m height adjacent to an eddy covariance system, to observe a boreal forest ecosystem dominated by Scots pine. (Pinus sylvestris) A Walz MONITORING-PAM, multi fluorimeter system, was simultaneously mounted within the canopy adjacent to the footprint sampled by the optical system. Following correction of the SiF data for O2 and structural effects, SiF, SiF yield, LUE, the photochemicsl reflectance index (PRI), and the normalized difference vegetation index (NDVI) exhibited a seasonal pattern that followed GPP sampled by the eddy covariance system. Due to the complexities of solar azimuth and zenith angle (SZA) over the season on the SiF signal, correlations between SiF, SiF yield, GPP, and LUE were assessed on SZA <50° and under strictly clear sky conditions. Correlations found, even under these screened scenarios, resulted around ~r2 = 0.3. The diurnal responses of SiF, SiF yield, PAM estimates of effective quantum yield (ΔF/Fm′), and meteorological parameters demonstrated some agreement over the diurnal cycle. The challenges inherent in SiF retrievals in boreal evergreen ecosystems are discussed.

scholarly journals Design of the AmeriFlux Portable Eddy Covariance System and Uncertainty Analysis of Carbon Measurements

2007 ◽  
Vol 24 (8) ◽  
pp. 1389-1406 ◽  
Author(s):  
T. W. Ocheltree ◽  
H. W. Loescher
Keyword(s):  
Eddy Covariance ◽  
Spatial Scales ◽  
Flux Measurement ◽  
Field Measurements ◽  
Quality Control Laboratory ◽  
Flux Measurements ◽  
Eddy Covariance System ◽  
Uncertainty Analyses ◽  
Infrared Gas Analyzer ◽  
Ambient Co2

Abstract The AmeriFlux network continues to improve the understanding of carbon, water, and energy fluxes across temporal and spatial scales. The network includes ∼120 research sites that contribute to the understanding of processes within and among ecosystems. To improve the networks ability and confidence to synthesize data across multiple sites, the AmeriFlux quality assurance and quality control laboratory was established to reduce the within- and among-site uncertainties. This paper outlines the design of the portable eddy covariance system (PECS) and subsequent data processing procedures used for site comparisons. Because the PECS makes precision measurements of atmospheric CO2, the authors also present the results of uncertainty analyses in determining the polynomials for an infrared gas analyzer, estimating the CO2 in secondary standards, and estimating ambient CO2 in field measurements. Under field conditions, drift in the measurement of CO2 increased the uncertainty in flux measurements across 7 days by 5% and was not dependent on the magnitude or direction of the flux. The maximum relative flux measurement error for unstable conditions was 10.03 μmol CO2 m−2 s−1.

Calibration and validation of a simplified process-based model for the prediction of the carbon balance of Scottish Sitka spruce (Picea sitchensis) plantations

2010 ◽  
Vol 40 (12) ◽  
pp. 2411-2426 ◽  
Author(s):  
Francesco Minunno ◽  
Georgios Xenakis ◽  
Michael P. Perks ◽  
Maurizio Mencuccini
Keyword(s):  
Carbon Sequestration ◽  
Eddy Covariance ◽  
Carbon Balance ◽  
Growth Models ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Sitka Spruce ◽  
Picea Sitchensis ◽  
Forest Growth ◽  
Time Step

There is increasing recognition that forestry provides a low cost and robust means of climate change abatement through carbon sequestration and substitution. However, current understanding of forest ecosystem carbon exchange and forest–atmosphere interactions are often inadequately characterized by existing empirical growth models with resulting poor representation for regional extrapolations. In this paper, we describe the parameterisation and independent validation, against both eddy covariance and forest growth experimental data, of a process-oriented model 3PGN to provide assessments of carbon sequestration of Sitka spruce (Picea sitchensis (Bong.) Carrière) plantations across Scotland. In comparison with eddy covariance measurements, the model predicted all of the major annual carbon fluxes, i.e., gross primary production (PG), net ecosystem production (PE), and ecosystem respiration (RE), with biases lower than 10%. At a monthly time step, only PG and PE were accurately estimated, whereas RE was not. At longer time scales (i.e., several decades), the model reliably represented the major patterns of the carbon balance. Soil type was identified as the important factor influencing site productivity; fertilization practices did not alter long-term site nutritional status. The analyses also highlighted the potential impact of carbon loss from carbon-rich soils, which can result in differences between optimal rotation length for carbon sequestration and for timber production.

scholarly journals Mapping Photosynthesis Solely from Solar-Induced Chlorophyll Fluorescence: A Global, Fine-Resolution Dataset of Gross Primary Production Derived from OCO-2

2019 ◽  
Vol 11 (21) ◽  
pp. 2563 ◽  
Author(s):  
Li ◽  
Xiao
Keyword(s):  
Chlorophyll Fluorescence ◽  
Primary Production ◽  
Gross Primary Production ◽  
Grid Cell ◽  
Data Repository ◽  
Climate Data ◽  
Time Step ◽  
Coarse Resolution ◽  
Median Estimate ◽  
Fine Resolution

Accurately quantifying gross primary production (GPP) globally is critical for assessing plant productivity, carbon balance, and carbon-climate feedbacks, while current GPP estimates exhibit substantial uncertainty. Solar-induced chlorophyll fluorescence (SIF) observed by the Orbiting Carbon Observatory-2 (OCO-2) has offered unprecedented opportunities for monitoring land photosynthesis, while its sparse coverage remains a bottleneck for mapping finer-resolution GPP globally. Here, we used the global, OCO-2-based SIF product (GOSIF) and linear relationships between SIF and GPP to map GPP globally at a 0.05° spatial resolution and 8-day time step for the period from 2000 to 2017. To account for the uncertainty of GPP estimates resulting from the SIF-GPP relationship, we used a total of eight SIF-GPP relationships with different forms (universal and biome-specific, with and without intercept) at both site and grid cell levels to estimate GPP. Our results showed that all of the eight SIF-GPP relationships performed well in estimating GPP globally. The ensemble mean 8-day GPP was generally highly correlated with flux tower GPP for 91 eddy covariance flux sites across the globe (R2 = 0.74, Root Mean Square Error = 1.92 g C m−2 d−1). Our fine-resolution GPP estimates showed reasonable spatial and seasonal variations across the globe and fully captured both seasonal cycles and spatial patterns present in our coarse-resolution (1°) GPP estimates based on coarse-resolution SIF data directly aggregated from discrete OCO-2 soundings. SIF-GPP relationships with different forms could lead to significant differences in annual GPP particularly in the tropics. Our ensemble global annual GPP estimate (135.5 ± 8.8 Pg C yr−1) is between the median estimate of non-process based methods and the median estimate of process-based models. Our GPP estimates showed interannual variability in many regions and exhibited increasing trends in many parts of the globe particularly in the Northern Hemisphere. With the availability of high-quality, gridded SIF observations from space (e.g., TROPOMI, FLEX), our novel approach does not rely on any other input data (e.g., climate data, soil properties) and therefore can map GPP solely based on satellite SIF observations and potentially lead to more accurate GPP estimates at regional to global scales. The use of a universal SIF-GPP relationship versus biome-specific relationships can also avoid the uncertainty associated with land cover maps. Our novel, independent GPP product (GOSIF GPP), freely available at our data repository, will be valuable for studying photosynthesis, carbon cycle, agricultural production, and ecosystem responses to climate change and disturbances, informing ecosystem management, and benchmarking terrestrial biosphere and Earth system models.

scholarly journals Potential of chlorophyll fluorescence and VIS/NIR spectroscopy measurement use for the detection of nitrogen content and disease infection of apple leaves

2011 ◽  
Vol 59 (6) ◽  
pp. 317-328 ◽  
Author(s):  
Václava Spáčilová ◽  
Ivana Šafránková
Keyword(s):  
Chlorophyll Fluorescence ◽  
Nitrogen Content ◽  
Fungal Pathogens ◽  
Venturia Inaequalis ◽  
Vegetation Indices ◽  
Photochemical Efficiency ◽  
Correlation Coefficients ◽  
Nir Spectroscopy ◽  
Effective Quantum Yield ◽  
Significant Difference

A possibility of using spectral methods for determining a nutritional status and detecting pathogens in apple-tree cvs. ’Jonagold’ and ’Idared’ was verified in an orchard and pot experiments in 2007–2010. Treatments differed in the fertilizer or fungicide dose. Leaf samples were collected from the experimental variants to determine nitrogen content and to measure spectral reflectance (spectrophotometer Avantes USB 2000) and chlorophyll fluorescence imaging (FluorCam). Results of the measurements were correlated to leaf analyses for nitrogen content in dry matter. At the same time, a health status (the occurrence of fungal pathogens Venturia inaequalis and Podosphaera leucotricha) was assessed and changes of photochemical efficiency of PSII of infected leaves were evaluated. The parameters providing the best description of differences in the photosynthetic activity of leaves depending on treatments (parameter Fv/Fm and parameter GENTY, known as ΦPSII – effective quantum yield of PSII) were selected. The values of correlation coefficients of Fv/Fm and ΦPSII depending on fertilization treatments were as follows: Fv/Fm: r = −0.4735, p<0.000089, α = 0.05; ΦPSII: r = 0.755; p < 0.00038, α = 0.05. Data obtained from measuring with a spectrophotometer was used for the calculation to normalized difference vegetation indices NDVI; a significant relationship was found for the index GNDVI (r = 0.4691, p < 0,0002, α = 0.05). The significant difference between healthy leaves and leaves infected by the pathogens V. inaequalis and P. leucotricha was confirmed using the spectrophotometer, and the largest differences in reflectances were found in wavelengths around 400 nm. The values of indices GNDVI, RNDVI and NDVI 450 obtained from measuring reflectance of leaves with symptoms of V. inaequalis and P. leucotricha infections were significantly lower compared to the indices of healthy leaves. The values of indices NDVI were as follows: GNDVI 0.930; RNDVI 0.912; NDVI 450 0.917 for healthy leaves and GNDVI 0.519/0.623; RNDVI 0.428/0.540; NDVI 450 0.432/0.499 for leaves infected by pathogens V. inaequalis/P. leucotricha, respectively. There was found significant difference between infected and healthy leaves for all indices (α = 0.05). Also, the ΦPSII exhibited significant responses to the presence of V. inaequalis and P. leucotricha (ΦPSII: healthy leaves 0.182; V. inaequalis/P. leucotricha presence 0.232/0.222; α = 0.05).

scholarly journals Upscaling Solar-Induced Chlorophyll Fluorescence from an Instantaneous to Daily Scale Gives an Improved Estimation of the Gross Primary Productivity

2018 ◽  
Vol 10 (10) ◽  
pp. 1663 ◽  
Author(s):  
Jiaochan Hu ◽  
Liangyun Liu ◽  
Jian Guo ◽  
Shanshan Du ◽  
Xinjie Liu
Keyword(s):  
Chlorophyll Fluorescence ◽  
Spatial Scales ◽  
Gross Primary Production ◽  
Weather Conditions ◽  
Coefficient Of Determination ◽  
Atmospheric Scattering ◽  
Daily Scale ◽  
Weather Changes ◽  
Length Of The Day

Solar-induced chlorophyll fluorescence (SIF) is closely linked to the photosynthesis of plants and has the potential to estimate gross primary production (GPP) at different temporal and spatial scales. However, remotely sensed SIF at a ground or space level is usually instantaneous, which cannot represent the daily total SIF. The temporal mismatch between instantaneous SIF (SIFinst) and daily GPP (GPPdaily) impacts their correlation across space and time. Previous studies have upscaled SIFinst to the daily scale based on the diurnal cycle in the cosine of the solar zenith angle ( cos ( SZA ) ) to correct the effects of latitude and length of the day on the variations in the SIF-GPP correlation. However, the important effects of diurnal weather changes due to cloud and atmospheric scattering were not considered. In this study, we present a SIF upscaling method using photosynthetically active radiation (PAR) as a driving variable. First, a conversion factor (i.e., the ratio of the instantaneous PAR (PARinst) to daily PAR (PARdaily)) was used to upscale in-situ SIF measurements from the instantaneous to daily scale. Then, the performance of the SIF upscaling method was evaluated under changing weather conditions and different latitudes using continuous tower-based measurements at two sites. The results prove that our PAR-based method can reduce not only latitude-dependent but also the weather-dependent variations in the SIF-GPP model. Specifically, the PAR-based method gave a more accurate prediction of diurnal and daily SIF (SIFdaily) than the cos ( SZA ) -based method, with decreased relative root mean square error (RRMSE) values from 42.2% to 25.6% at half-hour intervals and from 25.4% to 13.3% at daily intervals. Moreover, the PAR-based upscaled SIFdaily had a stronger correlation with the daily absorbed PAR (APAR) than both the SIFinst and cos ( SZA ) -based upscaled SIFdaily, especially for cloudy days with a coefficient of determination (R2) that increased from approximately 0.5 to 0.8. Finally, the PAR-based SIFdaily was linked to GPPdaily and compared to the SIFinst or cos ( SZA ) -based SIFdaily. The results indicate that the SIF-GPP correlation can obviously be improved, with an increased R2 from approximately 0.65 to 0.75. Our study confirms the importance of upscaling SIF from the instantaneous to daily scale when linking SIF with GPP and emphasizes the need to take diurnal weather changes into account for SIF temporal upscaling.

scholarly journals Linking remote sensing parameters to CO2 assimilation rates at a leaf scale

2021 ◽  
Author(s):  
Kouki Hikosaka ◽  
Katsuto Tsujimoto
Keyword(s):  
Remote Sensing ◽  
Chlorophyll Fluorescence ◽  
Heat Dissipation ◽  
Spatial Scales ◽  
Photochemical Efficiency ◽  
Co2 Assimilation ◽  
Photochemical Quenching ◽  
Future Prediction ◽  
Environmental Responses ◽  
Non Photochemical Quenching

AbstractSolar-induced chlorophyll fluorescence (SIF) and photochemical reflectance index (PRI) are expected to be useful for remote sensing of photosynthetic activity at various spatial scales. This review discusses how chlorophyll fluorescence and PRI are related to the CO2 assimilation rate at a leaf scale. Light energy absorbed by photosystem II chlorophylls is allocated to photochemistry, fluorescence, and heat dissipation evaluated as non-photochemical quenching (NPQ). PRI is correlated with NPQ because it reflects the composition of xanthophylls, which are involved in heat dissipation. Assuming that NPQ is uniquely related to the photochemical efficiency (quantum yield of photochemistry), photochemical efficiencies can be assessed from either chlorophyll fluorescence or PRI. However, this assumption may not be held under some conditions such as low temperatures and photoinhibitory environments. Even in such cases, photosynthesis may be estimated more accurately if both chlorophyll fluorescence and PRI are determined simultaneously. To convert from photochemical efficiency to CO2 assimilation, environmental responses in stomatal conductance also need to be considered. Models linking chlorophyll fluorescence and PRI with CO2 assimilation rates will contribute to understanding and future prediction of the global carbon cycle.

scholarly journals Energy balance measurements over a banana orchard in the Semiarid region in the Northeast of Brazil

2009 ◽  
Vol 44 (11) ◽  
pp. 1365-1373 ◽  
Author(s):  
Carlos Antonio Costa dos Santos ◽  
Bernardo Barbosa da Silva ◽  
Tantravahi Venkata Ramana Rao ◽  
Christopher Michael Usher Neale
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Heat Fluxes ◽  
Irrigation District ◽  
Semiarid Region ◽  
Energy Balance Closure ◽  
Wet Season ◽  
Growing Seasons ◽  
Eddy Covariance System

The objective of this work was to evaluate the reliability of eddy covariance measurements, analyzing the energy balance components, evapotranspiration and energy balance closure in dry and wet growing seasons, in a banana orchard. The experiment was carried out at a farm located within the irrigation district of Quixeré, in the Lower Jaguaribe basin, in Ceará state, Brazil. An eddy covariance system was used to measure the turbulent flux. An automatic weather station was installed in a grass field to obtain the reference evapotranspiration (ET0) from the combined FAO-Penman-Monteith method. Wind speed and vapor pressure deficit are the most important variables on the evaporative process in both growing seasons. In the dry season, the heat fluxes have a similar order of magnitude, and during the wet season the latent heat flux is the largest. The eddy covariance system had acceptable reliability in measuring heat flux, with actual evapotranspiration results comparing well with those obtained by using the water balance method. The energy balance closure had good results for the study area, with mean values of 0.93 and 0.86 for the dry and wet growing seasons respectively.

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