Comparative Analysis on the Estimation of Diurnal Solar-Induced Chlorophyll Fluorescence Dynamics for a Subtropical Evergreen Coniferous Forest

Solar-induced chlorophyll fluorescence (SIF) is considered as a prospective indicator of vegetation photosynthetic activity and the ecosystem carbon cycle. The current coarse spatial-temporal resolutions of SIF data from satellite missions and ground measurements still cannot satisfy the corroboration of its correlation with photosynthesis and carbon flux. Practical approaches are needed to be explored for the supplementation of the SIF measurements. In our study, we clarified the diurnal variations of leaf and canopy chlorophyll fluorescence for a subtropical evergreen coniferous forest and evaluated the performance of the canopy chlorophyll concentration (CCC) approach and the backward approach from gross primary production (GPP) for estimating the diurnal variations of canopy SIF by comparing with the Soil Canopy Observation Photosynthesis Energy (SCOPE) model. The results showed that the canopy SIF had similar seasonal and diurnal variations with the incident photosynthetically active radiation (PAR) above the canopy, while the leaf steady-state fluorescence remained stable during the daytime. Neither the CCC nor the raw backward approach from GPP could capture the short temporal dynamics of canopy SIF. However, after improving the backward approach with a correction factor of normalized PAR incident on leaves, the variation of the estimated canopy SIF accounted for more than half of the diurnal variations in the canopy SIF (SIF687: R2 = 0.53, p < 0.001; SIF760: R2 = 0.72, p < 0.001) for the subtropical evergreen coniferous forest without water stress. Drought interfered with the utilization of the improved backward approach because of the decoupling of SIF and GPP due to stomatal closure. This new approach offers new insight into the estimation of diurnal canopy SIF and can help understand the photosynthesis of vegetation for future climate change studies.

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Modelling sun-induced fluorescence and photosynthesis with a land surface model at local and regional scales in northern Europe

Biogeosciences ◽

10.5194/bg-14-1969-2017 ◽

2017 ◽

Vol 14 (7) ◽

pp. 1969-1987 ◽

Cited By ~ 23

Author(s):

Tea Thum ◽

Sönke Zaehle ◽

Philipp Köhler ◽

Tuula Aalto ◽

Mika Aurela ◽

...

Keyword(s):

Chlorophyll Fluorescence ◽

Land Surface ◽

Large Scale ◽

Model Simulation ◽

Gross Primary Production ◽

Regional Scale ◽

Coniferous Forest ◽

Flux Measurement ◽

Surface Model ◽

Fluorescence Measurements

Abstract. Recent satellite observations of sun-induced chlorophyll fluorescence (SIF) are thought to provide a large-scale proxy for gross primary production (GPP), thus providing a new way to assess the performance of land surface models (LSMs). In this study, we assessed how well SIF is able to predict GPP in the Fenno-Scandinavian region and what potential limitations for its application exist. We implemented a SIF model into the JSBACH LSM and used active leaf-level chlorophyll fluorescence measurements (Chl F) to evaluate the performance of the SIF module at a coniferous forest at Hyytiälä, Finland. We also compared simulated GPP and SIF at four Finnish micrometeorological flux measurement sites to observed GPP as well as to satellite-observed SIF. Finally, we conducted a regional model simulation for the Fenno-Scandinavian region with JSBACH and compared the results to SIF retrievals from the GOME-2 (Global Ozone Monitoring Experiment-2) space-borne spectrometer and to observation-based regional GPP estimates. Both observations and simulations revealed that SIF can be used to estimate GPP at both site and regional scales. At regional scale the model was able to simulate observed SIF averaged over 5 years with r2 of 0.86. The GOME-2-based SIF was a better proxy for GPP than the remotely sensed fAPAR (fraction of absorbed photosynthetic active radiation by vegetation). The observed SIF captured the seasonality of the photosynthesis at site scale and showed feasibility for use in improving of model seasonality at site and regional scale.

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Feasibility of Using MODIS Products to Simulate Sun-Induced Chlorophyll Fluorescence (SIF) in Boreal Forests

Remote Sensing ◽

10.3390/rs12040680 ◽

2020 ◽

Vol 12 (4) ◽

pp. 680 ◽

Cited By ~ 1

Author(s):

Meng Guo ◽

Jing Li ◽

Shubo Huang ◽

Lixiang Wen

Keyword(s):

Chlorophyll Fluorescence ◽

Boreal Forest ◽

Spatial Resolution ◽

Vegetation Index ◽

Mean Squared Error ◽

Gross Primary Production ◽

Coniferous Forest ◽

Terrestrial Ecosystems ◽

Linear Regression Models ◽

Modis Evi

Solar-induced chlorophyll fluorescence (SIF) is a novel approach to gain information about plant activity from remote sensing observations. However, there are currently no continuous SIF data produced at high spatial resolutions. Many previous studies have discussed the relationship between SIF and gross primary production (GPP) and showed a significant correlation between them, but few researchers have focused on forests, which are one the most important terrestrial ecosystems. This study takes Greater Khingan Mountains, a typical boreal forest in China, as an example to explore the feasibility of using MODerate resolution Imaging Spectroradiometer (MODIS) products and Orbiting Carbon Observatory-2 (OCO-2) SIF data to simulate continuous SIF at higher spatial resolutions. The results show that there is no significant correlation between SIF and MODIS GPP at a spatial resolution of 1 km; however, significant correlations between SIF and the enhanced vegetation index (EVI) were found during growing seasons. Furthermore, the broadleaf forest has a higher SIF than coniferous forest because of the difference in leaf and canopy bio-chemical and structural characteristic. When using MODIS EVI to model SIF, linear regression models show average performance (R2 = 0.58, Root Mean Squared Error (RMSE) = 0.14 from Julian day 145 to 257) at a 16-day time scale. However, when using MODIS EVI and temperature, multiple regressions perform better (R2 = 0.71, RMSE = 0.13 from Julian day 145 to 241). An important contribution of this paper is the analysis of the relationships between SIF and vegetation indices at different spatial resolutions and the finding that the relationships became closer with a decrease in spatial resolution. From this research, we conclude that the SIF of the boreal forest investigated can mainly be explained by EVI and air temperature.

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Continuous CO2/CH4/CO measurements (2012-2014) at Beromünster tall tower station in Switzerland

10.5194/bg-2015-593 ◽

2016 ◽

Cited By ~ 1

Author(s):

E. Satar ◽

T. A. Berhanu ◽

D. Brunner ◽

S. Henne ◽

M. Leuenberger

Keyword(s):

Regional Scale ◽

Vertical Mixing ◽

Monitoring Network ◽

Ground Level ◽

Diurnal Variations ◽

Future Climate Change ◽

Mixing Ratios ◽

Seasonal And Diurnal Variations ◽

Flux Measurements ◽

Storage Flux

Abstract. The understanding of the continental carbon budget is essential to predict future climate change. In order to quantify CO2 and CH4 fluxes at the regional scale, a measurement system was installed at the former radio tower in Beromünster as a part of the Swiss greenhouse gas monitoring network (CarboCount CH). We have been measuring the mixing ratios of CO2, CH4 and CO on this tower with sample inlets at 12.5, 44.6, 71.5, 131.6 and 212.5 m above ground level using a cavity ring down spectroscopy (CRDS) analyzer. The first two-year (December 2012-December 2014) continuous atmospheric record was analyzed for seasonal and diurnal variations and inter-species correlations. In addition, storage fluxes were calculated from the hourly profiles along the tower. The atmospheric growth rates from 2013 to 2014 determined from this two-year dataset were 1.78 ppm yr-1, 9.66 ppb yr-1 and -1.27 ppb yr-1 for CO2, CH4 and CO, respectively. After detrending, clear seasonal cycles were detected for CO2 and CO, whereas CH4 showed a stable baseline suggesting a net balance between sources and sinks over the course of the year. CO and CO2 were strongly correlated (r2 > 0.75) in winter (DJF), but almost uncorrelated in summer. In winter, anthropogenic emissions dominate the biospheric CO2 fluxes and the variations in mixing ratios are large due to reduced vertical mixing. The diurnal variations of all species showed distinct cycles in spring and summer, with the lo west sampling level showing the most pronounced diurnal amplitudes. The storage flux estimates exhibited reasonable diurnal shapes for CO2, but underestimated the strength of the surface sinks during daytime. This seems plausible, keeping in mind that we were only able to calculate the storage fluxes along the profile of the tower but not the flux into or out of this profile, since no Eddy covariance flux measurements were taken at the top of the tower.

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Continuous CO2/CH4/CO measurements (2012–2014) at Beromünster tall tower station in Switzerland

Biogeosciences ◽

10.5194/bg-13-2623-2016 ◽

2016 ◽

Vol 13 (9) ◽

pp. 2623-2635 ◽

Cited By ~ 16

Author(s):

Ece Satar ◽

Tesfaye A. Berhanu ◽

Dominik Brunner ◽

Stephan Henne ◽

Markus Leuenberger

Keyword(s):

Regional Scale ◽

Vertical Mixing ◽

Monitoring Network ◽

Ground Level ◽

Diurnal Variations ◽

Future Climate Change ◽

Data Set ◽

Mixing Ratios ◽

Seasonal And Diurnal Variations ◽

Storage Flux

Abstract. The understanding of the continental carbon budget is essential to predict future climate change. In order to quantify CO2 and CH4 fluxes at the regional scale, a measurement system was installed at the former radio tower in Beromünster as part of the Swiss greenhouse gas monitoring network (CarboCount CH). We have been measuring the mixing ratios of CO2, CH4 and CO on this tower with sample inlets at 12.5, 44.6, 71.5, 131.6 and 212.5 m above ground level using a cavity ring down spectroscopy (CRDS) analyzer. The first 2-year (December 2012–December 2014) continuous atmospheric record was analyzed for seasonal and diurnal variations and inter-species correlations. In addition, storage fluxes were calculated from the hourly profiles along the tower. The atmospheric growth rates from 2013 to 2014 determined from this 2-year data set were 1.78 ppm yr−1, 9.66 ppb yr−1 and −1.27 ppb yr−1 for CO2, CH4 and CO, respectively. After detrending, clear seasonal cycles were detected for CO2 and CO, whereas CH4 showed a stable baseline suggesting a net balance between sources and sinks over the course of the year. CO and CO2 were strongly correlated (r2 > 0.75) in winter (DJF), but almost uncorrelated in summer. In winter, anthropogenic emissions dominate the biospheric CO2 fluxes and the variations in mixing ratios are large due to reduced vertical mixing. The diurnal variations of all species showed distinct cycles in spring and summer, with the lowest sampling level showing the most pronounced diurnal amplitudes. The storage flux estimates exhibited reasonable diurnal shapes for CO2, but underestimated the strength of the surface sinks during daytime. This seems plausible, keeping in mind that we were only able to calculate the storage fluxes along the profile of the tower but not the flux into or out of this profile, since no Eddy covariance flux measurements were taken at the top of the tower.

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Modelling sun-induced fluorescence and photosynthesis with a land surface model at local and regional scales in northern Europe

10.5194/bg-2016-514 ◽

2016 ◽

Author(s):

Tea Thum ◽

Sönke Zaehle ◽

Philipp Köhler ◽

Tuula Aalto ◽

Mika Aurela ◽

...

Keyword(s):

Chlorophyll Fluorescence ◽

Land Surface ◽

Large Scale ◽

Model Simulation ◽

Gross Primary Production ◽

Coniferous Forest ◽

Land Surface Model ◽

Flux Measurement ◽

Surface Model ◽

Fluorescence Measurements

Abstract. Recent satellite observations of sun-induced chlorophyll fluorescence (SIF) are thought to provide a large-scale proxy for gross primary production (GPP), thus providing a new way to assess the performance of land surface models (LSMs). In this study, we assessed how well SIF is able to predict GPP in the Fenno-Scandinavian region and what potential limitations for its application exist. We implemented a SIF model into the JSBACH LSM and used active leaf level chlorophyll fluorescence measurements (ChlF) to evaluate the performance of the SIF module at a coniferous forest at Hyytiälä, Finland. We also compared simulated GPP and SIF at four Finnish micrometeorological flux measurement sites to observed GPP as well as to satellite observed SIF. Finally, we conducted a regional model simulation for the Fenno-Scandinavian region with JSBACH and compared the results to SIF retrievals from the GOME-2 (Global Ozone Monitoring Experiment-2) space-borne spectrometer and to observation-based regional GPP estimates. Both observations and simulations revealed that SIF can be used to estimate GPP at both site and regional scales. The GOME-2 based SIF was a better proxy for GPP than the remotely sensed fAPAR (fraction of absorbed photosynthetic active radiation by vegetation), even though high SIF values occurred during early spring at the northern latitudes, although these are not likely to be associated with photosynthesis.

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