RELATIONSHIP BETWEEN SUNAND GROSS PRIMARY PRODUCTION IN A WHEAT CROP

Goulas Y.*, Fournier A.*, Daumard F.*,

*Laboratoire de Météorologie Dynamique, Centre National de la Recherche Scientifique, Ecole Polytechnique, 91128 Palaiseau Cedex, FrancePolytechnique, 91128 Palaiseau Cedex, France

+ Institut National de la Recherche Agronomique (INRA), Avignon, France

1. Introduction1. IntroductionChlorophyll fluorescence (ChlF) is a light emission produced by photosynthetic pigments from their excitedcompetes with other deactivation pathways such as pototochemistry and heat dissipation. At leaf level,Development of new techniques based on the filling-in of absorption bands in the solar spectrum enablespossibilities of remote sensing of vegetation fluorescence (Plascyk 1975, Moya et al. 2004, for aempirically show a strong linear correlation between sun-induced fluorescence (SIF) and gross primaryHowever, the rationale of the observed correlation still remains unclear. Here, we investigated theHowever, the rationale of the observed correlation still remains unclear. Here, we investigated theseasonal cycle and analyzed how it is affected by experimental conditions and environmental parameters

SIF has been measured in the oxygen absorption bands at two wavelengths (red , F687; far red, F760) at the Avignon experimental site with

2. Measurements of sun-induced fluorescence (SIF) and gross2. Measurements of sun-induced fluorescence (SIF) and gross

Eddy tower

Eddy footprint

SIF target

SIF fov

The SIF instrument Triflex mounted on acrane at the Avignon experimental site.(Daumard et al., 2010, 2012

3. Correlations between SIF and GPP3. Correlations between SIF and GPP

experimental site with the TriFlex instrument build in LMD (Daumardet al. 2010).

A strong correlation is found between GPP and F760

The correlation is much weaker between GPP and F687

Meteo station

SIF fov

Aerial view of the Avignon experimental site atINRA (Institut National de la RechercheAgronomique).

50

40

30

GPP

(µm

oles

C m

-2 s

-1 )

r 2

=0.8350

40

30

GPP

(µm

oles

C m

-2 s

-1 ) r

2=0.34

4. Analysis of the SIF-GPP relationship4. Analysis of the SIF-GPP relationship

GPP APAR LUE ThefactorsWe

GPP and F760 when data are integrated over the day (r2=0.83).

and F687 (r2=0.34).

The relationship between GPP and SIF was analyzedwith simple models following Monteith’s approach ofcanopy productivity (Monteith 1972). As fluorescence

30

20

10

0

GPP

(µm

oles

C m

2.0x101.51.00.50.0

F760 (W m-2 sr-1 nm-1)

30

20

10

0

GPP

(µm

oles

C m

6004002000

F687 (W m-2 sr-1 nm-1)

F F

GPP APAR LUESIF APAR

WeAPAReddyfluorescencethe

Fluorescence yield:Results show that variation range of Fis limited (25-35%) compared to LUE(280%). F shows a biphasic variationpattern with PAR: it increases with PAR

canopy productivity (Monteith 1972). As fluorescenceemission and photosynthesis both occur from energyabsorbed by photosynthetic pigments, GPP and SIFshare a common factor: the AbsorbedPhotosynthetically Active Radiation (APAR).

High Low

25x10-6

20

15

F760

/PA

R (n

m-1

)

0.45

0.40

0.35

0.30

0.25

F

Relationship betweennormalization: Underrelationship is almostand low light levels

Reabsorption factor:The role of F in SIF can be assessed bymonitoring the fluorescence emissionratio (F760/F687) during periods whenchlorophyll content remains stable.

pattern with PAR: it increases with PARat low to moderate irradiation levels anddecreases over 1000 moles m-2 s-1. Fpoorly correlates with LUE (r2=0.11),which induces a decorrelation in the SIF-GPP relationship.

10

5

0

F760

/PA

R (n

m-1

)

0

GPP/PAR (moles C/moles quanta)

3.5

3.0

2.5

2.0

F760

/F68

7

0.20150010005000

PAR (moles/m2/s)

0.4

0.3

0.2

0.1

0.0

F

40x10-33020100LUE (moles C/ moles photons)

r2=0.11

5. Conclusions5. Conclusions A strong correlation is found between daily GPP and far red fluorescence (F760). Variations of APAR induced by canopy develop

GPP and red fluorescence (F687) are poorly correlated.

LUE variations are not reflected by proportional fluorescence yield variations.

Red emission at 687 nm is strongly impacted by reabsorption of fluorescence through canopy, depending on geometry.

and low light levelsregression line (redin a loss of correlation

chlorophyll content remains stable.Results show that F strongly depends oncanopy development and on illuminationgeometry (Fournier et al. 2012).

2.0

1.5

1.0

0.5

F760

/F68

7

0.50.40.30.20.1

Vegetation height (m)

This work has been undertakenwith the support from : PNTS

Red emission at 687 nm is strongly impacted by reabsorption of fluorescence through canopy, depending on geometry.

Fluorescence must be corrected for APAR and F variations to be interpreted in terms of physiological state (

6. References6. ReferencesDaumard, F., et al., IEEE Transactions in Geoscience and Remote Sensing, 2010. 48(9): p. 3358-3368.Daumard, F., et al., IEEE Transactions on Geoscience and Remote Sensing, 2012. 50(11): p. 4292-4300.Fournier, A., et al, ISPRS Journal of Photogrammetry and Remote Sensing, 2012. 68(0): p. 112-120.Frankenberg, C., et al., Geophys. Res. Lett., 2011. 38(17): p. L17706.

Joiner, J., et al., Biogeosciences, 2011. 8(3): p. 637Kowalski, S., et al., Global Change Biology, 2003. Meroni, M., et al., Remote Sensing of Environment, 2009. Monteith, J.L., Journal of Applied Ecology, 1972.

RELATIONSHIP BETWEEN SUN-INDUCED FLUORESCENCE AND GROSS PRIMARY PRODUCTION IN A WHEAT CROP

Goulas Y.*, Fournier A.*, Daumard F.*, Ounis A.*, Marloie O.+, Moya I.*

*Laboratoire de Météorologie Dynamique, Centre National de la Recherche Scientifique, Ecole Polytechnique, 91128 Palaiseau Cedex, FrancePolytechnique, 91128 Palaiseau Cedex, France

Institut National de la Recherche Agronomique (INRA), Avignon, France

excited state. It is regarded as a promising tool for remote sensing of photosynthetic activity since itlevel, ChlF is widely used to evaluate photosynthetic activity at the laboratory or in the field.enables to quantify the fluorescence emission excited by natural light and considerably extends thereview see Meroni et al 2009). Global maps of vegetation fluorescence have been produced that

primary production (GPP) (Joiner et al. 2011, Frankenberg et al. 2011).the SIF-GPP relationship on a wheat crop (Triticum turgidum durum, cultivar Daker) over a completethe SIF-GPP relationship on a wheat crop (Triticum turgidum durum, cultivar Daker) over a complete

parameters (PAR, growth stage, emission wavelength, integration time).

gross primary production (GPP) on a wheat cropgross primary production (GPP) on a wheat crop

50403020100m

oles C

m-2

s-1

2.0

1.5-1 nm

-1

0.80.60.40.20.0mW

m-2

sr-1

nm-1

2000

1500

1000

500

0

mole

s m-2

s-1

F687

F760

GPP

PARCO2 fluxes were measured continuously using the eddy covariance technique at 30 mn intervals. Net CO2 fluxes were partitioned into GPP and

1601401201008060day of the year

1.5

1.0

0.5

0.0mW m

-2sr-1

nm F760

When considering 30 mnintervals data, the correlation is weaker for the GPP-F760 relationship

partitioned into GPP and ecosystem respiration following the method described in Kowalski et al. 2003. Time course of canopy variables and remote sensing signals over a seasonal cycle from March

1st to June 19th 2010.

50

40

30

GPP

(µm

oles

C m

-2 s

-1 ) r

2=0.63 50

40

30

GPP

(µm

oles

C m

-2 s

-1 ) r

2=0.31

The level of correlation between GPP and SIF is dependent on the relationships between the otherfactors: LUE (Light Use Efficiency), F (fluorescence yield at leaf level) and F (reabsorption factor).We investigated these factors by means of independent measurements at leaf and canopy level.

the GPP-F760 relationship (r2=0.63), while it is unchanged for red fluorescence (r2=0.31).

30

20

10

0G

PP (µ

mol

es C

m2.0x101.51.00.50.0

F760 (W m-2 sr-1 nm-1)

30

20

10

0

GPP

(µm

oles

C m

800x106004002000

F687 (W m-2 sr-1 nm-1)800x10

Relationship between GPP and SIF for 30mn intervals data.

We investigated these factors by means of independent measurements at leaf and canopy level.APAR was estimated from light transmitted through canopy. LUE was derived from GPP obtained byeddy covariance. A relative value of fluorescence yield F was obtained by measuring stationaryfluorescence under constant excitation with a PAM-2000 fluorometer on randomly selected leaves inthe canopy.

growthmaturity

senescence0.8

coef

ficie

nt r

2

LAI maximizedCorrelation of GPP with PAR, F760 and F687 are within the same range

LAI increaseHighest correlation of GPP with F760 and LAI

High irradianceLow LUE

Low irradianceHighLUE

between SIF and GPP after PARUnder moderate incident light, the

almost linear (green points). Highlevels induce a deviation from the

senescence0.8

0.6

0.4

0.2

0.0

r2

60-130 70-140 80-150 100-160Time period

GPP-F760

GPP-PAR

GPP-F687

GPP-LAI

Pear

son’

sco

rrel

atio

nco

effic

ient

r

Regression time period

Decrease in ChlCorrelation with F760 increases(no LAI measurement)

Correlation coefficient of the linear regression betweenGPP and canopy variables (F760, F687, PAR, LAI) as afunction of the time period considered for regressionanalysis. Highest correlation is obtained for F760 during

60x10-35040302010

GPP/PAR (moles C/moles quanta)

140012001000800

Mean daily irradiance (moles m-2 s-1)

A strong correlation is found between daily GPP and far red fluorescence (F760). Variations of APAR induced by canopy development are the main source of correlation.

of fluorescence through canopy, depending on geometry.

levels induce a deviation from the(red and blue points), which results

correlation in the SIF-GPP relationship.

analysis. Highest correlation is obtained for F760 duringgrowth. When crop is in a steady state, GPP correlatesat the same level with F760, F687 and PAR.

of fluorescence through canopy, depending on geometry.

variations to be interpreted in terms of physiological state (F).

8(3): p. 637-651.Global Change Biology, 2003. 9(7): p. 1051-1065.Remote Sensing of Environment, 2009. 113(10): p. 2037-2051.

Journal of Applied Ecology, 1972. 9(3): p. 747-766.

Moya, I., et al., Remote Sensing of Environment, 2004. 91(2): p. 186-197.Plascyk, J.A., Optical Eng., 1975. 14(4): p. 339-346.