Modelling the response of wheat canopy assimilation to

Modelling the response of wheat canopy assimilation to

Modelling the response of wheat canopy assimilation to CO 2 using two
models of different level of empiricism
D Rodriguez1,2, F Ewert3, J Goudriaan1, JR Porter3, R Manderscheid4, S Burkart4, RAC Mitchell5 & HJ Weigel4
1
Department of Plant Sciences, Wageningen University, The Netherlands, 2 Dept. Suelos, Facultad de Agronoma, Universidad de Buenos
Aires, Argentina, 3 Department of Agricultural Scences, Royal Veterinary & Agricultural University, Denmark,
4
Bundesforschungsanstalt fr Landwirtschft, Germany, 5 IACR-Rothamsted, Harpenden, UK

Objective
Future increase in CO2 concentration will affect wheat growth and yield primarily through increase in assimilation rate per unit leaf area. While many studies have
investigated CO2 effects on leaf photosynthesis, little is known about the integration of responses and up-scaling from the leaf to the canopy. The objective of this
work was to compare observed hourly values of canopy assimilation at two levels of CO2, with simulations from two models with different level of complexity.

Models & Data
The models simulate crop assimilation using either a simple light response
curve equation (AFRCWHEAT2) or detail calculations of leaf energy balances,
and the coupling of photosynthesis with stomatal conductance (LINTULCC2).
LINTULCC2 up-scales leaf gas exchange to canopy as proposed by Leuning
(1995). It uses concepts of the sun/shade model (de Pury & Farquhar, 1997), of
responses of stomata to photosynthesis, external CO2 and water availability
(Wang & Leuning (1998), and a description of the biochemistry of
photosynthesis (Farquhar et al., 1980). Both models allow for the within day
variations in temperature, radiation and vapour pressure deficit.

Hourly values of net assimilation (Pn, mol CO2 m-2 s-1) and
evapotranspiration (ET, mmol H2O m-2 s-1), together with weather inputs were
obtained from an OTC experiment (ambient 380 and high 670 mol mol-1)
with spring wheat (cv. Minaret) at Braunschweig, Germany. Both models
used the same input values for LAI. Observed and simulated values of hourly,
and daily total Pn, and instantaneous ET were compared at 50, 64, 89, 103,
54, 68, 94 and 105 days after emergence of the crop.

Results & conclusions

50
40
30

-1
-2

60
40
20

High = 0.8048x + 6.455
R2 = 0.5916

0
20

40

60

80
-2

100

AFRCWHEAT2
Low = 0.6334x + 4.7298
R2 = 0.8406

80
60
40
20

High = 0.8275x - 1.434
R2 = 0.8396

0

100

0

-1

Observed DTNA [g CO 2 m d ]

20

20
40
60
80
100
-2 -1
Observed DTNA [g CO2 m d ]

Figure 2. Simulated versus observed values of daily total assimilation (DTNA) for
ambient and high CO2 crops calculated by both models.

0

15

y = 0.7841x + 1.3245
R2 = 0.7247

10

5

LINTULCC2
0
5
10
15
Observed ET [mmol H2O m-2 s -1]

y = 0.8216x + 0.9566
R2 = 0.7911

15 Low = 0.9823x

10

R 2 = 0.5088
High =0.9922x
R 2 =0.626

5
LINTULCC2
0

10

Low =0.6652x
R 2 =0.079

15

1:1 Line

High =0.6911x
R 2 =0.0909

10

5
AFRCWHEAT2
0

0

5
10
15
Obs. RUE [g CO2 MJ-1 PAR]

0

5
10
15
Obs. RUE [g CO2 MJ-1 PAR]

Figure 3. Simulated versus observed radiation use efficiency (RUE) for LINTULCC2
and AFRCWHEAT2
5

LINTULCC2
0
0

5
10
15
Observed ET [mmol H2O m-2 s -2]

Figure 4. Simulated versus observed canopy evapotranspiration for ambient (open circles)
and high (closed circles) CO2, simulations are by LINTULCC2.

EU IMPETUS

Irrespective of the CO2 treatment both models reproduced well the
observed values of radiation use efficiency calculated as the ratio between
DTNA and daily intercepted PAR.
Sim. RUE [g CO2 MJ-1 PA R]

10

Simulated ET [mmol 2HO m-2 s -1]

Simulated ET [mmol 2HO m-2 s -1]

Low = 0.7244x + 9.0348
R2 = 0.6439

80

0

Figure 1. Simulated and observed canopy instantaneous Pn for ambient (open circles) and
high (closed circles) CO2. Simulations by LINTULCC2 (continuous lines) and
AFRCWHEAT2 (dashed lines).

0

LINTULCC2

100

-2

-1

2 m d ]
Simulated DTNA [g CO

60 50 DAE

0 2 4 6 8 10 12 14 16 18 20 22 24

15

Predictions of both models had similar errors for hourly and daily total values
of assimilate production.

Sim. RUE [g CO2 MJ-1 PA R]

Pn [umol CO

2

m -2 s -1 ]

..

2 m d ]
Simulated DTNA [g CO

Irrespective of the developmental stage of the crop the models were able to
capture the main signals from the environment

As LINTULCC2 calculates stomatal conductance this model allows us to
study the simulated response of crop evapotranspiration (ET) to the ambient
CO2 which is of particular importance in rain fed crops.
We conclude that for well-irrigated conditions a simple approximation based
on a light response curve avoiding the calculation of the coupling between
photosynthesis and stomatal conductance could be used. When water
supply is not optimal a more detailed approach might be needed to
reproduce the interactive effects between CO2 and water supply on
assimilation and transpiration.

Recently Viewed Presentations

  • The PRACE Initiative Catherine RIVIERE, CEO of GENCI

    The PRACE Initiative Catherine RIVIERE, CEO of GENCI

    PRACEThe Partnership for Advance Computing in Europe is the European HPC Research Infrastructure. Enabling world-class science through large scale simulations. Providing HPC services on leading edge capability systems on a diverse set of architectures
  • Verbs - Dysart High School

    Verbs - Dysart High School

    jump. What is an action verb? A verb is one of the most important parts of the sentence. It tells the subjects actions, events, or state of being. It is always found in the predicate of a sentence. A verb...
  • From Slavery to Freedom 9th ed.

    From Slavery to Freedom 9th ed.

    The James Reese Europe Orchestra. ... Joined Fletcher Henderson's orchestra in 1924. Despite differing styles, Armstrong transformed New York's big-band jazz; new rhythmic momentum and improvisational boldness. ... From Slavery to Freedom 9th ed.
  • Yearbook Vocabulary!

    Yearbook Vocabulary!

    SPIN-OFFS Creative, alternative titles for the yearbook sections that relate to the theme and give the book variety. DIVIDER These spreads separate sections of the book such as Academics, Sports, People, Student Life, Clubs, and Ads. All dividers will follow...
  • Title Goes Here - The Committee on Earth Observation ...

    Title Goes Here - The Committee on Earth Observation ...

    Committee on Earth Observation Satellites. Report & Lessons Learned. Presenter Guidance. Note the time allocated for your topic and match the number of slides accordingly. For the Agency, WG, GEO presentations (Agency numbers 6 - 22): ... Lessons learned in...
  • Welcome to our Calculation Meeting

    Welcome to our Calculation Meeting

    Examples from our children… Addition. By Year 1 . Jottings (pictures) By Year 2. Number line representation. By Year 3/4. Column addition, no regrouping. By Year 3/4 . Column addition with regrouping. By Year 5. Column addition with three numbers....
  • NPQH Final Assessment  Write and submit an account

    NPQH Final Assessment Write and submit an account

    NPQH S and I (Strategy and Improvement) Ref : NPQH FA submission form. Key question: How have you collaborated with the governing board to draw up plans to improve pupil progress and attainment, which take into account changes taking place...
  • WELCOME to Mr. Reeds (A106) Intro to Eng.

    WELCOME to Mr. Reeds (A106) Intro to Eng.

    Semester Exam 20%. PLTW classes - you will . ALL. have to take the EOC. Some students will be eligible to skip the 2. nd. Semester Finals, which will be different from the PLTW EOC's, but EVERYONE takes the 1....