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Drivers of C sink activity in European grasslands inferred from flux measurements

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HAL Id: hal-02820786

https://hal.inrae.fr/hal-02820786

Submitted on 6 Jun 2020

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Drivers of C sink activity in European grasslands inferred from flux measurements

Jean-François Soussana, Katja Klumpp, Romain Lardy, Tiphaine Tallec

To cite this version:

Jean-François Soussana, Katja Klumpp, Romain Lardy, Tiphaine Tallec. Drivers of C sink activity in

European grasslands inferred from flux measurements. International Symposium on Soil Organic Mat-

ter Dynamics : Land Use, Management and Global Change, United States Department of Agriculture

- USDA (USA) (USDA). USA., Jul 2009, Colorado Springs, United States. 19 p. �hal-02820786�

(2)

SOM symposium,

Colorado Springs, July 7, 2009

A L I M E N T A T I O N A G R I C U L T U R E

E N V I R O N N E M E N T

Drivers of C sink activity in European grasslands inferred from flux

measurements

Jean-François Soussana 1 , Katja Klumpp 1 , Romain Lardy 1 , Tiphaine Tallec 1

and CarboEurope grassland and wetland activity members.

1. INRA, Grassland Ecosystem Research (UR 874, UREP)

Clermont-Ferrand, France

(3)

C fluxes in a grassland ecosystem

(Soussana and Tallec, 2009, Animal, in press)

F CH4 F CO2

F leach

F animal-products

F manure

F harvest

F erosion F fire

F VOC

Net carbon storage

Figure 1

F CH4 F CO2

F leach

F animal-products

F manure

F harvest

F erosion F fire

F VOC

Net carbon storage

Figure 1

(NBP) NEE

Measurements at grassland and wetland sites in CarboEurope IP project Simplified carbon balance (Net Biome Productivity) :

NBP = (NEE - F CH4-C ) + (F manure - F harvest – F animal-products ) – F leach

(4)

Annual NBP of grasslands and wetlands (89 site-years)

Annual Net Biome productivity (NBP, gC m -2 yr -1 )

-600 -400 -200 0 200 400 600 800

Grasslands: median 98 gC m -2 y -1 (P<0.001)

Wetlands: median 62 gC m -2 y -1 (P<0.001)

21 grasslands sites (3 sown); 7 wetland sites.

3 sites out of 28 are C sources to the atmosphere

C source C sink

(5)

GPP 1189

NBP 98

R eco

1037

Cut 76

Intake 70 Manure

40

Enteric fermentation

6 Leaching

12

Mean carbon fluxes (g C m -2 yr -1 ) at European grassland sites

NEE 152

(6)

Simple C cycle model (5 state variables, 3 soil parameters)

C plant C litter C active C slow C passive

GPP

C export

C intake

1

C import

f (T,P) K 2

( 1-d-k CH4 )C intake

f (T,P) (1-K 2 ) f (T,P) (1-K 2 ) K 2

f (T,P) K 2 2

f (T,P) k slow

f (T,P) k stab

R h-litter

(1-K 1 )GPP

R h-active R h-slow

R a

(d+k CH4 )C intake

R h-animal

Daily time step. Forced by measured C fluxes (except Reco) Predicts Reco and NBP

C plant , C litter and C active initialised at equilibrium

C slow initialised from SOC (0-30 cm) measurements

Measured Modelled

Ecosystem respiration, Reco

(7)

Fitted temperature and precipitation response functions of soil respiration

Plot of (0.115*40+M_P*(1-0.115))/(40+ M_P*(1-0.115)) vs M_P

M_P

(0 .1 1 5 * 4 0 + M _ P * (1 -0 .1 1 5 ))/ (4 0 + M _ P * (1 -0 .1 1 5 ))

0 30 60 90 120 150 180 0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

f(P )

P (mm)

 

 

 

 

 

  0 0

1 1

) 1

(

) 1

( ) .

,

( T T T T

Ea

e ref

P k

P P k

T

f

Plot of EXP(350*(1/(10+46.02)-1/(Tair+46.02))) vs Tair

Tair

E X P (3 5 0 * (1 /(1 0 + 4 6 .0 2 )-1 /(Ta ir + 4 6 .0 2 )))

-1 3 7 11 15 19

0 0.4 0.8 1.2 1.6 2 2.4

f(T )

POM: Ea=350K SOM: Ea=450K

(Lloyd and Taylor, 1994 for temperature)

(8)

Fitting model to daily Reco and annual NBP data

Monte-Carlo procedure mean (mean s.e. for 10 runs) Mean slow C initial = 16.5 (0.48)

Mean K 2 = 0.32 (0.018)

Mean K slow = 0.013 (0.0016) Mean K stab = 0.0059 (0.00105)

(AT-Neustift site)

R 2 =0.98, n=6

R 2 =0.88, n=2120

(9)

Measured vs. simulated Reco and NBP for 20 sites

(with optimized K 2 , K slow , K stab )

Simulated daily Reco (gC m -2 d -1 )

0 1 2 3 4 5 6

M ea s ur ed da ily R ec o ( g C m

-2

d

-1

)

0 1 2 3 4 5 6

n=20 y = 1.01 x R

2

= 0.98

RECO:1 vs #Reco Plot 1 Regr

Simulated annual NBP (gC m -2 d -1 )

-300 -200 -100 0 100 200 300 400 500

M ea s ur ed an nu al N BP ( g C m

-2

d

-1

)

-300 -200 -100 0 100 200 300 400 500

n=20

y = 1.07 x

R

2

= 0.92

(10)

Variation among sites in soil parameter values

0.0001 0.001 0.01 0.1 1

K2 Kslow Kstabilisation

(unitless, log scale)

(11)

Silt (%)

0 20 40 60 80

K

stab

( s tabilisatio n c oef fic ient , y r

-1

) 0.002 0.004 0.006 0.008 0.010

SILT_% vs kstab

Best fits for soil parameters

Precipitation / Potential evapotranspiration

0.0 0.5 1.0 1.5 2.0 2.5

K

2

( hum if ic at ion c oef fic ient )

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

P/ETP vs K2squared

N balance (g N m

-2

yr

-1

)

-30 -20 -10 0 10 20 30 40

K

slow

( turnov er coef fic ient , y r

-1

)

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035

N_balance vs FkslowOffset

Grassland sites

n=15, P<0.01 Grassland sites

n=15, P<0.017

Grassland sites n=15, P<0.013

Humification (K 2 ) varies with P/ETP

Stabilisation (K stab ) varies with % silt

Slow C

turnover (K slow )

varies with N

balance

(12)

Simulated vs. measured annual NBP with fitted soil parameters

Simulated annual NBP (gC m -2 d -1 )

-200 0 200 400

M eas ur ed annual N BP ( g C m -2 d -1 )

-200 -100 0 100 200 300 400

n=14

y = 0.76 x +17 R2 = 0.60, P<0.007

C sink activity is inferred from GPP, climate, management and texture

(13)

N = atmospheric N deposition (EMEP)+N fertiliser supply

Annual GPP varies with

temperature (T), precipitation (P) and N

GPP = (N s +e) (a P + b P 2 ) / (1 + ((T – c)/d) 2 ) (n=84, r 2 =0.748, P<0.0001)

0 500 1000 1500 2000

0 2

4 6

8 10

12 14 16 18 20

400 200 800 600 1200 1000 1600 1400 1800 GPP

(g C m

-2

y r

-1

)

M ean ann

ual t emper

ature (°C

)

Mean annual pr

ecipitat ion (mm )

GPP vs. rainfall and temperature N supply: 40 g N m-2 yr-1

0 500 1000 1500 2000 0

500 1000 1500 2000

0 2

4 6

8 10

12 14 16 18 20

400 200 800 600

1200 1000 1400 GPP

(g C m

-2

y r

-1

)

M ean annu

al tem peratu

re (°C )

Mean annu al prec

ipitation (mm)

GPP vs. rainfall and temperature 0 N supply

0 N 40 g N m -2 yr -1

(14)

European grasslands statistics

Simple model upscaled to the scale of Europe

(15)

A first estimate of carbon sequestration in European grasslands

C sink (NBP) reaches 6 % of gross photosynthesis, similar to forests Direct plus indirect emissions of N 2 O and CH 4 lead to a 45 % trade-off

(Soussana et al., in prep.)

(16)

The GHG balance of the agriculture sector in Europe

Grassland C sequestration would play a

significant role for the European agriculture sector

GHG balance of agriculture in EU25 including C sequestration

Tg C yr -1

-40 -20 0 20 40 60 80

Grassland Cropland Undisturbed peat Drained peat CH4 N2O

(Schulze et al., submitted to Nature Geosciences)

(17)

Atmospheric CO 2 N supply

Temperature Precipitation

C sink (NBP) sensitivity over 100 yrs (CH-Oensingen)

Mean annual precipitation (mm)

C um ul a te d N B P , 1 0 0 y rs ( gC m -2 )

Mean annual temperature (°C)

M e a n c u m u la te d N B P i n 1 0 0 y rs ( g C m -2 )

CO2 concentration (ppm)

C um ul a te d N B P , 1 0 0 y rs ( gC m -2 )

N supply (kg N ha-1 yr-1)

C um ul a te d N B P , 1 0 0 y rs ( gC m -2 )

?

(18)

Attribution of grassland C sink

(gC m -2 yr -1 )

• Global change

1°C warming -1 80 ppm CO 2 rise 19 Atm. N deposition 3

• Direct anthropogenic

Land use/management 12 (inferred)

2/3 of the current C sink would be caused by global change

(19)

Conclusions

• Improved understanding by inferring soil C dynamics from C flux measurements

• Model shows a major role of nutrients deficiency which accelerates C turnover (priming effect, Fontaine & Barot, 2005)

• This simple model can be used for upscaling and attributing C sink to either global change or direct anthropogenic activity (UNFCCC)

• More complex models (e.g. CENTURY included in

PASIM) do not yet have the same predictive ability

(20)

Thank you

Références

Télécharger maintenant ( PDF - 20 Page - 3.05 MB )

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