Land carbon cycle managed ecosystems and climate

Galina Churkina

Institute for Advanced Sustainability Studies Potsdam, Germany

Outline

• Introduction: Role of land ecosystems in the global carbon cycle

• Drivers behind the European carbon sink

• Challenges in modeling of land ecosystems

Role of land ecosystems in the global carbon cycle

0

2

4

6

8

10

1950 1960 1970 1980 1990 2000 2010

year

Pg

C/y

r

Global anthropogenic emissions (CAntr)

0

2

4

6

8

10

1950 1960 1970 1980 1990 2000 2010

year

Pg

C/y

r

Global anthropogenic emissions (CAntr)

Remained in atmosphere (CAtm)

Absorbed by land and ocean

Airborne Fraction (AF) = CAtm/CAntr ~ 0.4 in 1950-2000

2005: Jones and Cox, JRL

Trend in AF after 2000 -?

Is AF increasing?

• Yes (Le Quere et al. Nature Geo, 2009)

• Earth’s carbon sinks are in decline

• No (Knorr, GRL, 2009, Francey et al. ICDC8, 2009)

• Earth’s carbon sinks are increasing proportionally to emissions

CAtm = CAntr - CLand- COcean

Crucial role in C uptakeUnderestimated ?

2009: Le Quere et al.,Nature Geo

(Statistics) (Model) (Model)

280

330

380

430

480

530

1860 1880 1900 1920 1940 1960 1980 2000 2020

Atmospheric CO2 Concentrations

(ice core)Observed (atmosphere)(ice core)Observed (atmosphere)(ice core)Observed (atmosphere) Management -?

Modeled with CLIMBER-BGC

2009: Churkina et al. GBC

Drivers behind the European carbon sinkChurkina et al. 2010, Biogeosciences

European ecosystems are a carbon sink of

~ 111±280 teragrams (Janssens et al. 2003)

~ 232±50 teragrams (Schulze et al. 2009)

Why Europe is a carbon sink?

Atmospheric deposition of

nitrogen

Regrowing forests/

abandment of croplands

Atmospheric deposition of nitrogen on land ecosystems of

Europe

2007: Dentener et al., GBC

2

3

4

5

6

7

8

9

10

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

year

Tg

/yr

0.1Tg/yr

0.03Tg/yr

Land cover conversion: Historical trends

2008: After Ramankutty et al., GBC

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010year

mln

sq

km crop+pasture

forest

grass

-6900sq km /yr 5800 sq km/yr

10100 sq km/yr -7000 sq km/yr

-3200 sq km/yr1100 sq km/yr

Surface Temperature of Europe

6

6.5

7

7.5

8

8.5

9

9.5

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

year

deg

C

0.02 degC/yr

0.01 degC/yr

2009: Chen et al., MPI-BGC Tech. Rep.

Atmospheric CO2

270

290

310

330

350

370

390

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

year

pp

m

1.11 ppm/yr

0.29 ppm/yr

After Etheridge et al, 1996 and Keeling & Whorf, 2005

Rates of change in environmental drivers accelerated in the second half of the 20th century

Land C balance and its drivers

C balance of Europe

ClimateAtmospheric CO2

and N deposition

Land Use (Conversion & Management)

Land Use Change

Land cover # 1

Land cover # 1*

Land cover # 2

(Change)

(Management)

(Conversion)

Although modification is not always detectable, it may have strong effect on carbon balance (forest management, fertilization, etc)

Land C balance and its drivers

C balance of Europe

ClimateAtmospheric CO2

and N deposition

Land Use (Conversion)

?

?

?

Vegetation models include:C, H2O cycles and

Land use change– JULES– ORCHIDEE

N cycle– BIOME-BGC– OCN

More details in:

2010: Churkina et al., Biogeosciences

One century of the European carbon balance

Atmospheric models: mean and uncertainty(2009:Schulze et al.)

Data compilation (2009: Schulze et al.)

European mean temperature

6

6.5

7

7.5

8

8.5

9

9.5

1950 1960 1970 1980 1990 2000 2010

ºC

OCN

Atmospheric CO2

300

310

320

330

340

350

360

370

380

390

1950 1960 1970 1980 1990 2000 2010

year

pp

m

OCN

Land cover conversion in Europe

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1950 1960 1970 1980 1990 2000 2010

year

mln

sq

km crop+pasture

forest

grass

OCN

Nitrogen deposition in Europe

3

4

5

6

7

8

9

10

1950 1960 1970 1980 1990 2000 2010

year

Tg

/yr

OCN

OCN

Is response reasonable?

0

5

10

15

20

25

30

35

40

per

cen

t

Observed* JULES ORCHIDEE BIOME-BGC

OCN

* 2005: Ainsworth & Long, New Phyt.

NPP change in response to CO2 increase of 100 ppm

Is response reasonable?

0

5

10

15

20

25

30

per

cen

t

Observed* BIOME-BGC

OCN

* 2007: Elser et al. Ecol. Letters 2008: LeBauer & Treseder, Ecology

Modeled NPP change in response to N increase by 2-28

kgN/ha/yr

Obs. NPP change in response to N increase by 1-1000 kgN/ha/yr

Conclusions• European ecosystems are a C sink

because of interactions between• CO2 fertilization effect• Climate• N deposition • land cover conversion

• C sink is likely underestimated because models do not simulate interactions of LUC and abiotic changes

Challenges in land carbon sink estimates are related to …

Land Conversion

Land Management

Extent of land use change

Luyssaert et al., in preparation

Modeling of croplands

Gap between modeled and statistical yields of wheat. Averages for 1997-2003

Ma et al. sumbitted

ton per ha

Urbanization

?7.99 ? ?4.96

0

1000

2000

3000

4000

5000

6000Pr

imar

y en

ergy

cons

umpt

ion

Was

tetre

atm

ent

Land

fills

*

Proc

ess-

base

dCO

2-em

issi

onen

Impo

rted

elec

trici

ty

Exte

rnal

milk

prod

uctio

n*Ex

tern

alce

men

tpr

oduc

tion

Oth

ers

Soil

unde

rpe

rvio

us a

reas

Fore

st

Stre

et- a

ndpa

rk-tr

ees

Hum

anin

frast

ruct

ures

(bui

ldin

gs e

tc.)

Cse

ques

tratio

n

kt (C

O2-

)C

x

Carbon Cycle of Berlin 1

2 2 11 3 3

2

2

4

Data sources1 Federal Working Committee on Energy-Balances2 Berlin Senat 3 Statistics Agency Berlin-Brandenburg4 Tree inventories of Berlin‘s districts

Direct C release Indirect C release C storage C uptakeGottschalk et al., in preparation

Land-atmosphere feedbacks