Carbon sequestration due to the abandonment of croplands in the former USSR since 1990

Nicolas VUICHARD (1)

Luca BELELLI (1)

Irina KURGANOVA (2)

Philippe CIAIS (3)

Pascalle Smith (3)

Riccardo VALENTINI (1)

(1) University of Tuscia – Viterbo (Italy)(2) Inst. of Physiochemical and Biological Problems

in Soil Science – Pushchin (Russia)(3) LSCE/IPSL – Saclay (France)

General overview

• Soil carbon changes are impacted by

time

agriculture recovering grasslandgrassland

So

il ca

rbon

Climaxic ecosystem

+ Climate + Climate

++ Management (harvest, tillage, fert.)

+ Climate

++ Land-use legacy

50’s 90’s

Cropland’s abandonment

►Due to 1990’s economic crisis, important area of arable land has been abandoned

Arable and permanent crops in CIS (former USSR) source FAOSTAT

- 20 Mha

Abandoned cropland areas from 1990 to 2000 (Hurtt et al., 2006)

C gain estimate from plot to regional scale

Soil carbon inventoriesFlux measurements Ecosystem modeling associated with climatology and land-use change scenarios

At

the

plo

t sc

ale

At

the

reg

ion

al s

cale

Difficult to extrapolate estimate

Model-based uncertain estimate

Easy to extrapolate estimate

Data-based precise estimates

Eddy-Flux measurements

5 years 10 years more than 100 years

Hak 1natural steppe

NEE: -113.5 gC m-2 yr-1

Hak 3Cultivated from 1958 to 1993NEE: -146 gC m-2 yr-1

Hak 2Cultivated from 1958 to 1998NEE: -201 gC m-2 yr-1

Years after land-use change

Flux data from Belelli

Hak3Hak1

NE

E a

no

mal

y w

ith

Hak

1(g

C m

-2 y

r-1)

Hak2

Years after land-use change

Soil carbon inventories

NE

E(g

C m

-2 y

r-1)

Years after land-use change

Carbon accumulation in soils of abandoned croplands

C a

ccu

mu

lati

on

(tC

ha-1

)

Years after land-use change

Carbon balance of abandoned land

Soil carbon inventory based regional estimate

C gain : 131 TgC from 1993 to 2000

over 21.5 Mha

Ab

and

on

ned

lan

d(M

ha)

NE

E(T

gC

yr-1

)

Assessment of a model-based regional estimate

Gridded climate

and soil forcing

Generic Crop Model

LUE growth

Biomass allocation and yield

Water and Nitrogen balance

No soil C balancescale : field / seasonal cycle

wheat maiz

esoybean

Terrestrial Biosphere

ModelNatural ecosystem functioning

+ disturbancesscale : local => regional => global

1 year => 1000 years

Krinner et al. (2005)

Brisson et al. (2002)

• By using Orchidee-Stics

LAI

• Simple land-use change scenario

Scenario

time

agriculturegrassland

1951 1993

recovering grassland

2000

Model improvements for steppes►Modification of photosynthetic parameters values►Changes in the allocation scheme

Flux data from Belelli et al. (submitted)LAI data retrieved from FAPAR product (JRC-ISPRA)

Orchidee Orchidee-Stics

Orchidee

• Simple land-use change scenario

Scenario

time

agriculturegrassland

1951 1993

recovering grassland

2000

• N-fertilizer addition

statistics from USDA

(on arable land of former USSR)

• C export management► Harvest = grains + straw

– > We export all the harvested biomass out of the field

► Tillage -> few information on intensity

– > We assume that tillage induces a 30% decrease of the residence time of the soil carbon

Orchidee Orchidee-Stics

Orchidee

NE

E

(gC

m-2 y

r-1)

Results

Map of the C gain from 1993 to 2000 per m2

Spatial mean annual NEE

Abandonment of cultivation

Croplands100% instant. aband.Realistic aband. scenario

Croplands100% instant. aband. 1993 2000

1993

cropland

2000

537.2 gC m-2

1993 2000

recovering grassland

Results (2)

Map of the C gain from 1993 to 2000

Abandoned cropland area from 1993 to 2000

C gain from 1993 to 2000 per m2

C gain : 92 TgC in 8 years over 17 Mha

• No fertilization during cultivation => +6.1%• No tillage (no impact on soil decomposition) => -5.4%• 10% of straw remains on plot => -12.7%

Estimates comparison and 2000-2010 prediction

• C gain between 1993 and 2000

• Extrapolation for the period 2001-2010

Model-based estimate116 TgC

in 8 years over 21.5 Mha

Data-based estimate131 TgC

in 8 years over 21.5 Mha

Data-based estimate217 TgC

in 10 years over 22.8 Mha

Conclusions

• Good agreement between our 2 regional estimates

• The abandonment of crops leads to a substantial gain of C

• Improvements can be done► model approach

• To better quantify the management practices

► data approach• To obtain C accumulation for the first years after land-

use change

Thank you !

Acknowledgments to:Hurtt et al. (global land-use change map)

FAPAR team from JRC-ISPRA

Assessment of the amount of carbon sequestered

• At the plot scale

• At the regional scale

Soil carbon inventory-based studies

Flux study based on eddy-covariance measurements

Soil carbon data derived estimate Estimate based on ecosystem modeling

with land-use change scenarios

Annual NEP (gC m-2 y-1)

Period Hak1 Hak2 Hak3

Jul 2002-Jun 2003 -99 -201 X

Jan 2004-Dec 2004 -128 X -146

EC based estimate

Flux data from Belelli

Scenario

time

agriculturegrassland

1951 1991

recovering grassland

2000

Abandoned cropland areas from 1990 to 2000 (Hurtt et al., 2006)

• Simple land-use change scenario

• Region of interest80% of the abandoned croplands

are located between 20°-40°E and 40°-

60°N

Model improvements for steppes

• On the Hak1 site (54.5°N 90°E)►Modification of photosynthetic parameters values►Changes in the allocation scheme

Flux data from Belelli et al. (submitted)

LAI data retrieved from FAPAR product (JRC-ISPRA)

Hypothesis / Simplification

• Fertilization

• C export management of croplands► Harvest = grains + straw

– > We export all the harvested biomass out of the field

► Tillage -> few information on intensity– > We assume that tillage induces a 30% decrease of the time of

residence of the soil carbon

statistics from USDA (1965-1985 on arable land of former USSR)

Assessment of a regional estimate

Vegetation map Agricultural practicesGridded climate/soil forcing

LAI

Vegetation height

Irrigation

Nitrogen stress index

Generic Crop Model

LUE growth

Biomass allocation and yield

Water and Nitrogen balance

No soil C balancescale : field / seasonal cycle

wheat maiz

esoybean

Terrestrial Biosphere

ModelNatural ecosystem functioning

+ disturbancesscale : local => regional => global

1 year => 1000 years

Krinner et al. (2005) Brisson et al. (2002)

• By using Orchidee-Stics mechanistic model