Global Change Effects on Grasslands and Feedbacks with Regard to Greenhouse Gas Fluxes

K. Butterbach-Bahl | ERSEC International Conference| 05/05/09

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Global Change Effects on Grasslands and Feedbacks with

Regard to Greenhouse Gas Fluxes

Klaus Butterbach-Bahl1, Xunhua Zheng2, Chunyan Liu2, Benjamin

Wolf1, Wei Wei Chen2, Xinguo Han3 and Nicolas Brüggemann1

1Institute for Meteorology and Climate Research, Garmisch-Partenkirchen, Germany2Institute for Atmospheric Physics, Chinese Academy of Sciences, Beijing, China

3Institute of Botany, Chinese Academy of Sciences . Beijing, China



Global importance of the biome type „grassland “

Boreal Forest17%

TemperateForest 8%

TemperateGrassland 13%

Savanna10%

TropicalRainforest 13%

Mountains6%

Desert19%

Scrub3%

Tundra11%

10.8%

17.8%

39%

32.4%

Forest

Grassland

Agro-ecosys.

Other



Location of the target region



Focus of MAGIM - I



IMGERS

MAGIM core sitesHydrologicalmeasuring points



Climatic constraints

The climatic conditions limits NPP and make the steppe vulnerable to land use changes and grazing intensification

Precipitation [mm]

Mean 343.4

2003 371.3

2004 324.6

2005 166.1



Grazing pressure and degradation



Grazing

Soil properties

Plant production

Microbial turnover

Nutrient export

Species composition Biosphere/atmosphere

Site/regional hydrology

Erosion

Feed quantity and quality

„Sustainable“Management• Meat/wool• Biodiversity• Water• Erosion• Atmosphere• …….

Grazing effects



Degradation process

1.5 sheep/ha9.0 sheep/ha

September 2006

Steppe degradation



Gross N turnover rates: Significant differences between grazed and ungrazed sites

0.0

2.5

5.0

7.5

10.0

HGWG

UG99UG79

Ammonification Nitrification

Gro

ss N

tu

rno

ver

[µg

N g-1

SD

W d

ay-1

]

2005

June July August Sept. June July August Sept.0.0

2.5

5.0

7.5

Hol

st e

t al

., 2

008

, E

cosy

stem

sc



Soil N2O-concentr.

N2O-flux

Soil T & moisture

Grazed versus non-grazed steppe systems: N2O

2007 2008



Extremely highN2O-fluxes during freeze-thaw from ungrazed steppe

>70% of annual fluxes

Grazed versus non-grazed steppe systems: N2O

2007 2008



Do natural steppe systems emit more N2O than grazed

systems?

0

2

4

6

8

10

12

14

-30

-20

-10

0

10

20

30

N2O

flu

x (N

2O-N

mg

m-2

h-1

) Daily air tem

peratu

re (°C)

1 1.5 2 2.5 30

25

50

75

Stocking rate [sheep ha -1]

N2O

-flu

x [g

N h

a-1

ve

ge

tatio

n p

eri

od

]

Upland steppe Riparian area Urine patches Sheepfold Dung heap

NO – On a regional scale nutrient management

overrides site scale effects

Holst et al., 2007, Plant and Soil



Grazed versus non-grazed steppe systems: CH4

UG WG

Texture sL sL

pH 6.8±0.3 6.7±0.3

SOC [%] 2.5±0.6 2.6±0.5

Bulk dens.[g cm-3]

1.09±0.1 1.09±0.1

Gas Perm.-30kPa [cm d-1]

99.6±67 55.5±38



Do natural steppe systems take up more CH4 than grazed

systems?

H1 H2 H3 H4 H5 H6 H7 H8

-60

-50

-40

-30

-20

-10

0

10

CH

4 flu

x (µ

g C

H4-C

m-2 h

-1)

-50--60 µg CH4-C m-2 h-1

≈2 kg C ha-1 growing season

x0.98 = -1.96 kg C ha-1

Sheep CH4 emissions10.8 -14.3 g CH4-C sheep day-1

≈ 2.2 kg C ha-1 growing season

X2 = 2.2 kg C ha-1

1.1 mg CH4-C m-2 h-1

≈ 70 kg C ha-1 growing season

X0.02 = 1.4 kg C ha-1

NO – CH 4 emission fro

m riparian areas and from sheep

are more important as CH 4 uptake by steppe soils



Summary

• Grazing management has largely affected the biosphere atmosphere exchange of N2O:

• decreasing winter emissions• increase in N2O emissions from sheep folds

• as well as of CH4:

• Decreasing uptake of CH4

• Increasing emissions from sheep • Understanding of GHG fluxes on a regional scale

requires a detailed system analysis

Global Change Effects on Grasslands and Feedbacks with Regard to Greenhouse Gas Fluxes

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