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

Global Change Effects on Grasslands and Feedbacks with Regard to Greenhouse Gas Fluxes Klaus Butterbach-Bahl 1 , Xunhua Zheng 2 , Chunyan Liu 2 , Benjamin Wolf 1 , Wei Wei Chen 2 , Xinguo Han 3 and Nicolas Brüggemann 1

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

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  1. 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, Germany 2Institute for Atmospheric Physics, Chinese Academy of Sciences, Beijing, China 3Institute of Botany, Chinese Academy of Sciences . Beijing, China

  2. Forest Other Boreal Forest 17% Agro- ecosys. Temperate Forest 8% Tundra 11% Grassland Temperate Grassland 13% Scrub 3% Savanna 10% Desert 19% Tropical Rainforest 13% Mountains 6% Global importance of the biome type „grassland “

  3. Location of the target region

  4. Focus of MAGIM - I

  5. MAGIM core sites Hydrological measuring points IMGERS

  6. Climatic constraints  The climatic conditions limits NPP and make the steppe vulnerable to land use changes and grazing intensification

  7. Grazing pressure and degradation

  8. „Sustainable“ • Management • Meat/wool • Biodiversity • Water • Erosion • Atmosphere • ……. Soil properties Site/regional hydrology Plant production Species composition Biosphere/atmosphere Microbial turnover Erosion Nutrient export Feed quantity and quality Grazing effects Grazing

  9. Steppe degradation Degradation process September 2006 9.0 sheep/ha 1.5 sheep/ha

  10. Gross N turnover rates: Significant differences between grazed and ungrazed sites Holst et al., 2008, Ecosystemsc

  11. Grazed versus non-grazed steppe systems: N2O Soil T & moisture N2O-flux Soil N2O-concentr. 2007 2008

  12. Grazed versus non-grazed steppe systems: N2O Extremely high N2O-fluxes during freeze-thaw from ungrazed steppe  >70% of annual fluxes 2007 2008

  13. Do natural steppe systems emit more N2O than grazed systems? NO – On a regional scale nutrient management overrides site scale effects Holst et al., 2007, Plant and Soil

  14. Grazed versus non-grazed steppe systems: CH4

  15. Sheep CH4 emissions 10.8 -14.3 g CH4-C sheep day-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 ≈ 2.2 kg C ha-1 growing season X2 = 2.2 kg C ha-1 Do natural steppe systems take up more CH4 than grazed systems? NO – CH4 emission from riparian areas and from sheep are more important as CH4 uptake by steppe soils -50--60 µg CH4-C m-2 h-1 ≈2 kg C ha-1 growing season x0.98 = -1.96 kg C ha-1

  16. 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

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