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BG2.3 - Patterns and drivers of GHG assimilation and release in natural and agricultural ecosystems
Convener: Leonardo Montagnani  | Co-Conveners: Pete Smith , Werner Leo Kutsch , Martin Wattenbach , Lutz Merbold , Paul Stoy , Christian Brümmer , Damiano Zanotelli 
 / Mon, 23 Apr, 13:30–14:15  / Room SM2

The ratio between ecosystem respiration and gross primary production determines ecosystem sink capacity. Knowledge of the relationship between carbon assimilation and respiration across time and space could allow the increasingly accurate global gross primary production estimates to be linked with those of net ecosystem production, for which reliable climatic and biological predictors at the global scale are still not available.
Autotrophic and heterotrophic respiration are both related to assimilation, with time delays ranging from seconds to years. Understanding their linkage in time and the controlling environmental drivers is key to understanding biogeochemical processes.
We will give emphasis to the role of arable systems as there are strong indications that they are a source for greenhouse gases, although the processes underlying GHG fluxes from agricultural systems are some of the least well quantified and most uncertain elements in the terrestrial biogeochemical cycle.
The session aims to bring together experimentalists and modellers to share their results on measuring carbon and water use efficiency and the relationship between assimilation and respiration, at local and global scales, as well as their findings on the environmental factors controlling the time shift between carbon assimilation and release processes.

Public information: Markku Larjavaara: The potential impacts of increasing temperatures on old-growth forest biomass density. | Alon Angert: Amazon tree stems respiration: Is the O2 influx a better measure? | Elisabeth Jerome: Carbon balance of a grazed grassland in Belgium. | Marco Matteucci: Partitioning soil CO2 fluxes by tree-girdling in a Mediterranean (Pinus pinaster) ecosystem reveals a different response of autotrophic and heterotrophic components to environmental variables and photosynthesis under drought conditions. | Miriam Hurkuck: Seasonality of atmospheric nitrogen deposition at a semi-natural peatland site. | Ben Runkle: Separating direct temperature responses from phenological control of gross photosynthesis during the short tundra growing season: measurements and process modeling from the Lena River Delta, Russia. | Marianna Deppe: Effect of experimental summer drought on greenhouse gas fluxes from soil under corn and sorghum.