Riederer, M*; Pausch, J; Kuzyakov, Y; Foken, T: Investigation of C distribution after assimilation by combining stable isotope labeling and micrometeorological tools
Poster, 3rd iLEAPS Science Conference, Garmisch-Partenkirchen, Germany: 2011-09-18 - 2011-09-23

There is still disagreement whether grassland ecosystems are considerable carbon sinks. Separation of the C flux into several pools may advance research on this topic. We combined established methods of both, atmospheric and soil science to determine absolute C allocation in plant and soil C pools. Therefore, we chose the most intensive growth phase with respect to C uptake within the vegetation period 2010 to conduct the following experiments: Experiment I • Determination of the Net Ecosystem Exchange (NEE) by eddy covariance (EC) technique and turbulence software TK2 • Separation of NEE into ECOsystem Respiration (RECO) and Gross Ecosystem Photosynthesis (GEP) by a model based on Michaelis-Menton and Lloyd-Taylor functions • Validation of the model derived GEP by comparison with chamber measurement determined GEP ( = NEE – RECO ) Final result I: absolute C input into grassland ecosystem during 22 days of experiment Experiment II • Pulse labeling of green above ground biomass with 13CO2 and detection of the tracer in several carbon pools afterwards: soil respiration, green above ground and root biomass, rhizosphere and bulk soil • 38 days draught treatment (“1000-year-draught”) was established for further investigation considering local climate change; the combination with EC on this poster is only possible for “normal” results (EC-footprint!) • Observation of the development of the tracer excess (δ13C sample - δ13C natural abundance) after the labeling until a steady state is reached: Final result II: relative C allocation after assimilation Take home message: Combining CO2 flux measurements with isotopic labeling is predestined to quantify C sequestration in soil and C allocation within the ecosystem Outlook • Further model validation by NEE- separation with atmospheric 13CO2 fluxes determined by REA measurements (Ruppert, 2009; Wichura 2009) and consideration of other recently published separation methods • Comparison with C fluxes deter- mined by tracer recovery in total C pool size • Separation of “loss by respiration” into soil and shoot respiration • C allocation into microbial biomass

last modified 2011-09-27