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Measurement and Analysis of CO2 Fluxes and Isotopic Composition in Ecosystems

This study focuses on determining the CO2 fluxes and isotopic composition in ecosystem components such as living plant material, dead plant material, and organic matter in soils. The analysis involves incubations, Keeling plots, and mass balance equations using the LI-COR LI-6200 instrument. The results provide insights into carbon cycling and ecosystem dynamics.

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Measurement and Analysis of CO2 Fluxes and Isotopic Composition in Ecosystems

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  1. NEE => source or sink ? } RECO } GP => IRGA => MS Rnew Rold CONTEXT CO2 fluxes:

  2. F,d Fn,dn Fo,do [1] F = Fn + Fo (d-do) In situ peat respiration (gas exchange chambers and IRGA) d 13C of in situ respired CO2Determination ofdby Keeling plot d 13C of living plant material, dead plant material, organic matter in soil cores at different depth; d 13C of CO2 evolved by these materials in lab incubation [3] Fn/F = [2] F.d= Fn.dn+ Fo.do (dn- do) CALCULATIONS • Linear mixing model • Mass balance equations

  3. LICOR Li-6200 By-pass Teflon filter Dessicant (MgClO) Sampling system (Plexiglas) Butyl septum Exetainer Tube (10 ml) MATERIAL

  4. MATERIAL

  5. results : incubations

  6. results : keeling plots 1/CO2 (ppm-1) July 2004 d13 C (‰)

  7. dbp= do Frdr= Fndn+ Fodo Fada= Fndn+ Fodo data analysis July 2004 dbp=do = -20.58 ≠ -24.01 recent regeneration advanced regeneration if dn =-26.53 => Fn/Fa= 72% andFn/Fr = 40% if Fn/Fa =1O0% => dn =-24.88 andFn/Fr = 56%

  8. data analysis July 2004 October 2004 Lower values Higher variability Sample conservation??

  9. conclusions • determination of isotopic compositions of sources used for incubations this summer, and within the soil profiles (Fatima) • new series of measurements next year in spring and summer • understanding the discrepancies between: • - isotopic composition of sources (organic matter) • - isotopic composition of respired CO2 from sources (incubation) • - isotopic composition of diffused CO2 from keeling plots (keeling plots)

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