RESULTS Estimating a carbon balance of a sunny summer day in Frasne bog First field measurement campaigns were performed this summer on June 25 th (CO 2 + CH 4) and September 7-8 th (CO 2) Paris Nancy Frasne 100 kms In this context, in situ CH 4 and CO 2 exchange measurements were set up and CO 2 isotopic discrimination of respiratory fluxes characterized in relation to temperature treatment (OTC) and soil humidity gradient (Wet and Dry sites) along the Frasne bog as described below. REFERENCES 1 PEATWARM: this european project examines to what extent climatic warming can modify the functioning of peatlands in temperate regions and thus to deteriorate their carbon sink function investigating the effects on (1) vegetation, (2) the balance of above-and belowground C fluxes (especially by the isotopic signature of respired CO2), (3) microbial diversity and activity in Sphagnum mosses and peat, and (4) the dynamics of labile and recalcitrant OM of the peat substrate. Main coordinator: Fatima Laggoun-Defarge (ISTO-Orléans, France). ðThe characterization under controlled conditions of individual and global responses of gas exchange and isotopic discrimination of plant and peat samples to temperature and substrate moisture using an incubator coupled with a tunable diode laser spectrometer (TDLS) is in progress. ðIn addition to the continuous CO 2 exchange measurements, two CH 4-SPIRIT campaigns are planned for 2010 to explore the temporal variability of these emissions. ðThese data will be involved in the preparation of a peatland-based carbon biogeochemical model including the response to temperature and moisture disturbances of the different above-ground compartments.