Water and carbon transfers between peatlands, atmosphere and aquifers : Hydrological, geochemical and greenhouse gas flux models of the active peatland of Frasne (Jura Massif, France) ; Transferts d'eau et de carbone entre les tourbières, l'atmosphère et les aquifères : Modèles hydrologiques, géochimiques et de flux de gaz à effet de serre de la tourbière active de Frasne (Massif du Jura, France)

Peatlands are wetlands furnishing many ecosystem services (carbon storage; water storage/filtration,specific biodiversity, climate archives). While these services have a key role to address the challenges of the 21st century - climate, biodiversity, and water resources - they are directly threatened by human activities (drainage) and climate change. Understanding the hydrological, biogeochemical, and ecological mechanisms of peatlands functioning at different spatio-temporal scales is therefore fundamental to mitigate these impacts (management, restoration) and assess the water and carbon dynamics of peatlands over the next decades. It is in this context that this work focuses on the functioning of the “active peatland” of the Forbonnet (municipality of Frasne, Doubs). This sphagnum-dominated peatland is characteristic of mid-mountain temperate environments and is located in a syncline of a folded and karstic area: the Jura Mountains. Three axes are developed:(1) Characterize the hydrogeological functioning of the Forbonnet peatland using geochemical tracers(δ18O, δ2H, 87Sr/86Sr, major ions);(2) Assess the links between hydrological and biogeochemical dynamics and their impact on inorganic carbon speciation (δ13CDIC);(3) Integrate the dynamics of greenhouse gas (GHG; CO2, CH4) fluxes at the scale of the ecosystem and at a finer scale (plot) according to the ecohydrological gradients inherent in these ecosystems.This work showed that the active peatland is a system fed in water by several components: directrainfall; lateral inflows from the surrounding wooded peatlands; and carbonated water fluxes supplying the deeper levels of peat. These carbonated waters flowed in the syncline, implying water and/or pressure transfers from the upstream anticline. This supply of carbonated water seems to favor the production of CH4 within the active peatland, while the downstream part of the system (rich fen and outlet) is not affected by this process. The net exchange of CH4 between the active peatland and the atmosphere ...