Hydro-ecological controls on dissolved organic matter production, mineralization into greenhouse gases, and export in a temperate peatland: the Frasne case study, Jura mountains, France.

Peatlands can be viewed as a nexus of water, organic material, and specific biodiversity, allowing long-term (millennial-scale) storage of significant volumes of carbon. Spatial or temporal modification of one of the three pillars of this nexus may alter the capacity of peatlands to retain carbon in the soil and promote the production of greenhouse gases such as CO₂ and CH₄. This study illustrates these relationships by analyzing atmospheric CO₂/CH₄ concentration variations measured using an Unmanned Aerial Vehicle over the 7 ha Frasne peatland (Jura Mountains, France), which is part of the French Observatory of Peatlands (SNO Tourbières). These data were compared with vegetation and topographic characteristics, as well as hydrogeochemical information (Dissolved Organic Carbon-DOC, Fluorescence Index-FI, Biological Index-BIX, aromaticity, δ¹³C-DOC) from pore waters sampled across a network of piezometers throughout the ecosystem. Preliminary results suggest a multiscale control of potential GHG emissions. At the ecosystem scale, we observe a positive relationship between [CO₂] and [CH₄], which appears to reflect a general upstream–downstream gradient in peat surface elevation and vegetation type. The indicators of pore water DOC quality ((aromaticity, FI, BIX) also present upstream-downstream gradient suggesting molecules of lower weight and greater microbial activities origin in the downstream where atmospheric greenhouse gases concentrations were the highest. At a more local scale, CH₄ and CO₂ concentrations are anticorrelated, suggesting a dominant influence of water-table depth and the content and quality of pore water DOC. These findings highlight the importance of considering both spatial scale and hydroecological conditions when assessing GHG dynamics over peatlands. Continued integration of UAV-based gas monitoring with field-based geochemical and ecological data offers a promising approach for improving our understanding of the complex feedbacks driving peatland carbon emissions.