Mechanisms and dynamics of Greenhouse Gas production and exchanges with atmosphere over peatlands. Combining geochemical, physical and sub-orbital remote sensing approaches

Despite covering only 3% of the global land surface, peatlands are an active part of the Critical Zone (CZ) exchanging large water and greenhouse gas (GHG) fluxes with the surrounding aquifers, surface waters, and the atmosphere. While ecosystem services of peatlands (carbon and water storage, buffering of local climate) are essential to address 21st century challenges regarding climate, biodiversity, and water resources, they are directly threatened by human activities at global (climate change) and local (drainage for agriculture, forestry and peat harvesting) scales. Understanding the hydrological, biogeochemical, and ecological mechanisms of peatlands functioning at different spatiotemporal scales is therefore fundamental to mitigate these impacts.

In order to characterize the mechanisms and factors controlling GHG sources, production and transfers in peatlands, an interdisciplinary field campaign took place at the Frasne peatland (7 ha, 46.826 N, 6.1754E, 840 m a.s.l), located in the Regional Natural Reserve of Frasne-Bouverans in June 2023. The site is a long-term observatory since 2008 and one of the four French peatland observatories (SNO Tourbières) of the French CZ research infrastructure (OZCAR). The peatland is also an observatory of the Zone Atelier of Arc Jurassien dedicated to exploring the interrelationships between human and nature.

During this campaign, a range of data was acquired, i.e. microbiological characterization (membrane lipid analysis to trace the involved microbial metabolisms), hydrogeochemical analyses of peat pore water (major elements, DOC (quantity and quality), dissolved CO2, CH4, δ 18OH2O-δ 2HH2O, δ 13CDIC, δ 13CDOC, δ 13CCH4, δ 2HCH4, δ 13CCO2) along upstream-downstream and surface-depth gradients. In parallel, GHG fluxes have been measured from the plot to the ecosystem scale, by combining dissolved gas profiles, chamber measurements, eddy-covariance and unmanned aerial vehicle characterization.

In order to propose a typology of the mechanisms and dynamics of GHG production in this system, the objectives of the internship will be :

• to map the GHG concentrations and fluxes over the system and combine these information’s with ecological data (vegetation, microtopography, water depth maps) ;
• to characterize the biogeochemical processes involved in the GHG production ;
• from the above-mentioned perspectives, to contribute to the organization of similar campaigns in other systems.

The candidate should have a formation in environmental sciences (hydrology, biogeochemistry, ecology, physico-chemistry of atmosphere, …) and a solid motivation for pluridisciplinary problematics. The detailed objectives of the work could be adapted regarding to the profile of the selected candidate. Basic knowledge in geographical information systems (e.g., QGIS), programming language (e.g., R, Python), and good communication skills are recommended.

Mis à jour le 22 novembre 2023