CRITICAL PEAT project : The importance of hydrology for Carbon Reactivity along with atmosphere - peatland interactions. Preliminary results from the Frasne peatland monitoring (Jura Mountains, France).

Abstract : In the framework of climate changes, peatland ecosystems are compartments of the Critical Zone of growing importance for greenhouse gas (GHG) exchanges with the atmosphere. Peatlands contain about 30 % of the total organic soil carbon worldwide. Interactions of GHG between atmosphere and peatland are potentially controlled by organic matter production and degradation controlled by biotic functiuns, which are in turn influenced by diverse abiotic factors including (1) water saturation, (2) peat humification degree, and (3) water quality conditioning electron acceptor availability. Delineating the detailed roles of these mechanisms is therefore challenging for long-term peatland management, requiring a detailed spatio-temporal monitoring of a wide range of hydrological and biogeochemical parameters. The Frasne peatland (Jura mountains, eastern France), belonging to a regional natural reserve is an outstanding site for such studies as it is monitored since 2008 in the framework of the national observatory of peatlands (SNO Tourbières),and belongs to the Zones Ateliers (RZA) and French Critical Zone (OZCAR) networks supplying the Europe Long-Term Ecosystem Research (eLTER) database (DEIMS-SDR). The peatland took place in a periglacial context on groundmoraines covering a large-scale karstified synclinal structure. This complex geological setting is combined with eco-physical (peat thicknesses and maturity), and hydrological (water-table depth) heterogeneities at the peatland scale. Based on daily hydrometeorological data (P, T, potential evapotranspiration, groundwater level) and monthly monitoring (hydrochemistry; peat lability, GHG fluxes) in 25 piezometers, the goal of the CRITICAL PEAT project is to identify the hydrological and biogeochemical drivers controlling GHG exchanges between peatland and atmosphere. In this perspective, this contribution aims at presenting preliminary results on the hydroclimatic sensitivity of the system inferred from correlation analyses, and its relationships with water origin and chemistry.