COMPARISON OF CARBON FLUXES BETWEEN DIFFERENT STAGES OF REGENERATION IN A HARVESTED BOG IN THE FRENCH JURA MOUNTAINS(ABSTRACT)

摘要

Sphagnum peat bogs have a large potential for peat accumulation because of a low rate of organic matter decomposition (1). At the present time, they represent a considerable stock of terrestrial carbon (2). Once harvested, a peat bog may become a carbon source, with both CO2 and CH4 losses. Their rehabilitation as a carbon sink is a considerable stake in the context of climate change, carbon sequestration and reduction of greenhouse gas emissions. It has already been shown that the re-establishment of specific bog vegetation - particularly the keystone Sphagnum moss- is essential for accumulating organic matter. The aim of this study was to determine biotic and abiotic conditions that favour the shift from a carbon source to a carbon sink. This study was conducted within the frame of the 5FPRTD project RECIPE (reconciling commercial exploitation of peat with biodiversity in peatland ecosystems).The study site is an harvested peat bog located in the Jura mountains. Three experimental plots were installed at differents stages of regeneration: bare peat, recent regeneration with Eriophorum angustifolium as dominant species and advanced regeneration with Sphagnum fallax as a dominant species. Open chamber coupled with an infra-red gas analyser (CIRAS1, PP systems, U.K.) were used to measure CO2 fluxes at weekly intervals on eleven 30cm-diameter collars. The CH4 fluxes were measured on the same collars with a closed chamber and a portable gas chromatograph (Micro-GC CP4900, Varian, U.S.A.). Climatic variables (air temperature, peat temperature at 5cm and 30cm depth, light intensity, rain fall events) were registered hourly. The depth of the water table and degree of Sphagnum dessication were recorded weekly. Vegetation diversity census was taken on one square meter around each ring and the leaf area index of vascular plants and mosses cover were followed during the growing season.Preliminary results showed that seasonal variations of temperature and Sphagnum dessication strongly influence the carbon balance of peat bogs. Daily variations of light intensity account for most of the daily variations of carbon exchange. Beyond these major factors, the importance of the type of vegetation appears also and, indeed, this has implication for the management when it comes to trigger the return of plant species. These data will be further used to parameterise a carbon balance model.