Distribution of potential CO2 and CH4 productions, denitrification and microbial biomass C and N in the profileof a restored peatland in Brittany (France)

The aim of the work was to assess the progress of regeneration in the Landemarais peatland (Brittany, France), 8 years after the restoration of hydrological conditions. Peat C/N ratio ranged from 36 in the surface layers to 16 at 160 cm depth. The distribution of microbial activity with depth showed a decreasing CO2 and increasing CH4 productions, from the surface to 160 cm depth. Values for CO2 ranged from 26 ± 2 to 185 ± 34 μg C•g–1 dry peat•d–1. For CH4, values increased from 0 to 4 ± 2 μg C•g–1•d–1. No significant denitrification was detected during the experiment. Microbial biomass C and N ranged from 1.7 ± 0.1 to 4.2 ± 0.3 mg C•g–1 and from 352 ± 38 μg N•g–1 to 276 ± 35 μg N•g–1 respectively. The microbial activity profile analysis showed: (i) a restoration process but a quantitative C balance always favourable to a ‘source’ functioning; (ii) an interface at 75 cm depth which could correspond to the average depth of the water level before the restoration of hydrological conditions. The shift between microbial and vegetation community (recolonisation of turfigenous plants) responses could inform us on the speed of recovery of peat accumulation and give information about time resilience, i.e. the capacity of the system to accumulate peat.