Effect of hydrological and vegetation restorations on the C sink function of the disturbed La Guette peatland.

Natural peatlands represent 1/3 of the world C soils and contribute significantly to sequestration of atmospheric CO₂ by assimilation and storage of non-well decomposed organic C, due to their specific predominant vegetation such as Sphagnum species. However, they are encountering anthropogenic-induced pressures that disturb their structure (implying shift of vegetation), with potential consequences on their carbon sink function. In an attempt to mitigate this effect, restoration experiments were undertaken at La Guette peatland, a hydrologically disturbed temperate Sphagnum-peatland invaded by vascular plants, which is now a carbon source. Hydrological restoration was performed by blocking drains with dams and vegetation restoration was undertaken by either i) removing first 5 cm of peat (bare plots) or ii) removing first 5 cm of peat and transferring Sphagnum mosses (Sphagnum plots). To study the effect of these experiments, CO₂ and CH₄ fluxes together with environmental variables and vegetation indices were monitored from 2014 to 2017 in 24 2mx2m plots. The annual carbon budget for each plot was estimated using empirical models. Preliminary results show that the hydrological restored site presented lower annual mean CO₂ emissions than the undisturbed site. In addition, Sphagnum plots had the lowest annual mean CO₂ emissions followed by bare peat plots then by intact plots. Hence, the results of these models provide evidence that hydrological and vegetation restorations favour the return to the C sink function of the peatland. However, there is still a need for larger-scale studies to better estimate the effect of restoration activities on peatland greenhouse carbon budgets.