Rewetting is not enough: Sphagnum transplants promote lowering of greenhouse‐gas emissions in peatlands

Introduction Degraded peatlands contribute up to 2 gigatons CO 2 ‐equivalent annually (approximately 5% of anthropogenic greenhouse gas emissions). As restoration efforts increase, the effectiveness of combined hydrological and vegetation restoration strategies remains insufficiently understood. Objectives This study investigates the short‐term impacts of rewetting, topsoil removal, and Sphagnum transplantation on carbon fluxes and greenhouse gas carbon balance in La Guette peatland in France, a disturbed temperate peatland invaded by Molinia caerulea . Methods Carbon dioxide and methane fluxes, vegetation, and environmental variables were monitored between 2014 and 2017 at La Guette peatland, across Control (unchanged), Bare (top‐soil removed), and Sphagnum (top‐soil removed + Sphagnum transplants) plots within rewetted and non‐rewetted subsites. Empirical models for ecosystem respiration, gross primary production, and methane fluxes were used to estimate annual carbon budgets, considering only ecosystem–atmosphere exchanges (excluding the carbon physically lost through topsoil stripping). Results Rewetting elevated the water table by approximately 7 cm and slightly reduced carbon emissions (by approximately 124 gCO 2 ‐eq m −2 yr −1 ) when implemented alone. Control plots showed the highest emissions. Top‐soil removal lowered emissions, and when coupled with Sphagnum reintroduction in rewetted areas, achieved the greatest greenhouse gas mitigation. Methane emissions increased post‐rewetting, but this increase remained outweighed by reductions in carbon dioxide emissions. One Sphagnum ‐restored plot approached carbon neutrality within the third year. Conclusions Although restored plots remained net carbon sources, combined hydrological and vegetation interventions significantly limited carbon losses and CO 2 ‐equivalent emissions compared to degraded conditions. Restoration thus prevents further carbon stock deterioration in disturbed peatlands while reducing climate impacts.