Recent experiments have shown that biodiversity loss can impair natural ecosystem functioning. Extraction of horticultural peat is known to alter the diversity of
vegetation and convert peatlands from net sinks to persistent sources of carbon to the atmosphere. Peatland restoration has been shown to reβestablish the natural
carbon sink function, however, current restoration techniques could be refined with more knowledge of the role of plant biodiversity. In a controlled field study, I tested the effect of plant biodiversity on carbon sequestration in an extracted peatland in Quebec, Canada. Closedβchamber method was used to measure the flux of carbon between the peatland and the atmosphere in fourteen treatments planted with different numbers of species. Species richness was not found to have a significant impact on carbon sequestration and no overyielding was detected in polycultures. Species identity was important with Carex aquatilis having a significantly positive impact on carbon sequestration