How ecologically similar is the vegetation of a restored Sphagnum-dominated peatland from that of a natural bog? A comparative approach with reference ecosystem

Since its conception in the late LSQUO90s, the moss layer transfer technique (MLTT) has been applied to restore several Sphagnum-dominated peatlands (bogs) formerly extracted for horticultural peat across Canada (~2000 ha). Indeed, this ecological restoration method allows restoring not only the hydrological conditions characterized by a high water table, but also the vegetation typical of bogs mainly represented by a Sphagnum carpet and ericaceous species. Thus, the purpose of this study is to assess, from a moss cover perspective, specifically from Sphagnum sp. and Polytrichum strictum, the similarity or ecological distance of restored Canadian Sphagnum peatlands in comparison with a reference ecosystem represented by a set of natural bogs. Several vegetation inventories have been conducted over the past 25 years on permanent plots installed in Canadian restored peatlands. In this study, we analyze a subset of these permanent plots (n=654) in two Canadian provinces (Quebec and New Brunswick) to study the succession dynamics of post-restoration moss layer. In addition, other inventories have been carried out in natural reference peatlands to allows for comparison. The results show that the cover of Sphagnum mosses exhibits an increase over time (0-20 years post-restoration), reaching, for some older sites, a mean cover of 43±7% in the surveyed plots (natural bogs: 84±1%). A first increase followed by a decline in the cover of Polytrichum strictum over a period of 10 years has also been observed, and could underline its importance as a nursing plant facilitating Sphagnum colonization. The successional trajectory of restored peatlands predicts that a similar Sphagnum cover could be achieved in around 30-40 years provided that the relation between time and the increase in Sphagnum cover remains linear.