Recolonisation by Spontaneous Vegetation of a Rewetted Peatland after Topsoil Removal: a Focus on Biomass Production and Nutrient Uptake

The ability of spontaneous vegetation to recolonise a Mediterranean peatland was investigated to assess the combined effect of rewetting and topsoil removal on restoration of a drained area. The experiment tested the concept of converting the cultivated area into a constructed wetland system (CWS) of five cells. A mixed approach was used based on orthophotos from an unmanned aerial vehicle, phytosociological surveys, and destructive samplings performed during the fourth summer after the CWS set-up. Two spontaneous species dominated: Phragmites australis (Cav.) Trin. ex Steud. and Typha latifolia L.. Distance of the CWS from the inlet influenced the biomass yield of P. australis, which progressively decreased (from 7.81 to 3.87 kg/m2) and thus influenced other parameters, such as nitrogen (N) and phosphorus (P) uptake per unit area (from 153 to 74 g N/m2, from 13 to 7 g P/m2). Typha latifolia, with a mean production of 3.58 kg/m2 (in the last two (4th and 5th) CWS cells), took up 51 g N/m2 and 6 g P/m2. From these data, we determined that plants took up 1144 kg of N and 103 kg of P in their aboveground biomass and were able to store nearly 25% of the nutrient loads yearly