Revegetation dynamics after 15 years of rewetting in two extracted peatlands in Sweden

Abstract

The restoration of extracted peatlands poses challenges with regard to their recolonisation by vegetation. The most significant problems are unstable water levels, destroyed propagule bank, and temperature fluctuations on bare peat surfaces. Rewetting is considered necessary for the re-establishment of peat-forming vegetation. Revegetation was investigated in a long-term field study at two rewetted extracted peatland sites in south-central Sweden, namely Västkärr (originally a lagg fen) and Porla (originally a bog). Both sites were expanses of bare peat before rewetting. Rewetting procedures were applied in 1999 and strongly promoted plant colonisation. At Västkärr, colonisation started in the first year after rewetting, mostly by species that were not found during repeat vegetation surveys 15 years later. By 2014, Västkärr was a shallow lake surrounded by mesotrophic and eutrophic vegetation with species such as Carex rostrata, Lemna minor, Typha latifolia, Phalaris arundinacea and Phragmites australis. Revegetation of the Porla site was slower and started with Eriophorum vaginatum and Polytrichum spp. Sphagnum mosses appeared after six years and had established quite well after 13 years. A residual Sphagnum peat layer, inflowing surface water and groundwater provided spatially variable nutrient conditions. Sphagnum species and E. vaginatum established in nutrient-poor areas, while C. rostrata, P. australis and Eriophorum angustifolium colonised more nutrient-rich locations.

Keywords

• biodiversity
• hydrology
• nutrient status
• re-vegetation
• water chemistry