Restoration of a cirsio-Molinietum fen meadow on an agriculturally improved pasture

Abstract

The objective of this study was to identify soil nutrient availability conditions that would allow the establishment of key species of the Molinia caerulea-Cirsium dissectum fen meadow. The restoration site was a species-poor agriculturally improved pasture that had received no inorganic fertilizer for greater than 13 years. Treatments designed to reduce site fertility included: cutting and removal of herbage, cultivation, fallowing and topsoil removal. Straw and/or ligniticclay were incorporated as soil amendment treatments. Cirsio-Molinietum species were either sown or planted as seedlings on treated plots. Neither soil nitrogen nor potassium availability, per se, appeared to limit the establishment of Cirsio-Molinietum species, whereas enhanced phosphorus availability did. Removal of the top 15-20 cm of soil reduced the total soil phosphorus amount by about 85 percent and depleted plant P availability. Nutrient-poor and relatively calcium-enriched soil exposed by topsoil removal allowed the development of a community with affinities to the Cirsio-Molinietum typical fen meadow. Redundancy analysis indicated the existence of marked vegetational gradients within the topsoil removal treatments that were influenced by the straw and the lignitic-clay amendments. The way in which these two amendments influenced edaphic conditions were unclear. Where the topsoil was not removed the vegetation became dominated by a few competitive species and although many of the planted Cirsio-Molinietum species were still present after four years, they were found only in trace amounts. Removal of most of the soil organic matter was a practical success in that in created suitable edaphic conditions for all the planted Cirsio-Molinietum species to remain well established.