Plant communities of a coastal lagoon foredune: definition of the reference and restoration after compaction

Abstract Throughout the world, dunes are being altered by human activities. Dunes can be restored to naturally functioning systems to protect human settlements and coastal strips and preserve biotopes. This study took place on the Jaï dunes, on the shore of a coastal lagoon in southeastern France, which were mainly degraded by vehicles. The objectives of this work were (1) to define the reference ecosystem by gathering historical information and exploring other regional sand dunes; (2) to find out about the restoration potential of the site by studying the degraded seed bank; (3) to test the efficacy of a few basic restoration actions. Historical information was of little help in defining the reference ecosystem. The description of EU Habitat Directive habitat types and the selection of regionally less degraded sites allowed us to compile the following list of plant species that we could expect to find in the restored area: Anthemis maritima, Elytrigia juncea, Glaucium flavum and Sporobolus pungens. The seed bank of the road was mainly composed of Juncus acutus, which is not a typical dune species and therefore did not have much potential for restoration. Ploughing can therefore be used to decompact the sand road without hampering colonization from the seed bank. Ploughing was only efficient when the following other conditions were met: environmental conditions adequate for the establishment of dune vegetation, and a sufficient connection between the beach, the foredune and the restored area.