Julie Chenot

Consequences of iceplant (Carpobrotus) invasion on the vegetation and seed bank structure on a Mediterranean island: response elements for their local eradication

Abstract Biological invasions are one of the world’s leading causes of biodiversity loss. Islands are particularly good models for studying the impact of invasive species. Bagaud island (58 ha), which is part of Port-Cros National Park (southeastern France), is currently suffering an invasion of Carpobrotus. A restoration project has been established with the aim of eradicating these species to protect native ecosystems. The objective of the present study was to examine the plant composition of the local vegetation and seed bank (in litter and soil) focusing on (i) Carpobrotus patches and (ii) native plant communities, with the ultimate goal of determining whether Carpobrotus removal is followed by native plant community colonization. A further objective of this study was to help identify the most effective protocol for adequate ecological restoration. Native plant communities found around Carpobrotus patches can vary depending on whether the patch is located on the coast or inland; we can therefore expect a variety of plant communities to form following Carpobrotus removal. Even though Carpobrotus litter can frequently contain seeds of native species, such Atriplex prostrata, Frankenia sp. and Sonchus asper, it also contained many more Carpobrotus seeds (77.6%). Therefore, it is important to remove Carpobrotus litter to prevent large numbers of Carpobrotus seeds from recolonizing after eradication. We conclude that the most effective ecological restoration protocol consists of the following: (i) the removal of living Carpobrotus plants and (ii) the removal of Carpobrotus litter. This protocol can be made even more effective by following it up in the near and mid-term by periodic and thorough checks for Carpobrotus reinvasion.

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.