(Not) sweeping invasive alien plants under the carpet: results from the use of mulching sheets for the control of invasive Carpobrotus spp.

Abstract

Biological invasions represent a global threat to biodiversity. Particular attention should be made to the management of alien plants. The species from the Carpobrotus genus are well-known invasive plants native to South Africa, whose detrimental effects on native communities are widely documented. These impacts have become particularly important in terms of their invasive potential on small Mediterranean islands, where they often threaten particular ecosystems and endemic species. We report the experience from the efforts to eradicate this species from the island of Giannutri (Tuscan Archipelago, Italy)—an action included within the EU LIFE project “RESTO CON LIFE”—where the species occurred on about 14,000 m2 of coastal vegetation. The eradication employed an integrated approach with two control methods (manual removal and covering with mulching sheets) and involved mosaic rocky cliff coastal vegetation and disturbed areas with loose soil close to the cliffs. We present here the results obtained from five years of monitoring using permanent plots. Carpobrotus spp. exerted strong impacts on the invaded plant communities, with significant depletion and replacement of native species. Both of the control methods proved effective in the suppression of the mat formed by the invasive species and led to a positive response of native vegetation. Nevertheless, the recovery of native plant communities differed depending on the type of substratum, taking longer on rocky cliffs due to the harsher conditions. Improvements were driven by nitrophilous species in the plots treated with mulching sheets.