Effects of ecological restoration on beetle assemblages: results from a large-scale experiment in a Mediterranean steppe rangeland

Given that biological conservation cannot prevent the full range of negative impacts on biodiversity, ecological restoration is nowadays commonly acknowledged as a necessary tool for conservation purposes. Here, we report on an ecological rehabilitation project in the La Crau area (south-eastern France), beginning in 2009 when a former industrial orchard (357 ha) was rehabilitated into a Mediterranean rangeland. We assessed the effect of ecological rehabilitation and different additional restoration treatments on beetle assemblages. Seven treatments were considered: the reference steppe, the rehabilitated treatment alone, three additional experimental restoration treatments (soil transfer; nurse species seeding and hay transfer), the control and the edge between the steppe and the former industrial orchard area. All beetle families were considered. Beetles were sampled with pitfall traps for 3 years (2011–2013). Our major finding was a positive effect of soil transfer and nurse species seeding treatments, which promote the characteristic beetle composition of the reference steppe. Nevertheless, strong differences remain between the steppe and the various assessed treatments in terms of composition. Long-term monitoring should therefore now focus on particular beetle indicator species that could reflect the response of the overall characteristic beetle assemblage of the reference steppe.