Effects of ecological restoration on Orthoptera assemblages in a Mediterranean steppe rangeland
Résumé
In the last century, human activities have contributed to the fragmentation and the loss of 80 % of the original surface of a Mediterranean steppe rangeland in southeastern France. In a recent ecological restoration project, an intensively cultivated orchard of 357 ha planted in 1987 among the steppe vegetation was rehabilitated as a herbaceous habitat for steppe birds after its abandonment in 2006. In addition, three experimental restoration treatments (nurse species seeding, hay transfer; soil transfer) were applied at large scale to test the restoration of the original steppe vegetation. Our four-year study aimed to assess the effect of this rehabilitation and the restoration treatments on Orthoptera assemblages. Capturing the Orthoptera with sweep nets, we measured species richness, abundance, Shannon index, Shannon evenness, Renkonen similarity index and two community structure indices. Our results reveal no significant differences in Orthoptera species richness, abundance and diversity between control and reference steppe after 4 years, indicating that the rehabilitation and the three restoration treatments did not significantly accelerate natural recolonization. In the last year of survey, Orthoptera abundances were still significantly lower in the restored treatments than in the original steppe. Thus, future monitoring will need to determine whether abundance and structure similar to that of the reference steppe is achieved in these restored treatments.