Multivariate analysis of the response of overgrown semi-natural calcareous grasslands to restorative shrub cutting

Monitoring and evaluation of restoration management often suffers from poor sampling design and a lack of statistical rigour, seldom considering the spatial and temporal variability of habitat. We tested the effectiveness of shrub cutting on the restoration of calcareous grasslands, using a 4-year Before–After/Reference-Control-Impact (BARCI) project design with replicated patches of habitat. Departure from the control sites and convergence with the reference sites were analysed using the Principal Response Curves (PRC) method. The structure of communities was compared 1 year before and 3 years after management on control scrubland, restored ex-arable land, restored and reference grassland. Results show that shrub cutting did not suffice to restore the community composition of the semi-natural calcareous grasslands. The restored ex-arable areas maintained a community structure extremely similar to the control scrubland. The restored grassland, on the other hand, deviated from the control and slightly converged to the reference grassland, though not significantly. The dominant scrub species that was cut, Prunus spinosa, showed higher cover values compared to the reference grassland in any of the treatments, even the first year after cutting. Species typical of xeric and/or calcareous grassland were more abundant in the reference than in the restored grassland, while arable and ruderal species were more frequent in the restored sites. This study has demonstrated that the BARCI approach is a powerful tool for the evaluation of restoration management, as it was possible to evaluate not onlydeparture from the unmanaged control, but also convergence with the reference community. The PRC method provided a comprehensive overview of the response of the 153 species involved in the study. Our results also indicate that the second PRC should be considered, when significant, to not exclude important information from the assessment.