Carabid beetles and spiders as bioindicators for the evaluation of montane heathland restoration on former spruce forests

Semi-natural habitats such as heathland ecosystems are important for the conservation of biodiversity. Due to land use changes, these valuable ecosystems have become highly threatened. Nowadays, their management and restoration is of special relevance for nature conservation.In this study, we used carabid beetles and spiders as bioindicators to evaluate the success of montane heathland restoration on former spruce forests. We compared three different treatments: (i) montane heathlands (MONHEATH), (ii) restoration (RESSITE) and (iii) control (CONTROL) sites.Four to five years after conducting the restoration measures, all environmental variables, except soil moisture, significantly differed between MONHEATH on one hand and RESSITE and CONTROL on the other. MONHEATH was characterised by a high cover of dwarf shrubs; in contrast, RESSITE/CONTROL had a vegetation rich in herbs/grasses with some bare ground. Both carabid beetle and spider assemblage composition clearly reflected these differences in environmental conditions. Alpha-diversity (Simpson diversity, evenness) and niche positions were, however, only significantly different for spiders. Diversity as well as spider indicator values for shade and moisture were higher for MONHEATH.Due to the cool and wet montane climate and the dense dwarf-shrub stands the carabid beetle and spider species characteristic of MONHEATH are typical woodland species. Four to five years after restoration, RESSITE and CONTROL still represent early successional stages with a low cover of the Ericaceae target dwarf shrubs (Calluna vulgaris, Vaccinium myrtillus and Vaccinium vitis-idaea), but are already home to some typical heathland carabid beetle and spider species that are missing in MONHEATH.