Rejuvenation and restoration measures foster specialised and threatened carabid beetle species in montane heathland ecosystems

Abstract

Montane heathlands are among the most threatened semi-natural ecosystems across Central Europe. Nevertheless, empirical studies on the effects of rejuvenation and restoration of montane heathlands have been scarce thus far. The aim of our study was to analyse the long-term effects of heathland rejuvenation and restoration on carabid beetle assemblages. Our study took place in the Rothaar Mountains, one of the most important strongholds of montane heathlands in Central Europe. We considered four different successional stages: (i) early-successional heathlands as a result of rejuvenation measures (EARLY), (ii) restored heathlands (RESTORED), (iii) late-successional heathlands (LATE) and (iv) windthrows (WIND). Our study revealed that the composition of carabid beetle assemblages differed across the gradient. From the earlier to the later stages, beetle biomass, richness of macropterous, threatened and heathland species decreased, whereas moisture and shading indicator values increased. The number of indicator species peaked in EARLY and RESTORED. Solely brachypterous species had the highest species richness in the later seral stages. Overall, rejuvenation and restoration measures fostered specialised and threatened carabid beetle species of montane heathlands. In contrast, carabid beetle assemblages of the two later and dense successional stages consisted mainly of non-threatened habitat generalists. Vegetation structure and the interrelated microclimate are assumed to be the key drivers of assemblage composition. For the long-term conservation of montane heathlands and their specialised carabid beetle assemblages, we recommend rejuvenation by sod cutting and choppering in a mosaic-like manner and at intervals that clearly exceed more than two decades.