Pastoral practices for the restoration of sub-alpine open habitats: short-term effects on vegetation and dung beetles.

Throughout the last decades, pastoral abandonment has produced deep landscape and ecological changes in the Western Italian Alps. In particular, the reduction of grazing has led to an extensive tree and shrub-encroachment of sub-alpine semi-natural grasslands, which represents a threat to alpine biodiversity, as the preservation of many plant and animal species is strongly dependent on the maintenance of these open habitats. In this study, two different pastoral practices were performed to restore shrub-encroached open habitats and short-term effects on vegetation and key ecological groups, the dung beetles, were assessed. The practices were the strategic placement of mineral mix supplements (MMS) to attract cattle into traditionally underused areas and the arrangement of temporary night camp areas (TNCA) over shrub-encroached vegetation patches. Practices were carried out during the summer 2011 in eight treatment sites (4 MMS and 4 TNCA) and for each treatment site a paired control site was identified. Vegetation surveys using vertical point-quadrat method and sward stick method and dung beetle sampling using dung baited pitfall traps were performed during the summer 2011 and 2012. In 2012, a reduction in shrub cover and an increase in bare ground cover around MMS sites were detected. A more intense restoration effect was detected within TNCA, as an increase in forage pastoral value, cover and height of the herbaceous layer were also detected. Immediately after treatment, changes in dung beetle diversity (total abundance, species richness, Shannon diversity, taxonomic and functional diversity) showed a limited disturbance effect caused by restoration practices. In contrast, the effect on dung beetles reversed one year later, changing from slightly detrimental to beneficial. Both at MMS and TNCA sites, dung beetle diversity significantly increased. Moreover, Multivariate Regression Trees analysis and associated Indicator Value showed that some ecologically relevant dung beetle species preferred areas deprived of shrub vegetation. Consequently, we suggest that the increase of open habitats can produce an increase in dung beetle diversity and that dung beetle community may positively influence the restoration of grassland vegetation with a “backward feedback”. Both MMS and TNCA appear to be sustainable practices for the restoration of open habitats, as they are low cost and they can be easily carried out on rugged alpine locations. Short-term effects produced are worth of mention in a framework of ecosystem functionality, considering that dung beetles are one of the main mediators of nutrient redistribution in soil and are therefore responsible for the ecosystem functions of sub-alpine grasslands.