Restoration of sub-alpine shrub-encroached grasslands through pastoral practices: effects on vegetation structure and botanical composition

Aims: To reverse shrub encroachment and restore grassland vegetation, two pastoral practices were implemented over shrub-encroached areas: the arrangement of temporary night camp areas (TNCA) and the strategic placement of mineral mix supplements (MMS) for cattle. The aim was to assess the effects produced on (1) vegetation structure and (2) botanical composition of both pastoral practices in order to identify their potential to reverse shrub encroachment and restore semi-natural grassland vegetation. Location: Shrub-encroached sites in Val Troncea Natural Park, southwest Italian Alps. Methods: We measured the effects produced by both practices on vegetation cover and height, cover of species belonging to different vegetation units, biodiversity indices (species richness and Shannon diversity index), forage pastoral value, and average indicator value for soil nutrient content from 2011 to 2014 along permanent linear transects. Data were analysed with GLMMs, multiple response permutational procedure (MRPP) and principal response curve (PRC). Results: Both practices were effective in reducing shrub cover and increasing average height of the herbaceous layer, but within TNCA a marked increase in herbaceous cover was also evident. Moreover, the arrangement of TNCA increased the cover of meso-eutrophic grassland and fringe and tall herb species and decreased the cover of boreal-like shrubland and woodland species. The main effect produced by the placement of MMS on botanical composition was an increase in cover of fringe and tall herb species. Plant biodiversity was enhanced by the arrangement of TNCA but not by the placement of MMS, and the implementation of both practices increased forage pastoral value and average indicator value for soil nutrient content. Conclusions: The arrangement of TNCA was the most effective pastoral practice to reverse shrub encroachment, restore semi-natural meso-eutrophic grassland vegetation and increase plant diversity, herbage mass and forage quality.