Plant species selection by sheep in semi-natural dry grasslands extensively grazed in the south-western Italian Alps

Abstract

Sheep can have an important role in the conservation of abandoned and shrub- and tree-encroached, semi-natural dry grasslands because their feeding behaviour is known to affect plant diversity and structure. Nevertheless, little information is available about feeding preferences of sheep at the sward-patch scale and about the effects of stocking density on their selectivity. Consequently, we investigated plant-species selection by sheep managed with a low-intensity grazing, examining the influence of stocking density and plant species abundance by means of vegetation surveys and animal GPS tracking. Sheep grazed a graminoid-dominated, semi-natural dry grassland (Festuco–Brometea) in Piedmont Region, north-west Italy. Plant species, classified into graminoids, suffruticose forbs, and herbaceous forbs, were selected with a different intensity by sheep, which preferred graminoids over suffruticose and herbaceous forbs. Plant species showing a high consumption ratio (CR), i.e. the level of selection of plant species (CR >10%), were mostly graminoids (e.g. Bromus erectus, Koeleria vallesiana and Stipa pennata). Furthermore, Carex species were also noticeably selected, in particular C. humilis, whereas spiny species and those with a rosette or prostrate forms were rarely grazed. The heterogeneity of stocking density over the pasture allowed testing of the relationships between stocking density and CR. For many species, the higher the stocking density, the higher was the CR, regardless of the abundance of dominant neighbouring species. Results suggest that sheep under low-intensity grazing conditions exert a specific plant-species selection in abandoned dry grasslands. By regulating the stocking density through the management of grazing sheep, it may be possible to condition the consumption of certain plant species, with medium–long-term effects on the botanical composition.