Large-scale heterogeneous cattle grazing affects plant diversity and forage value of Alpine species-rich Nardus pastures

In Europe, the decline in agriculture in traditional mountain farming areas has caused abandonment, or irregular grazing, of less accessible pastures. In the Italian Alps, we studied plant diversity, forage value and trophic traits in six large-scale heterogeneously grazed Nardus pastures, in their central and peripheral parts, and across the montane, lower and upper subalpine zones. Seventy cover-abundance floristic releves were performed in randomly located permanent plots, half at the pasture edge (M-plots) and half in their central part (C-plots). Plant diversity varied significantly with respect to the distance from the edge, being higher in M-plots because of shrub invasion as a consequence of reduced cattle pressure. Nardus cover was slightly higher in C-plots and negatively related to plant diversity. Forage value was lower in M-plots and negatively correlated with the cover of Nardus and woody species, implying that different grazing pressure was negatively influencing sward productivity. Differences in trophic traits of swards between C- and M-plots existed mostly as trends. Forage value significantly decreased in the lower subalpine and montane pastures, which are further grazed in late summer. Heterogeneous grazing management was therefore exerting positive effects on plant diversity and negative effects on forage value. Results are discussed in the context of future management recommendations.