Environmental factors and management intensity affect in different ways plant diversity and pastoral value of alpine pastures

Based on a wide dataset of vegetation surveys carried out across the pastures of Western Italian Alps, the objective of the research was to determine the relative importance of management intensity and environmental factors (i.e. topography, climate, bedrock type) on 1) plant diversity and 2) forage quality and productivity (Pastoral Value - PV) of alpine summer pastures. Plant diversity (i.e. Shannon diversity index and species richness) and PV were affected in different ways by both factors, but they showed a hump-shaped relationship with pastoral management intensity. Plant diversity was mainly affected by environmental factors (elevation and total annual precipitation) rather than management intensity. Shannon index and species richness were lower at higher elevations and in locations with higher precipitation, and they were higher on steep sites and calcareous bedrock. However, management intensity had a noteworthy influence on plant diversity. PV was strongly affected by management intensity, whereas environmental factors had limited importance. Differently from plant diversity, PV was not elevation dependent as several vegetation communities with either a low and a high PV occurred within a large range of altitude. PV was higher on flattest sites, in sites with a low level of precipitation, and on calcareous bedrock. Our results highlighted that environmental factors are the main drivers of plant diversity in alpine pastures. Pastures are typically located at higher elevation, are less accessible, and lay in less homogeneous areas where the environmental constraints have a predominant effect on plant community development with respect to management intensity. Contrariwise, the influence of management intensity on PV suggests that an appropriate grazing management can enhance forage productivity and quality for livestock even in harsh environments.