Plant diversity and pastoral value in alpine pastures are maximized at different nutrient indicator values

Plant diversity, PV, and N values were higher in the pastures located at lower elevation. Plant diversity and PV showed a unimodal relation with N values, both in the montane/sub-alpine and alpine belts. Plant diversity indexes peaked at intermediate N indicator values, confirming the Intermediate Disturbance Hypothesis, while PV peaked at higher N values, where higher nutrient availability in the soil increased plant species productivity, growth rate, leaf turnover and nutrient concentration, digestibility, and palatability. The overall shape of the curves as well as the N values at which plant diversity and PV values peaked did not considerably change from montane/sub-alpine to alpine pastures. These results suggest that an extensive pastoral management is recommended when plant diversity conservation is the main goal. Conversely, a more intensive management can produce an overall enhancement of forage quality/productivity of alpine pastures, but only if restricted under certain critical N values.