Abstract
Drought periods have been repeatedly observed in the last decade in the southern margin of the Alps. An adequate choice of drought-tolerant forage species and cultivars is of pivotal importance in tackling this challenge. Tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) are regarded as having contrasting levels of drought tolerance, but less is known about their intrinsic water use efficiency (Wi). To this end, analyses of the Carbon isotope composition of leaf material were performed on these species (one cultivar of perennial ryegrass, and two cultivars of tall fescue differing in leaf roughness) in the course of a field trial aiming at the optimization of seed mixtures for permanent meadows in drought-endangered areas under different management intensities and at two altitude ranges. Wi was found to be mainly affected by both genotype and altitude, with tall fescue showing higher Wi than perennial ryegrass.