Abstract
Grass species are expected to show a species-speciic response to drought. Two seed mixtures, containing grass species in diierent proportions, were investigated in a four-year eld experiment at two drought-endangered sites: 835 m a.s.l. (low altitude) and 1,205 m a.s.l. (high altitude). ree cutting frequencies (2, 3 or 4 cuts year-1) coupled with increasing fertilization rates (equivalent to 1, 1.4 or 2 livestock units ha-1) were applied. Just before the rst cut, the yield proportion of each species was assessed. Drought indices, based on cumulated precipitation and evapotranspiration, were computed for each regrowth based on meteorological data and the eeect of drought was explored. e eeect of drought on the yield proportion of the sown grasses was quantiied by means of mixed models accounting for design eeects, the abovementioned factors and the cumulated water stress (CWS), for both the growth period until the rst cut and the growth period corresponding to the last regrowth of the previous growing season. All species were aaected by CWS. As expected, Arrhenatherum elatius and Festuca arundinacea increased their yield proportion under high water stress. e opposite was observed for Lolium perenne, whilst a less clear response was obtained for the remaining grass species.