Summer droughts severely reduce forage yield in mountain grasslands. Subordinate plant species are often more drought-resistant than dominant species, potentially enhancing community resistance. The DryMount project tests whether integrating subordinate species into productive mixtures can sustain forage yield and quality under both optimal and drought conditions. Nine mixtures differing in dominant species identity and in the expected proportion of four subordinate species (0%, 15%, 30%) were established at four Swiss mountain sites with contrasting pedoclimatic conditions. The year after sowing, pPreliminary results show that higher subordinate species abundance led to lower forage yield in spring but higher forage yield in summer, whereas dominant species identity had no effect. These responses are mediated by shifts in community weighted mean functional traits (SLA and LDMC). Ongoing analyses will help identify the mechanisms driving the contribution of subordinate species to mixtures productivity and drought resistance and define optimal mixtures for sustainable forage production.