No other species can replace them: evidence for the key role of dominants in an alpine Festuca varia grassland

Questions Festuca varia grasslands occupy extensive areas in the alpine belt of the Caucasus. In the Teberda Reserve the dominant, narrow‐leaved grasses Festuca varia and Nardus stricta contribute up to 56% and 22%, respectively, to the total biomass of the community. How does community composition and structure change after removal of the dominant, and is any species able to replace dominants in abundance and function? Location Teberda State Biosphere Reserve, northwestern Caucasus, Russia. Methods We experimentally removed F. varia and N. stricta (as single dominants and both together). After 20 yr of treatment we compared the expected increase in species richness per plot, above‐ground phytomass, community biomass‐weighted mean SLA and leaf DMC, as well as the inter‐annual dynamics of functional groups and the most abundant species. Results Dominant removal led to a decrease in litter after removal of F. varia and of both dominants, and a decrease in total phytomass after removal of both dominants. Biomass of dominants did not respond to the treatments, however N. stricta increased shoot number after F. varia removal. Non‐dominant narrow‐leaved grasses increased in all the treatments, both in biomass and shoot number. Community biomass‐weighted SLA increased in all the treatments, and leaf DMC decreased. Conclusions Dominants play a key role in alpine F. varia grasslands and determine the functional structure and composition of the community. Species from other functional groups and, remarkably, species from the same group, are not able to completely replace them. Traits of F. varia, as the main dominant, control community‐weighted leaf traits and litter accumulation.