Population structure of three dominant sedges under Muskox herbivory in the High Arctic

We investigated population structure of Carer aquatilis ssp. stans, Carer m embranacea, and Eriophorum angustifolium ssp. triste in ungrazed and grazed (by muskoxen) high arctic sedge meadow vegetation. Age structure, density, biomass, growth, and reproduction of tillers were compared between sites i n 1995 and 1996. Tillers were considerably older in ungrazed vegetation rel ative to grazed vegetation. The density and biomass of C. stans were signif icantly greater in grazed vegetation than in ungrazed vegetation, whereas t he density of C. membranacea and E. triste was the same but the biomass was lower relative to the ungrazed meadows. The grazed plants of all species r eproduced earlier, but no seedlings were found in grazed vegetation, in con trast to ungrazed vegetation. Carer stans appears to gain competitive advan tage over the other two species in grazed vegetation. This may be due to th e larger belowground biomass, the high phenotypic plasticity in rhizome len gths and more persistent rhizome connections. E. triste may be the least bu ffered against grazing due to its lower belowground biomass and the early d isintegration of rhizomes. On the other hand, E. triste allocates more to s exual reproduction than the two other species.