Population Structure of Three Dominant Sedges under Muskox Herbivory in the High Arctic

Abstract

We investigated population structure of Carex aquatilis ssp. stans, Carex membranacea, 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 in 1995 and 1996. Tillers were considerably older in ungrazed vegetation relative to grazed vegetation. The density and biomass of C. stans were significantly greater in grazed vegetation than in ungrazed vegetation, whereas the 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 reproduced earlier, but no seedlings were found in grazed vegetation, in contrast to ungrazed vegetation. Carex stans appears to gain competitive advantage over the other two species in grazed vegetation. This may be due to the larger belowground biomass, the high phenotypic plasticity in rhizome lengths and more persistent rhizome connections. E. triste may be the least buffered against grazing due to its lower belowground biomass and the early disintegration of rhizomes. On the other hand, E. triste allocates more to sexual reproduction than the two other species.