ENVIRONMENTAL-INFLUENCES ON THE STRUCTURE OF SEDGE MEADOWS IN THE CANADIAN HIGH ARCTIC

Wet sedge-dominated communities (sedge meadows) were sampled in five l owland eases in the Queen Elizabeth Islands of the Canadian High Arcti c to assess species-environment relationships. The sites spanned 4 deg rees of latitude, and varied in lithology and intensity of grazing by muskoxen (Ovibos moschatus). A suite of 8 vascular species were common in all meadow stands, with an additional 4-6 species found in most st ands. The position of these species in dominance-diversity curves was not significantly different between,orated and ungrazed meadows howeve r, the grazed sites appeared to follow a log-normal distribution, whil e the ungrazed sites were more geometric. Redundancy analysis indicate d that grazing intensity is important in determining structure in arct ic sedge meadows, largely through increasing the cover of bryophytes a nd the availability of nitrogen. Greatest species richness was found i n the more southerly sites which were moderately grazed and had divers ity in microtopography.