Spatial pattern of vegetation in high arctic sedge meadows

The spatial pattern of the vegetation in sedge meadows was studied at two s ites, one grazed and one ungrazed, in the High Arctic on Ellesmere Island. The patterns of single species, of pairs of species, and of the vegetation as a whole were investigated using data from belt transects and several met hods of analysis. The scales of covariance of the species with the microtop ography were also analysed. Only at the site with the most pronounced devel opment of a hummock-hollow system did this covariance match well with known ecological characteristics of the species. The covariances between species did not clearly reflect these ecological characteristics, indicating that the vegetation is no: neatly divided into a mosaic of a dry hummock phase a nd a wet hollow phase. Similarly, the multi-species pattern did not closely match the scales of pattern of the individual species, another indication of the disorderliness of the spatial structure of these communities. A comp arison of the grazed and ungrazed sites shows that grazing further reduces the intensity and clarity of the pattern. There is, however, no evidence th at grazing changes the scales of pattern in these meadows.