VEGETATION ENVIRONMENT RELATIONSHIPS OF AN INLAND BOREAL SALT PAN

Vegetation composition and community structure of boreal inland salt pans near the shore of Dawson Bay, Lake Winnipegosis, Manitoba, were examined. Eight vegetation associations and eight species groups were described from the site. Most of the vegetation associations were dominated by a single graminoid or graminoid-like species. Species composition in the most saline areas was similar to that of prairie salt pans to the south, whereas the vegetation of less saline areas showed affinities to both prairie and boreal forest. Examination of vegetation-environment relationships indicated that soil salinity was the moost important factor determining vegetation pattern. Other soil factors such as nutient levels, bulk density, and percent organic matter were of secondary importance. Species richness increased with decreasing salinity, but trends in Shannon-Weaver diversity and evenness along the salinity gradient were more complex. Despite the salinity gradient being environmentally continuous, strong vegetational discontinuities were noted. It is suggested that these discontinuities arose through interspecific competitive interaction and displacement mediated by differences in the salt tolerance of species.