ECOTONAL PLANT COMMUNITIES NORTH OF THE FOREST BORDER, DEEWATIN, N. W. T., CENTRAL CANADA.
WISCONSIN UNIV MADISON DEPT OF METEOROLOGY
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The vegetation of the tundra ecotone region which extends from the forest border at the south end of Ennadai Lake northward to Dubawnt Lake, some 150 miles distant, is characterized by floristically depauperate communities in the region immediately adjacent to the forest border and by an increasing number of typically Arctic species northward. This increase in richness of Arctic components in the vegetation appears related to the increasing prevalence northward of habitat conditions associated with Arctic air masses, since other factors such as topography, surficial geology, and soil parent material seem relatively uniform throughout the region, and since sufficient time has elapsed following the most recent major climatic change to permit species to migrate to the geographical limits of their environmental tolerance. Recent work has shown that the mean position of the Arctic frontal zone is coincident with the forest border. It appears that decreasing frequency northward of atmospheric conditions related to the frontal zone is associated with increasing values representing presence of Arctic species in the plant communities along a line northward. Thus, from the evidence presented, it appears possible to define the extent of this climatic transition zone on the basis of the structure of the plant communities comprising the vegetation of the area, although ultimate confirmation of the hypothesis may have to await more detailed climatic observations. Author