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Vegetation and environment in the Mackenzie River Delta, Northwest Territories : a study in subarctic ecology Gill, Donald Allen


The intent of this study is to describe and analyze the interrelations of vegetation and environment in the east-central sector of the Mackenzie River Delta, Northwest Territories. It traces the sequence and function of the allogenic events which create varying habitat systems and determines whether environmental modification, once initiated on terra nova is directional - in either a physical or floristic expression. In determining the sequence and influence of physical environmental factors, the following parameters were measured, employing standard instruments and field investigation techniques: micro-relief; depth, areal extent, and duration of flooding; thickness, areal extent, and particle-size distribution of annual deposits of alluvium; magnitude and significance of erosion; patterns of microclimatic variation (including air temperature and humidity, evaporativity, precipitation, wind speed, solar radiation, and net radiation); lake and channel temperatures; soil pH, moisture (hygrotope class), and temperature; development of varying active layer depths; and freezeback of the active layer. To analyze the vegetation of the study area, the phytosociologic methods of the Braun- Blanquet (Zurich-Montpellier) school were applied. Nine seral associations and the climax ecosystem were studied; each was fitted into a successional category. Plant succession was analyzed by reconstructing the course of vegetative development from pioneer to climax community with the aid of successional transects. Results of this study indicate that environmental and floristic changes in the Mackenzie Delta are directional - that given the formation of new ground, such as on the slipoff slope of a shifting channel, ecologic variation will follow a predictable direction. As the seral sequence advances, autogenic influences become dominant over the allogenic initiators until in the climax association, relatively steady-state conditions of environment and vegetation are attained.

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