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UBC Theses and Dissertations

Phytogeocoenoses of a coastal lowland ecosystem, Devon island, N.W.T. Barrett, Paul Edward


During the summer periods of 1967-1969 field studies were undertaken at a Coastal Lowland ecosystem, on the north coast of Devon Island, N.W.T. Canada (75° 41’ N; 84° 33’ W). The study area is a naturally delineated strand flat roughly sixteen square miles in size. It is segregated from the Interior regions of the Island by a vertical escarpment, which rises sharply from the eastern border of the lowland to an elevation of approximately 1000 feet. The remaining borders are surrounded by the waters of Jones Sound. Such lowland ecosystems appear markedly distinct from the more extensive Inland plateau regions. Botanically they are relatively very rich. Intensive fluvio-glaclal activity combined with a diversity of parent rock provides a number of distinctive environments for plant colonization. Ninety-three species of vascular plants have been collected within this limited area, and closed stands of vegetation are common. This Is In sharp contrast to most of the Canadian high arctic where polar desert conditions prevail over the greater portion of the landscape and vegetation is normally sparse. Seventy-three stands were selected from the vegetational mosaic for analysis using standard European phytosociological techniques. Soil excavations were made at each location and samples from all genetic horizons returned to the laboratory for physical and chemical analysis. Stands from various vegetation types were also monitored for selected, environmental measurements throughout the growing season. Measurements included soil temperature, soil moisture and active layer development. Synthesis of floristic and environmental data from these stands resulted in the construction of a hierarchical scheme of phytogeocoenotic classification for the lowland system. Units were named in accordance with standard Braun-Blanquet terminology. Seven synsystematic orders, seven alliances and nine plant associations are discussed of which three orders, six alliances and all nine plant associations are newly described. The order Carlcetalia fuscae dominates the study area and imparts to the lowland system as a whole the character of a wet graminoid meadow. The Phyllodoco - Cassiopetalia is also an extensively developed synsystematic order within the lowland region. Maximum plant association diversity develops within the order Dryadetalla. While occupying a smaller proportion of the landscape it is in this order that the zonal associations of the lowland are found. The Alectorietalia, Petasitetalia frigid!, Sall-cetalia arcticae and Arabidetalia orders, while less extensively developed, are nevertheless distinctive units. All major arctic soil groups recognized In Tedrow's classifications scheme are present in the area. Strong correlation exists between vegetation and underlying soil type. The most common soils are the gleysolic Meadow Tundra soils which underlie the Caricetum stantis. An objective classification of the 73 stands was generated from the floristic data. Sorenson’s index was used to calculate a complete matrix of interstand similarity values. These were then subjected to clustering techniques and illustrated in the form of a two-dimensional dendrogram. Clusters generated in this fashion are identical, at the association level, to those constructed by the synthesis techniques of the Braun-Blanquet method. At higher levels of integration (order and alliance) no associations were clustered outside the subjectively derived hierarchy. Individual dendrograms were generated in the same fashion utilizing only selected components of the floristic matrix. Strong similarities exist between the phytogeocoenoses of the Devon Island lowlands and those of other tundra locations, particularly the Dryadion (octopetalae) described from Svalbard. This supports the view that plant communities as well as individual species may be circumpolar in nature. Sharply defined ecotones, homogeneous environmental conditions and the presence of the characteristic species combinations occur in the nine phytogeocoenoses described. This supports the thesis that natural assemblages of vegetation may be selected and described from the tundra mosaic without recourse to "special" synecologlcal techniques as has been suggested.

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