Date of Award


Degree Type


Degree Name

Doctor of Philosophy


This study addresses the problem of relating compositional variation in boreal vegetation to underlying deterministic (environmental) and probabilistic (primarily historical) influences. The problem of determining plot size is addressed, and a statistical optimization procedure outlined. Alternative ordination strategies are compared (using simulated data), and the advantages of non-metric multidimensional scaling discussed.;The vegetation studied occurs along the southern fringe of the boreal forest near Elk Lake, Ontario. Lacustrine sand deposits are characteristic, but rocky hills overlain by finer soils and small rock outcrops also occur. Accumulation of peat typifies low-lying areas.;The study area, comprising 90 km('2), was intensively sampled using a restricted random strategy, vegetation and environmental data being obtained from 431 plots. Multivariate methods were used to summarize and interpret the data: cluster analysis to delineate vegetation types and species groupings, and ordination to summarize trends in vegetational composition, to examine interspecific associations of species, and to summarize relationships between delineated types and species groupings.;Initial analyses led to the recognition of two distinct groupings: wetlands (132 plots) and uplands (299 plots). Within the wetlands, nine distinct vegetation types were recognized. Ordination results indicated the importance of nutrient status, and factors related to nutrient availability, in determining vegetation composition. Analyses of the upland sites indicated the importance of moisture availability. In xeric, oligotrophic habitats, ten vegetation types dominated by jack pine were recognized, and a continuum related to moisture availability indicated. In mesic, mesotrophic upland habitats, seven types, related to substate type and moisture status, were delineated. The influence of fire history in determining vegetation composition is also discussed.



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