Thirteen undisturbedPinus banksianaLamb. forests on Eutric Brunisols, derived from dune sands in the lower Peace River Valley, were analyzed quantitatively. Fort Vermilion has a dry, continental, subarctic macroclimate. Stands varied in age from 15 to 97 years, with tree volume increasing from 19 in younger to 193ensp;m3ensp;haminus;1in older stands. Cover of trees averaged 49, shrubs 7, dwarf shrubs 27, forbs 6, graminoids 1, feather mosses 4, caribou lichens 2. Based on recurrently dominant species of well-developed vascular strata and growth-form guilds, aPINUS BANKSIANA/ROSA ACICULARIS/ARCTOSTAPHYLOS UVA-URSIndash;LATHYRUS OCHROLEUCUScommunity type is postulated for xeric sandhill habitats. This type is probably seral to aPicea glauca(Moench) Voss climax, but frequent fires prevent this. Plant succession during the sampled 80-year age interval is characterized by (i) increasing dwarf shrub, forb, and graminoid cover, (ii) stabilization of vascular species richness at ca. 35 species per stand, (iii) decline and stabilization of Simpson's dominance index, (iv) increasing Shannonndash;Weaver diversity, and (v) progressively gentler dominancendash;diversity slope angles. The niche preemption model (geometric series) of species structure fits younger and older better than middle-aged stands, based on goodness of fit of regression lines (r2) to dominancendash;diversity curves.
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