The objectives of this study were to examine overstorey and understorey dynamics over a 22 year period in Pinus contorta dominated communities in Banff and Jasper National Parks, and to attempt to relate differences in community dynamics at different stands to site specific factors such as moisture regime.

Four 1 ha plots were established by R. Hnatiuk in 1967 and represented three moisture regime classes. These sites were re-established and re-inventoried in 1989 by the author.

Despite extensive tree mortality in the Xeric and Mesic plots, the stands remained dominated by Pinus contorta as conditions were unfavourable for spruce and fir recruitment. However fir and/or spruce recruitment was abundant in the two Moist plots and these species became increasingly larger components of the tree canopy indicating that these stands are seral to communities dominated by mixtures of Pinus, Picea, and Abies.

Understorey dynamics was characterized by large increases in vascular species cover in the three lower elevation sites and by large bryoid cover increases at all four sites.

The overstorey and understorey dynamics were influenced by a complex range of factors including moisture regime, elevation, site history, tree density, and ungulate populations. (Abstract shortened by UMI.)