I examined the effects of natural and anthropogenic disturbances on the patterns of species composition, tree regeneration, and forest architecture in old-growth forests from southern coastal British Columbia. This study was conducted in the submontane portion of the Coastal Western Hemlock Zone in the Vancouver watersheds, Pacific Spirit Park, and Clayoquot Sound. In the greater Vancouver area, old forests (250 yr) exhibited greater structural and compositional heterogeneity than young (31-60

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... r) and mature (61-80 yr) forests. Size class distributions of living and dead standing trees in the three age groups suggested both qualitative and quantitative differences in regeneration and mortality processes. The canonical correlation between structure and composition was high (Rc = 0.84) but a substantial amount of total variation remained unexplained by the analysis. PCA (principal component analysis) axis 1 of species composition separated the lower elevation (warmer/drier) mature forests from the higher elevation (cooler/wetter) young and old forests. PCA axis 1 of structure separated the young and mature forests from the old forests. Stand history reconstructions in the Capilano watershed and Clayoquot Sound indicated that frequent small-scale disturbances (0.1-0.2 treefalls/year) and relatively slow growth rates explain the relatively open character and complex architecture of old-growth cedar-hemlock forests. All three study plots exhibited reverse-J tree size distributions considered indicative of climax or steady-state conditions; however, age structures showed important differences. One plot originated from a fire 300 yr ago while the other two were over 1000 years old and showed no signs of catastrophic disturbances. Gap-phase dynamics may influence patterns of tree regeneration if small-scale disturbance events are relatively close in space and time. However, the spatial pattern of understory trees was not significantly correlated with canopy structure. Thus, the role of ga [...]