STRUCTURAL-COMPOSITIONAL VARIATION IN 3 AGE-CLASSES OF TEMPERATE RAIN-FORESTS IN SOUTHERN COASTAL BRITISH-COLUMBIA

Relationships between forest structure and species composition were ex amined in three age-classes of temperate rain forest in southern coast al British Columbia. Old forests (> 250 years) exhibited greater struc tural and compositional heterogeneity than young (31-60 years) and mat ure (61-80 years) 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 (R(c ) = 0.84), but a substantial amount of total variation remained unexpl ained by the analysis. Principal component analysis (PCA) axis 1 of sp ecies composition separated the lower elevation (warmer and drier) mat ure forests from the higher elevation (cooler and wetter) young and ol d forests. PCA axis I of structure separated the young and mature fore sts as a group from the old forests. PCAs of the separate age-classes indicated weaker compositional -structural linkages than with all age- classes combined. Study area differences explained greater proportions of variation in young and mature forests (up to 53%) than in old fore sts (< 10%). The results indicate a slow recovery process following im pacts from human disturbance in coastal forests.