Functional ecology of advance regeneration in relation to light in boreal forests

This paper reviews aspects of the functional ecology of naturally establish ed tree seedlings in the boreal forests of North America with an emphasis o n the relationship between light availability and the growth and survival o f shade tolerant conifers up to pole size. Shade tolerant conifer species s uch as firs and spruces tend to have a lower specific leaf mass, photosynth etic rate at saturation, live crown ratio, STAR (shoot silhouette area to t otal needle surface area ratio), and root to shoot ratio than the shade int olerant pines. The inability of intolerant species such as the pines and as pen to survive in shade appears to be mainly the result of characteristics at the. shoot, crown, and whole-tree levels and not at the leaf level. Alth ough firs and spruces frequently coexist in shaded understories, they do no t have identical growth patterns and crown architectures. We propose a simp le framework based on the maximum height that different tree species can su stain in shade, which may help managers determine the timing of partial or complete harvests. Consideration of these functional aspects of regeneratio n is important to the understanding of boreal forest dynamics and can be us eful to forest managers seeking to develop or assess novel silvicultural sy stems.