Leaf morphology plasticity in response to light environment in deciduous tree species and its implication on forest succession

Sun leaves of five deciduous tree species were shaded, while shade leaves of the same species were exposed to direct rays of the sun prior to budbreak and during leaf expansion. Thickness, area, and density thickness (fresh weight per unit area) were measured and compared with sun and shade leaves that were used as a control. These parameters showed a considerable differentiation in leaf structure both for the control and treated leaves, particularly with very tolerant (American beech and sugar maple) and intermediate (yellow birch) species; this was apparently associated with the prevailing light conditions around a particular leaf from budbreak and during its development. Intermediate (red maple) and very intolerant (trembling aspen) species did not show true sun and shade leaves. The impact of these leaf adaptations on forest succession is also discussed