Gap dynamics theory proposes that forest canopy gaps provide the high light levels needed for regeneration. Little attention has been given to more gradual alternatives; however, recent studies have demonstrated declines in within-crown leaf area index with tree size in temperate forest trees. Our project builds on this previous research by assessing the prevalence of this age-related crown thinning phenomenon. We quantified crown openness for 18 dominant tree species in temperate and tropical forests (n = 1786 trees). Separate pooled groupings of tropical and temperate species showed significantly positive relationships between openness and DBH (p<0.001). Of the 9 sampled species showing positive relationships, significance (p< 0.05) was detected in 3 out of 10 tropical species and 1 out of 8 temperate species. Two temperate species showed significantly reduced canopy openness with size. These trends highlight the role that very large trees play in influencing light availability for understorey regeneration.

Gap dynamics theory proposes that forest canopy gaps provide the high light levels needed for regeneration. Little attention has been given to more gradual alternatives; however, recent studies have demonstrated declines in within-crown leaf area index with tree size in temperate forest trees. Our project builds on this previous research by assessing the prevalence of this age-related crown thinning phenomenon. We quantified crown openness for 18 dominant tree species in temperate and tropical forests (n = 1786 trees). Separate pooled groupings of tropical and temperate species showed significantly positive relationships between openness and DBH (p<0.001). Of the 9 sampled species showing positive relationships, significance (p< 0.05) was detected in 3 out of 10 tropical species and 1 out of 8 temperate species. Two temperate species showed significantly reduced canopy openness with size. These trends highlight the role that very large trees play in influencing light availability for understorey regeneration.