Age-related Crown Thinning: Common but not Universal in Tropical and Temperate Forest Trees

• Main Author: Quinn, Eadaoin Maria Ines
• Other Authors: Thomas, Sean C.
• Language: en_ca
• Published: 2013
• Subjects: gap dynamics; crown thinning; age-related; size-dependent; moosehorn; 0478; 0329
• Online Access: http://hdl.handle.net/1807/43309

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.