Crown shyness (also canopy disengagement) is a phenomenon observed in some tree species, in which the crowns of fully stocked trees do not touch each other, forming a canopy with channel-like gaps. The phenomenon is most prevalent among trees of the same species, but also occurs between trees of different species. There exist many hypotheses as to why crown shyness is an adaptive behavior, and the most prominent theory, is that the gaps prevent the proliferation of invasive insects.
The phenomenon has been discussed in scientific literature since the 1920s. The variety of hypotheses and experimental results might suggest that there are multiple mechanisms across different species. Some hypotheses contend that trees in windy areas suffer physical damage as they collide with each other during winds. As the result of abrasions and collisions, there is an induced crown shyness response. However a Malaysian scholar who studied Dryobalanops aromatica, found no evidence of abrasions due to contact in that tree. He suggested that the growing tips were sensitive to light levels and stopped growing when nearing the adjacent foliage due to the induced shade.
Photo: Dag Peak