Crown shyness

Photo credit: Dominyka Jurkštaitė, Boredpanda.com

James McDonald explains what crown shyness is.

In certain forests, when you look up you will see a network of cracks formed by gaps between the outermost edges of the tree branches. It looks like a precisely engineered jigsaw puzzle, each branch growing just perfectly so it almost—but not quite—touches the neighboring tree.

Some hypotheses as to why it happens, as summarized by McDonald.

• Abrasion, which happens when trees rub into one another during a windy day, causes trees to maintain shyness gaps in order to minimize this contact (Putz et al, 1984).
• But there's no difference between trees in windy areas than in not-so-windy ones (Rebertus, 1988), so there must be other factors that explain this behavior.