What is crown shy­ness?

BBC Wildlife Magazine - - Our Wild World - Phil Gates

ATem­per­at­ede­cid­u­ous forests tend to com­prise a mix­ture of species of vary­ing ages, with ma­ture trees form­ing a canopy with lay­ers of over­lap­ping branches that all re­ceive a share of light as the sun moves across the sky. But in some other forests, par­tic­u­larly those with lodge­pole pines, eu­ca­lyp­tus, man­groves and cer­tain trop­i­cal dipte­ro­carp trees, ‘crown shy­ness’ pre­vents neigh­bour­ing branches from over­lap­ping and shad­ing one an­other. From be­low, the tree­tops ap­pear to lock to­gether like the pieces of a jig­saw puz­zle, sep­a­rated by channels of blue sky.

Botanists are still de­bat­ing the mech­a­nism be­hind the mu­tual shade-avoid­ance. Some think that the phys­i­cal abra­sion be­tween branches col­lid­ing on a windy day in­hibits growth, thus main­tain­ing per­sonal space be­tween trees. Oth­ers claim that buds at the end of twigs sense the far-red (one down from in­fra-red) light re­flected from neigh­bour­ing fo­liage, which pre­vents growth to­wards each other.

Crown shy­ness demon­strated by Ka­pur trees in Malaysia, rem­i­nis­cent of the pat­terns cre­ated in dry, cracked earth.

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