kroun shahy·nes | /ˈkrau̇n ˈʃaɪ.nəs/
Many a xylophile (lover of woodlands) will have gazed skywards and noticed a distinct jigsaw-like pattern in the canopy. Known as crown shyness, it’s more common but not restricted to warmer climes and amongst trees of the same species. It can however occur in mixed woodlands and even within the same tree, as with the black beeches pictured.
There’s no consensus on what causes crown shyness. Depending on conditions, the answer is likely to be either wind damage or an evolved strategy of avoidance – and sometimes a combination of both. Studies of eucalyptus in Australia and black mangroves in Costa Rica have suggested wind is the main cause – the delicate buds and young leaves of the outer branches being killed by abrasive contact with their neighbours. In the mangroves, the outer branches could also have become interlocked whilst growing in calm conditions but were severely damaged when the winds returned and tore them apart. That said, studies in the cloud forests of Costa Rica found there was no more crown shyness in areas exposed to high winds than in sheltered areas.
Another study of Malay camphors found no evidence of wind abrasion, suggesting instead that the trees may be using their photoreceptors to sense far-red light, backscattered from neighbouring leaves. When this reflected light is detected, growth is stopped or redirected in the same fashion that many trees sense blue light to avoid growing into shade.
Whatever the mechanism, there are benefits to this arboreal social distancing. Crown shyness calls a truce on the potentially damaging competition for resources, and the gaps help keep the spread of pests and diseases at bay.
Introduction Aeolian Alpenglow Apricity Asperous
Benthos Crepuscular Crispate Crown shyness
Desire lines Dreich Endragoned Edgelands
Frondescence Fumarole Gluggaveður Gossamer
Karst Komorebi Lawrence Long acre
Machair Monkey’s wedding Moonglade
Psithurism Quartz Rakuyou Roaring forties
Snag Soft estate Specular, diffuse and pellucid
Spoondrift Steam fog Swash zone Sylvan