If you found yourself underneath the crowns of an Eucalyptus forest, a Sitka spruce or a Larix Kaempferi, you would notice immediately the irregular gaps that show up beyond the higher leaves. The upper branches of these species, as well as the ones of many other (check out this Wikipedia link) avoid any type of contact, creating some distinctive escape routes amongst the branches of their crowns.
Below: picture by Dag Peak shared via Flickr – licence Creative Commons 2.0
The phenomenon started being debated in botany essays in the 20’s but still since then no certain explanation to the phenomenon has been found. Despite the type of tree (around 7 in total), the crown shyness event draws lines on the sky.
Even though there is no certainty about what pushes these species to behave in such a an unusual way, 3 main hypothesis have been suggested:
The first one explains the distance between the crowns with the need to reduce the mechanical damage caused by the wind which could lead the branches to hit and damage each others mutually.
The second one talks about the optimisation of the space to receive the sunlight in the best way possible, essential for the photosynthesis which otherwise would be hindered by the shadow that the leaves of the other tree would create.
The last hypothesised theory, even in terms of time, is the one believing that the event occurs in order to avoid the circulation of invasive parasites by keeping the tree beside at a distance and therefore by limiting the speed of proliferation of the harmful organisms.
Whatever the cause of such a phenomenon is, the the scenarios that the crown shyness create are extremely fascinating to look at.
Below: picture by Patrice78500 shared via Wikimedia Commons – public domain
Below: picture by Mikenorton shared via Wikimedia Commons – public domain