In the below image, we can clearly see how the oak has laid down significantly greater growth increments beneath the large lateral limb, compared to the growth increments above. Known as the axiom of uniform stress, I feel this is a wonderful example of how trees will seek to optimise their structure in order to minimise acute stress build-up. If the trunk’s girth was not so much broader underneath the limb, the limb may have already failed. Just think of the weight of that limb…!
Arboriculture 