Massive limb failure of a mature oak pollard

Around a month ago, after a very long period of sustained hot and impossibly dry weather, I became alerted to the quite incredible failure of a single bole from a lapsed oak pollard. As can be seen in the images below, the failure I saw once I arrived at the site left me slightly speechless, though given the absurdly dry and hot weather over the weeks prior it was one that was not entirely unexpected.

According to residents who lived nearby, the failure occurred at around 19:00 in the evening, after a very warm and still morning and afternoon. The sound, it is alleged, was akin to (I quote) “a mass of scaffold collapsing”. Given the sheer size and weight of the bole, which is in itself larger than many trees, that isn’t all too farfetched of a description. Having heard lorries tear off moderately-sized ash limbs, which generates a sound almost like a gunshot, it’s not a sound one forgets quickly.

Certainly, the timing of the failure piques interest. It can be proposed that this failure was potentially in alignment with the phenomenon known as ‘summer branch drop’, as there had not been any other means of mechanical loading on this tree whatsoever in quite some weeks (ignoring the odd slight breeze). The failed area also showed no sign of rot. On the opposite side of the tree, on an old pruning wound, I saw a Laetiporus sulphureus fruiting body the year before, though the brown rot did not appear to have impacted upon this area whatsoever. Quite simply, it was as if the limb just slipped out of its socket.

summer-limb-drop-1
Not the view you want to see every time you go and look at some lovely parkland trees…
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From the side, we can appreciate just how major this faulure was.
summer-limb-drop-3
A ‘clean’ tear, with the limb having completed severed all vascular contact with the trunk.
summer-limb-drop-4
Standing underneath the bole, we can also observe a huge buttress root that may – to a degree – suggest just how much inherent mechanical loading the low trunk was being placed under.
summer-limb-drop-5
Walking further around the southern side of the tree, perhaps the pronounced buttress root is worthy of even more recognition.
summer-limb-drop-6
A closer view of the ‘socket’.
summer-limb-drop-7
And from the other side of the tree, looking south into the park.
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Massive limb failure of a mature oak pollard

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