Assessing a decaying Oak with a Tree Preservation Order
Client: Mr Rees, Swansea
Mr Rees contacted me in October 2018 initially asking for my assistance in carrying out a sonic tomography scan on an oak tree in his garden. The tree was subject to a Tree Preservation Order (TPO) and there was a long history of previous inspections and tree work applications to Swansea Borough Council. The existence of previous applications allowed me to see the history, documents and photographs on-line by accessing the Council’s website.
Assessing The Oak Tree
Mr Rees was concerned by the presence of an open decay cavity at approximately 4m above ground, together with other visible signs of degraded wood, and the presence of brackets of the decay fungus Laetiporus sulphureus (Chicken of the Woods). A series of cursory inspections by other tree ‘professionals’ had failed to adequately inspect the tree and address Mr Rees’ concerns. One professional had described the tree as a ‘veteran’ while another had suggested that tomography should be carried out. None had inspected the cavity from anything other than ground level.
As my conversation with Mr Rees developed, it became apparent that the large number of previous inspections undertaken, combined with conflicting advice Mr Rees had received had created a situation in which it wasn’t clear to the client how to proceed. Mr Rees was reluctant to commit to sonic tomography if it wasn’t the most appropriate course of action.
At this stage I hadn’t seen the tree and to help Mr Rees move forwards I undertook to carry out a visual inspection from rope and harness first and only carry out tomography during the same visit only if it was strictly necessary.
I attended site at the end of October, performed a ground-based assessment, followed by a climbing inspection according to the provisions of Aerial Inspections: A Guide to Good Practise (Arboricultural Association, 2017). By carefully mapping the various decay features using tree morphology, sounding mallet, metal probe and tape measure I was able to demonstrate that a widespread complex of coalesced decay existed in the main load-bearing bifurcation and stem immediately below it. Sonic tomography was not necessary.
Veteran tree assessment using the RAVEN scoring system demonstrated that the tree was NOT a veteran tree.Risk assessment using the THREATS tree hazard scoring system indicated that the tree should be felled within 4 weeks.
Identifying The Decay
In order to represent the inter-relatedness of the decay features, I produced a sketch representation with diagramatic explanation of certain key points. My report was supplied to Mr Rees within five working days of site attendance and was in turn passed to the Council tree officer the next day. Permission to fell was immediately granted.
The tree was felled one month later and Mr Rees supplied me with a photographic record of the wood as it was cut up.
The photograph reveals four things:
- The causative organism produced a cubical brown rot consistent with the presence of L. sulphureus.
- The decay from the main cavity penetrated the entire cross section of the tree to effectively create a ‘crack-like’ feature and the mechanism for the main cavity to communicate with smaller ones on opposite sides of the same region of decay.
- More importantly, this feature transected the tree roughly across the main union and provided the potential for the two primary boughs to move independently of each other. Thus, a mechanism existed for the tree to tear itself apart at the union under strong or squally wind conditions.
- Decayed branch stubs penetrated right to the centre of the heartwood. The pointed cones of decay so created provided a means for crack propagation across the remaining part of the cross section. Decay coalescence had definitely occurred.
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What our Clients say
It's extremely important to us that our Clients are 100% satisfied with all work that we carry out, here is just some of the feedback that we have collated from our client portfolio...
“Your report is excellent and appears very clear to me. Thank you so much for doing such a professional job and for doing such an impressive report and so quickly… Your diagnosis was spot on. There was extensive decay in the region you had identified. In the words of the guys who felled it "...it was definitely the right call"! Thanks again for doing such a professional job. Two of my neighbours want to commission you to assess their trees and I’ll be passing on your details.”