The Turkey Oak

Initial tree inspection

I was recommended to James and Susie Suter to inspect a Turkey Oak with a significant fungal bracket that was adjacent to the car park at the Gliffaes Country Hotel. I carried out my inspection and identified that the tree had two different species of fungal infection and recommended that to remove the risk the tree could be removed or we could do further tests to determine the extent of the decay in the tree and make a more informed decision on whether to retain the tree or remove it. Because of the significance of the tree, my clients chose to carry out a more detailed inspection and engaged a colleague to carry out an internal decay assessment using a Tomograph.

A Tomograph is a piece of equipment that uses 12 sensors set around the circumference of the tree’s stem. Each sensor is tapped with a hammer and the resulting sound waves are recorded. The ability of the sound waves to travel through the woody tissue is affected by the integrity of the wood  and a reading id created by mapping the speed at which the sound waves travel between each of the sensors. This is then depicted as a colour diagram where the green and brown represents sound wood and the blue and purple represent areas of decay or disfunction.

For the Turkey Oak at Gliffaes the tomograph results identify the location of the three fungal fruiting bodies. Between sensor points 2 & 3 and 6 & 7 there are Ganoderma applinatum fruiting bodies and between points 11 & 12 there is a Ganoderma adspersum fruiting body. The significance of this is that the Ganoderma species are white rot fungi, meaning that they decay the lignin in the trees woody tissue, removing a significant part of the trees structural strength and leaving a soft damp tissue in the areas of decay. The Ganoderma adspersum also has the ability to break through cell walls and internal boundaries that the tree sets up, known as pseudosclerotic plates, meaning it is potentially more aggressive.

The reading appeared to show extensive decay, however when inspecting the tree it was noticeable that the tree was also putting on significant reaction growth in its buttresses. After a long period of discussion, it was decided that the while the tree had significant decay fungi present, the tomograph reading could have been influenced by internal shakes that are a feature of Turkey oak. This was because the tomograph did not reflect the extent of the reaction growth that was visible on the tree. On consultation with our client, it was decided to retain the tree with a crown reduction. This would reduced the leverage on the tree’s stem and would also reduce the likelihood of limbs being shed, both of which enable retention but reduce the risk of failure and impact on the target area, which was the car park.

It was also understood that the reduction work to the tree would also be likely to allow the fungal infections to increase in vitality as the tree would allocate its resources to preventing decay around the pruning wounds, which in turn meant it would have fewer resources to combat the existing infection, meaning that the fungi would be more likely to increase the extent of the decay column at the base of the tree.

The tree was retained for a further five years, with an annual inspect to assess the vitality of the tree and the vigour of the fungal fruiting bodies. After five years, a discussion was had with the client about further works to the tree and whether or not to carry out an additional internal decay assessment to see how the decay had changed since the previous assessment.

In the intervening years, our involvement with Gliffaes had progressed from simply assessing tree condition to creating a tree walk and developing a planting programme to create and arboretum.

This completely changed the way the site and the trees were assessed, and because we could see that the retention of the tree was now a short-term management option and the early planting was becoming established, we could see the opportunity of succession planting becoming available. It was therefore decided to remove the crown of the tree and leave the stem as a standing dead wood habitat and invest the resources that would have been used to retain the tree into planting new trees to succeed it.

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