Using Sonic Tomography to Assess the Extent of Wood Decay – by Joel Gray

From time to time we are asked to assess the structural integrity of a specimen which maybe raising concerns for a customer. An indicator of potential decay is sometimes (but not limited to) a fungal fruiting body protruding from the wood or root area around a tree, and depending on what species of fungi these fruiting bodies belong to, we can gauge whether a look inside the stem is necessary or not.

A very efficient way of doing this is by using a Tomograph to send sound waves through the wood with the use of strategically placed sonic sensors around the circumference of the trees stem. These sensors record the speed of the sound waves moving through solid or decayed wood masses and produce a colour coded image revealing any decay patterns within the stem itself.

We were recently invited to inspect a mature and prominent Copper Beech tree in Exeter, which was infected with Meripilus giganteus (a root and stem base decaying fungi) and assess the possible extent of decay within the tree’s lower stem.

Unfortunately in this case a Tomograph inspection revealed that the wood was significantly compromised on one side of the tree which could have increased the risk of the tree collapsing into a nearby school playground. The Tomograph image is reproduced below and shows pockets of decay (coloured pink or blue) extending around the southern circumference of the tree.

With the help of this technology we were able to make a more informed decision on the appropriate remedial action to take. With the owners desire to retain the Beech tree for as long as possible, we recommended a significant weight and height reduction so as to considerably reduce the risk of the tree falling. Further Tomograph inspections can be undertaken in the future, we can then evaluate the rate of spread of decay within the tree and recommend appropriate action as needed.

In other cases we have used Tomography to ease a client’s concern over the stability of a tree by clearly showing a sound and solid wood structure beneath the bark, leading to peace of mind and the retention of a specimen that might otherwise have been needlessly felled.

Inspections start from around £150 + VAT and we would be happy to advise on the suitability of this technology for any particular tree concern that you may have. Contact Graham Joyce if you would like to discuss further.

By Anthony Arrow | May 3rd, 2017