ArboTom Sonic Tomography (Picus) Decay Detection Testing

The ArboTom Tree Tomograph is an instrument for tree risk assessment and wood quality evaluation.  It will provide

Significantly more certainty about the extent of the decay in the tree and therefore the risk posed by the tree.  It uses sonic tomography to assess the internal structural condition of the tree trunk and interprets the results in a visual representation.  It is the most comprehensive form of tree decay detection testing that we have available to us at the present time.

Sonic tomography is often called Picus testing as this was the manufacturer of the first equipment to provide this service. This is similar to vacuum cleaners being known as Hoovers.

Technology has moved on quickly and there are now several manufacturers with equipment that provides this assessment albeit with slight differences in the method of assessment and the interpretation of results.

ArboTom quickly provides an impression of the inner condition of a tree. If used in conjunction with ArboRadix it can even detect roots below ground.

Sound waves travel through sound wood. Sensors around the tree measure the time it takes an impulse to travel through the wood and reach the other sensors. The collected data is simultaneously sent to a computer, which turns the data into a coloured image to visually represent the trees cross-section.

The sensitivity can be adjusted for different types of tree structure in terms of non-porous, diffuse porous ring porous or semi-ring/diffuse porous.  It can also be adjusted for different species of tree. This can be used to present a clearer and more accurate interpretation of the structural condition of the inside of any tree.  This is a fast and easy to set up test, that is non-invasive and non-destructive.

It is the only device on the market to measure at different heights of the tree simultaneously. The sensors are set at two or three separate horizontal levels and the acoustics across and between the levels is recorded. This allows it to produce a genuine three-dimensional interpretation of the internal condition of the tree.

The process is fairly simple. The area around the base of the tree is cleared at the height that is to be tested. This can include removing any epic comic growth or suffering as well as surrounding vegetation and man-made materials so that possible to get all the way around the tree.

North is established and is usually taken as the location for sensor one and a nail is driven through the bark into the wood of the tree. Then additional nails are inserted at the same height all the way around the tree with gaps of between 150mm and 400mm with nails put in wherever there is a significant change in the diameter of the tree. This will go on either side of the cavity as well as on the outside of any roots bulges or extending buttress roots. Each level can have up to 24 sensors with the standard pack and if two levels are being assessed same time that would be an average of 12 in each on each and if three levels then an average of eight.

Once all the nail locations have been located in three dimensions and input into the computer then sensors are placed on the nails and connected up to one another and the power supply.  At this point the striking point on each sensor is tapped 7 to 10 times to undertake the test.

This will result in a visual display on the computer showing the areas of sound would and decay with sound wood represented by green, degradation and loss of solidity represented by the orange colours and significant decay degradation or cavities represented by the red colours.

The computer will also show a safety factor for the tree and the direction and percentage of loss of mechanical strength with the direction displayed by directional arrow.

It will also show the path to each of the different sensors with these colour-coded in the same way as well as assessing the trunk strength based on its cross-section as compared to a perfect cylinder of the same diameter.

This data can be input into the ArboStApp package to assess the wind load of tree. Further assessments can be done of the spread of the roots with the addition of the Arbor Radix sensor and software.

It is also possible to investigate specific areas of a tree with a Resi PD micro drill, would drill or trunk corer, as a result of identifying targeting key areas using the sonic tomography information


These results images and charts can be used by experienced tree consultants to better inform their professional opinion. In no way should they be seen as definitive in their own right and are only there to provide additional information and guidance.

Traditional Treatment and Management

Traditionally at the first sign of decay fungal pathogen colonisation trees were felled, or at least heavily reduced. This was a safety first approach but as we learn more about fungal colonisation and the relationships between different tree species and different fungi species we are learning more about the often slow rate of decay and degradation.

The purpose of a heavy reduction was to significantly reduce the crown volume and more specifically the outer surface area. This greatly reduces the dynamic load on the tree in the form of movement as a result of wind speed.

Whilst this is all true the heavy reduction of a mature trees canopy will have a drastic impact on the physiological health of the tree. This is the leaf area of the tree that harvests the light energy and through the process of photosynthesis turns this into carbohydrates (sugars) which are available to the tree.

This energy supply has to be allocated to above and below ground growth, reproduction, and resisting disease and decay. A significant loss of this leaf area will have a catastrophic effect on the ability of the tree to deal with the decay itself. This often leads to a spiral of decline


Possible Recommendations for Treatment and Management

Whilst tree surgery remains a necessary management recommendation in some situations there are numerous other options to us as well now.  ArboTom sonic tomography (Picus) tree decay detection testing will enable us to make these recommendations more accurately and confidently.

These include the removal reduction containment of a target in the form of people or property within striking distance of the tree, as well as various nonsurgical solutions.

This includes regular management and retesting to assess the spread of decay and the rate of spread. We can also recommend climbing inspections. These will be supervised by a consultant with a report submitted that he will be taking guidance from a professional tree climber who will inspect defects at height, possibly using a camera and decay detection testing equipment to help him express the condition of the tree.

We can also undertake chlorophyll fluorescence testing or chlorophyll content testing to assess the physiological health of the tree.

We are also able to offer various soil treatment options. This benefits the tree greatly by improving its routing environment. This is vital for the tree to obtain water and nutrients groups roots and to exchange these for the carbohydrates obtained by the leaves.

A compacted soil will often have poor water percolation for gases exchange capacity and limited nutrient availability. Improving any or all of these will greatly improve the trees chances of resisting or overcoming disease and decay organisms.

There are various methods available for treating the soil. These include the application of mulch, the application of soil ameliorates, and the de compaction of the soil.


We now have an air spade or compressed air lance that we can use to significantly decompact may soils. This can result in significant improvements on tree health and can be combined with the application of nutrients to the soil or possibly to the trunk.

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