PiCUS TreeTronic

The PiCUS TreeTronic is an electric resistance tomograph and when used in conjunction with sonic tomography it can provide a more complete assessment of internal decay (such as wall thickness and stage of decay) than when using either product independently. Electric tomography is particularly useful at identifying early stages of decay when compared to a healthy specimen of the same species. The electrical resistivity of wood fluctuates due to moisture content, atmospheric temperatureand the accumulation of cations (SIMPSON & TENWOLDE, 1999). Generally speaking, the electrical resistivity of wood decreases as it becomes decayed. Furthermore, the moisture content of living sapwood is greater than heartwood, but this varies between trees of both the same and different species. Research has shown that moisture content in comparison to dry wood weight varies between 30% and 200% in different tree species and can fluctuate in an individual tree due to humidity, precipitation and temperature. These atmospheric conditions also affect rate of fungal infection (TIITTA, 2006). Moisture content of wood infected with brown rot varies between 60% and 80%. But greater still, the moisture content of wood infected with white rot, soft rot, or bacteria can exceed 300%.

To summarise, the electrical resistance of wood is affected by moisture content, temperature (plus other season variations) and level of decay. Despite these variances, it is still possible to detect decay in a tree by comparing it to a healthy specimen of the same species (which creates additional work during assessment). It has however been identified that electric resistance tomography does not identify decay well in trees with hollows (hollows increase electric resistivity) and for that reason it is best utilized when paired with sonic tomography.