Complex Resistivity (CR) of Wood and Standing Trees

Complex resistivity (CR) has been used to investigate the properties and the extent of damage in wood and standing trees. Our laboratory experiments have proved that wood’s anisotropy influences its electrical behaviour. It is a well-established fact that wood exhibits the lowest resistivity amplitudes in the axial direction compared to that in tangential and radial directions. It has been shown that anisotropy affects not only the amplitude but also the phase. Phase values are the highest in the axial direction, particularly in the lower frequency range. The changes in resistivity due to fungi-induced damage were investigated in a long-term laboratory test. With progressing damage, both resistivity and phase decrease. The phase also shows sensitivity to the changes in the structure of wood cell. CR Tomography (CRT) has been employed in the field to detect fungi-infected zones in fallen trees. A number of factors such as the type and age of the tree, and the season seem to influence the CRT results. Among those, the effect of seasonal changes has been demonstrated here. Furthermore CRT can be used to characterise fungi-infected zones in the tree.