Electrical resistivity tomography numerical modeling for decay characteristic analysis in ancient tree stems

Abstract Ancient trees, as scarce ecological resources and cultural heritage, have long been a focus of forestry research, with the degree of internal decay in their stems directly affecting their ecological and landscape value. This study leverages the high sensitivity of electrical resistivity to decay and innovatively introduces a nondestructive testing technique from geophysics—electrical resistivity tomography (ERT). This nondestructive testing method replaces conventional invasive drilling techniques, thereby avoiding secondary damage. In response to the geometric characteristics of stems, this paper designs a circular observation system and, based on the finite element principle, simulates and evaluates the imaging sensitivity of different electrode configurations (dipole–dipole, Wenner, and Schlumberger) and angular spacings (15°, 22.5°, and 45°) to decay characteristics. The results indicate that the dipole–dipole configuration combined with 22.5° angular spacing can accurately identify the edge contours and positions of low-resistivity zones in early-stage decay; it can effectively localize the central positions of late-stage cavities, but obvious annular artifacts persist in the peripheral areas of cross-sections, reducing resolution. The observation system established in this study can optimize detection standards, improve the imaging results of ERT, significantly reduce operation and maintenance costs, and more efficiently provide technical support for the dynamic detection and monitoring of the health status of ancient trees.