Electrical Phenomena in Trees and Wood: A Review

Purpose of review

This review covers electrical phenomena originating from the physical properties of wood, relevant to tree biology and timber industry applications. Membrane-associated cellular phenomena like action potentials are excluded. Trees exhibit diverse bioelectric processes of physical origin. The electrical properties of wood hold promise for advancing timber processing, and developing smart materials, while enhancing our understanding of tree-environment interactions.

Recent findings

Streaming and piezoelectric potentials have long histories but are now reinterpreted based on our better understanding of plants. Streaming potentials from sap flow, discounted in the 2000s, have been reinstated through recent publications addressing past inconsistencies with current data on xylem structure. Electro-osmotic flow is gaining new applications in timber drying. Wood, previously considered weakly piezoelectric, shows much stronger activity after fungal degradation, spurring interest in practical applications and the underlying mechanism – now better understood through new findings on the structure, deposition and deformation of wood cellulose. Internal variation in the electric (conductive and dielectric) properties of green logs facilitates innovative timber quality mapping methods. Emerging research on perturbation of the atmospheric and soil electric fields by trees offers insights into inter-organism interactions.

Summary

This review encompasses electrical measurement methods; electrokinetic phenomena, including streaming potentials and electro-osmotic timber drying; electric heating; mapping and technologies based on dielectric properties; wood-based electronics; electromechanical phenomena, including the piezoelectric effect and triboelectrification; atmospheric electricity around trees; and electrotaxis. Future research should explore electro-osmosis in wood and its applications. Electric potentials in green wood and living trees, generated through ion-transport mechanisms, need further exploration to elucidate charge separation processes.