# What can passive electrical signals tell us about tree transpiration? One year of self-potential observation at three test sites in a Mediterranean Climate

Kaiyan Hu, Bertille Loiseau, Simon D Carrière, Nolwenn Lesparre, Cédric Champollion, Nicolas K Martin-Stpaul, Niklas Linde, Damien Jougnot

► To cite this version:

Kaiyan Hu, Bertille Loiseau, Simon D Carrière, Nolwenn Lesparre, Cédric Champollion, et al.. What can passive electrical signals tell us about tree transpiration? One year of self-potential observation at three test sites in a Mediterranean Climate. eLTER Science Conference 2025, Jun 2025, Tampere, Finland. 10.3897/aca.8.e151930. hal-05403624

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# What can passive electrical signals tell us about tree transpiration? One year of self-potential observation at three test sites in a Mediterranean Climate

Kaiyan Hu†, Bertille Loiseau§, Simon D. Carrière¶, Nolwenn Lesparre¶, Cédric Champollion#, Nicolas K. Martin-StPaul#, Niklas Linde«, Damien Jougnot§

‡ School of Geophysics and Geomatics, China University of Geosciences, Wuhan, China

§ Sorbonne Université, CNRS, UMR 7619 METIS, Paris, France

¶ UMR 5569 HSM, Univ. Montpellier, CNRS, IMT, IRD, Montpellier, France

Université de Strasbourg, CNRS, EOST, ENGEES, ITES UMR 7063, Strasbourg, France

\# Géosciences Montpellier, Université de Montpellier, Montpellier, France

□ INRAE, URFM, Domaine Saint Paul, Avignon, France

« Institute of Earth Sciences, University of Lausanne, Lausanne, Switzerland

Corresponding author: Damien Jougnot (damien.jougnot@upmc.fr)

Received: 03 Mar 2025 | Published: 28 May 2025

Citation: Hu K, Loiseau B, Carrière SD, Lesparre N, Champollion C, Martin-StPaul NK, Linde N, Jougnot D (2025) What can passive electrical signals tell us about tree transpiration? One year of self-potential observation at three test sites in a Mediterranean Climate. ARPHA Conference Abstracts 8: e151930.

https://doi.org/10.3897/aca.8.e151930

## Abstract

Tree transpiration is a critical process of the water cycle and its observation and quantification are essential to better understand terrestrial ecosystem dynamics. While sap flow measurements provide direct estimates of individual tree transpiration, their reliance on empirical calibration and a rather high energy consumption (due to heat generation) can be strong limiting factors. The self-potential (SP) method, a passive geophysical approach, presents a promising alternative for assessing transpiration rates, although the electrophysiological processes driving SP signals in trees remain underexplored (Fig. 1).
<figure><img src="image_3.png" /><figcaption>Figure 1. doi</figcaption></figure>

Schematic diagram of the tree SP approach and the scales involved (from Hu et al. (2024)):
(a) single tree, (b) horizontal and vertical cross sections of the trunk, (c) vertical cross sections of xylem and phloem vessels, (d) cellulose structure, (e) sketch of the electrical double layer at the cell-sap interface where the electrokinetic coupling takes place. Parts of the figures have been obtained through BioRender.com (2024).

This study presents a year-long monitoring of SP and sap velocity in three tree species at three Critical Zone Observatories different in a Mediterranean climate (from OZCAR and ICOS research infrastructures). Using wavelet coherence analysis and variational mode decomposition, our findings reveal strong coherence between SP and sap velocity at diurnal time scales, with coherence diminishing and phase shifts increasing under higher water supply conditions. Electrokinetic coupling coefficients, derived from linear regression between SP and sap velocity variations, align with values typical of porous geological media. During dry seasons, the electrokinetic effect dominates SP signals, suggesting its potential as a tool for evaluating transpiration rates. This research demonstrates the feasibility of integrating geophysical techniques into long-term observations of ecohydrological systems to better understand plant-water interactions in the Critical Zone.

Keywords

Tree transpiration, Sap flow, Self-potential, Critical Zone Observatories
**Presenting author**

Damien Jougnot

**Presented at**

POSTER

**Conflicts of interest**

The authors have declared that no competing interests exist.

**References**

* Hu K, Loiseau B, Carrière S, Lesparre N, Champollion C, Martin-StPaul N, Linde N, Jougnot D (2024) Self-potential signals related to tree transpiration in a Mediterranean climate. Hydrology and Earth System Sciences Discussions 1-30. https://doi.org/10.5194/hess-2024-240