The temporal evolution of the electrical signal generated by Pinus halepensis was measured in a sample of 15 trees. Weekly experiments were carried out during a long-term campaign lasting over a year, while trials with a high frequency of measurements were also performed during several days. In the latter case, day-night oscillations of the electrical magnitudes were observed. Additionally, punctual meteorological events such as rainfall and electrical storms affect the electrical signal as well. The measured electrical intensity grows exponentially with the voltage. In fact, no electrical intensity that exceeds the threshold of 0.01 μA is gathered when voltage values are lower than 0.6 V. In general, higher electrical signals were gathered during the rainy seasons with moderate temperatures; while very low signals, including few measures of zero intensity, were obtained during the most stressful periods over the year, mainly by mid-summer. There is a strong correlation between the rainfall and the electrical signal. The rain-intensity correlation, together with sustained intensity values during the reproductive period in spring, suggests that this electrical magnitude could be an indicator of the physiological state of the tree and thus used for in situ and minimally invasive forest monitoring.

Electric potential differences in living plants are explained by theories based on sap flow. In order to acquire more advanced knowledge about the spatial distribution of these electric potential measures in trees, this research aims to analyze electrical signals in a population of Aleppo pines (Pinus halepensis Mill.) in a representative Mediterranean forest ecosystem. The specific research objective is to assess some of the most significant factors that influence the distribution pattern of those electric signals: tree age, measurement type and electrode placement. The research has been conducted in representative forest stands, obtaining measurements of different representative trees. After a statistical evaluation of the obtained results, the main conclusions of our research are:

This study investigates the electrophysiological activity of Pinus halepensis to determine whether electrical responses differ among tree organs. Weekly bioelectric voltage measurements were conducted over one year in fifteen trees located in Gátova (Valencia, Spain), comparing electrical potentials between woody (trunk and twigs) and fine tissues (needles). Stainless-steel and platinum electrodes were used to record voltage signals, which were analyzed through linear regression and mixed-effects models. Results showed that voltages in the trunk were consistently higher than in the needles, yet both exhibited synchronized seasonal dynamics driven by shared physiological and environmental factors. The needle-to-trunk voltage ratio remained stable at approximately 60%, except during a summer drought, indicating coherent electrical coupling across organs. A strong linear relationship (R² = 0.98) confirmed that trunk signals serve as reliable surrogates for needle potentials. Organ-level analysis revealed a clear voltage hierarchy (trunk > twig > needle), largely attributable to anatomical and impedance differences. These findings identify the trunk as the optimal electrode placement site, enabling robust, non-destructive, and continuous measurements that can support future applications in wildfire risk assessment and forest monitoring.