New research reveals bioelectrical coordination in trees during solar eclipse

In a forest deep within Italy’s Dolomite mountains, scientists have discovered that spruce trees may respond to solar eclipses not individually, but in unison. Using custom-built sensors, an international team from Italy, the UK, Spain, and Australia recorded synchronized electrical activity among the trees, suggesting they collectively sense and react to the sudden environmental changes triggered by the eclipse.

This phenomenon was observed during the solar eclipse on March 20, 2015, when the Moon briefly obscured the Sun. As light levels rapidly dropped, a cluster of Norway spruce trees in the Italian Alps exhibited coordinated electrical shifts—captured in real time by high-resolution sensors—pointing to a shared physiological response to the event.

The researchers suggest this kind of synchronization supports the idea of the forest functioning as a connected, living network. The work was led by Professor Alessandro Chiolerio and Professor Monica Gagliano.

Researchers carried out the study at two locations in Italy. One was Boves, where the eclipse coverage reached nearly 64%. Second was Turin, which experienced slightly different eclipse conditions and served as a control point. They chose nine Norway spruce trees and equipped each with non-invasive Ag/AgCl electrodes, placed in both the bark and nearby soil. This setup allowed them to track shifts in electrical potential between the trees and their environment.

The research team tracked electrical signals in real time, collecting data at millisecond intervals. Each tree was observed for hours before, during, and after the eclipse to build a full timeline of activity. Trees outside the eclipse zone were also monitored to compare with typical daily patterns.

Professor Chiolerio said the team used advanced tools like complexity measures and quantum field theory (QFT). Through this approach, they found a deeper kind of synchronization among trees that doesn’t depend on the exchange of physical matter.

Synchronized bioelectrical shifts in trees

The initial signs showed up in the baseline voltage levels. About half an hour before the eclipse reached its peak, all the trees being monitored began to show a clear change in electrical potential. The most noticeable shifts took place within a two-hour period surrounding the eclipse, with activity reaching its highest point near maximum coverage.

The voltage shifts measured between 30 and 90 millivolts, well beyond the usual changes linked to daily diurnal rhythms. These changes happened faster than the gradual patterns seen at sunrise or sunset. Analysis of the signal patterns, using tools like fast Fourier transforms and wavelet techniques, revealed a steady shift in spectral power, moving from mid to lower frequency ranges.

One of the key observations was the matching signal patterns across all trees. Even though they were spaced up to 50 m (164 feet) apart and had no direct connection, their electrical responses showed similar timing and shapes. Trees monitored outside the eclipse event did not show this kind of coordination.

Trees in Turin also showed voltage changes during the eclipse. The responses were less synchronized compared to those in Boves. Data from cloudy days, full overcast, and sunset periods showed no unusual electrical activity or coordination. This indicates that the effect was linked to the eclipse’s sudden environmental shift, not just reduced light. Also, there were no major temperature changes or wind patterns during the event. This made it unlikely that the electrical shifts were caused by physical stress, sap movement, or mechanical disturbance.

Another observation noted that older trees reacted earlier and more strongly to the eclipse. This may point to a kind of stored memory in older trees that helps them sense and respond to unusual events. The team suggests these older trees might even play a role in alerting younger ones. Monica Gagliano described the process as a glimpse into the so-called “wood wide web” at work.

Wavelet analysis and cross-correlation

Quantitative analysis using wavelet decomposition revealed that during the eclipse, the electrical signals showed higher amplitude in the low-frequency spectrum (~0.01–0.1 Hz), while mid-frequency components (0.1–0.5 Hz) diminished. This spectral shift was consistent across all nine trees under observation.

Cross-correlation analysis showed a clear rise in signal coherence between trees during the eclipse. The alignment reached up to 80%. This denotes that their electrical signals were rising and falling almost in sync. Outside eclipse periods, coherence stayed below 30%, showing that trees normally operate with more independent bioelectrical patterns. No electrical spikes, erratic signals, or noise artifacts were detected, ruling out technical interference. The recordings were stable and well within the operating parameters of the measurement system.

Possible mechanisms behind tree synchronization

The exact cause of the synchronization is still unclear. The researchers think it might involve light-sensitive signaling pathways. Trees have photoreceptors like phytochromes and cryptochromes that respond to shifts in light quality and duration, not just brightness. These receptors can affect how ions move across cell membranes, which in turn changes the tree’s electrical state.

The drop in light during an eclipse is much faster and involves a different light spectrum compared to normal day-night changes. This sudden shift may trigger a chain reaction in the tree’s vascular system, including changes in ion channel activity and shifts in membrane voltage.

Since trees lack a central nervous system, these signals are thought to move via the phloem or through cell-to-cell signaling using ion fluxes. The shared timing across different individuals suggests either a rapid response to the same external cue or a form of collective environmental sensing.

A new frontier in plant behavior research

The study offers a rare look at coordinated behavior in higher plants during a natural event. Animals often show synchronized responses during eclipses. For example, it has been observed that birds fall silent and insects stop moving. But this is one of the first times such bioelectrical coordination has been recorded in trees.

The findings open up new avenues for studying plant electrophysiology during changing environmental conditions. If trees can collectively respond to sudden shifts in sunlight, it might suggest common signaling pathways that help forests cope with environmental stress. This insight could be valuable for monitoring forest health or predicting how ecosystems will react to extreme climate events.

Professors Chiolerio and Gagliano and the team are still skeptical in their conclusions, saying that more data from future eclipses and other plant species will be needed to confirm the generality of the phenomenon.

Still, this study establishes the groundwork for viewing plant bioelectricity as an internal physiological signal that depicts a shared and responsive trait shaped by external conditions.

References:

¹ Forest in sync: spruce trees communicate during a solar eclipse – Southern Cross University – April 30, 2025

² Bioelectrical synchronization of Picea abies during a solar eclipse – Alessandro Chiolerio, Monica Gagliano, et al. – Royal Society Open Science – April 30, 2025 – DOI https://doi.org/10.1098/rsos.241786 – OPEN ACCESS

Harsh Vardhan

My passions include trying my best to save a dying planet, be it through carpooling or by spreading awareness about it. Research comes naturally to me, complemented by a keen interest in writing and journalism. Guided by a curious mind and a drive to look beyond the surface, I strive to bring thoughtful attention and clarity to subjects across Earth, sciences, environment, and everything in between.

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