In the Dolomite mountains of Italy, something unusual happened in a spruce forest. It waited.

Not passively, like a crowd hushed before a performance, but with the poised expectancy of something alive and interconnected. Hours before the sky darkened in a partial solar eclipse, dozens of spruce trees began to shift. Their electrical pulses, imperceptible to human senses but measurable with the right instruments, started to align.

The forest, it turned out, had already sensed the eclipse coming.

A Pulse Beneath the Bark

It wasn’t sunlight that tipped the trees off. Nor temperature. Nor moisture. By the time the Moon even began to edge across the Sun, the trees had already changed. Their electrical signals — the biological hum that courses through every plant, a complex network of voltage shifts and ionic flows — grew more orderly and synchronized before and during the eclipse. Sensors embedded deep in trunks showed this rising tide of coherence that swept through the forest.

“Basically, we are watching the famous ‘wood wide web’ in action,” said Monica Gagliano, an evolutionary ecologist at Southern Cross University in Australia and one of the study’s lead authors.

That’s more than metaphor. Gagliano and her colleagues, including physicist Alessandro Chiolerio from the Italian Institute of Technology, used custom sensors — called “CyberTree” devices — to record the electrome of multiple spruce trees in real time. The electrome is the full range of electrical activity generated by a living organism’s cells and tissues, used to coordinate internal processes and respond to environmental changes.

Their goal was to capture what trees do during an eclipse. What they found is that trees don’t merely respond to the event. They seem to anticipate it.

And the elders know first.

The oldest trees in the forest — some over 70 years old — showed signs of anticipation well before their younger neighbors. Their electrical rhythms shifted earlier and more dramatically. In some cases, these shifts began nearly 14 hours before the eclipse even started.

To describe the forest’s behavior, the researchers used physics — quantum field theory to be more precise. In this context, the spruce forest acts as a “dissipative system” — a technical way of saying it constantly exchanges energy and matter with its environment.

“We now see the forest not as a mere collection of individuals, but as an orchestra of phase-correlated plants,” said Chiolerio.

That phrase — “orchestra of phase correlated plants” — isn’t just poetic. It’s grounded in data. The team measured how bioelectrical signals fluctuated across trees and compared those fluctuations to one another. During normal days, the trees’ signals bounced around with minimal coordination. During the eclipse, their signals fell into synchrony — sometimes rising, sometimes falling, but doing so together. It was a quiet, biological harmony.

And while the eclipse may have been the trigger, the synchronization started far too early for light or temperature to explain it. The team suspects another force: gravity.

Specifically, they point to lunisolar gravitational tides — minute but measurable forces exerted by the alignment of Earth, Moon, and Sun. The day of the eclipse saw a “perigee-syzygy” configuration: the Moon was at its closest point to Earth and aligned directly between us and the Sun. This arrangement happens regularly, in cycles trees may have experienced before.

If a tree has lived through several eclipses — perhaps separated by decades — could it somehow “remember” the pattern? Could it pass that memory along?

Gagliano thinks so. “The fact that older trees respond first — potentially guiding the collective response of the forest — speaks volumes about their role as memory banks of past environmental events,” she said.

The Strange Intelligence of Trees

This idea — that trees remember — is jarring. It pushes against our sense of intelligence as something quick, mobile, brain-bound. Trees are none of these. But slowness isn’t absence. It’s just a different timescale.

Gagliano is part of a growing movement of scientists exploring the sentience of plants — not in the anthropomorphic sense of “thinking,” but in their ability to sense, anticipate, and act in coordinated ways. Other studies have shown how plants respond to sound, detect kin, or adjust their behavior based on past experience. What sets this new study apart is its emphasis on collectivism.

Most plant studies focus on individuals. This one zooms out. It sees the forest.

And what it sees is a living network: trees communicating not through fungal threads or root systems, but through pulses of electricity. This kind of coordination has long been documented in animals — synchronous fireflies, murmuring starlings. In plants, it was largely unexplored until recently.

The researchers even found that electrical changes began subtly reshaping the forest’s energy use. Older trees — especially those bathed in sunlight — showed changes in the fractal dimension of their signals, a shift toward more orderly, less chaotic rhythms. After the eclipse, their signals returned to a noisier, more variable baseline. It was as if the forest had held its breath — then exhaled.

What We Lose When We Cut Down Trees

These findings land in a world where forests are burning, logged, and fragmented faster than ever. If old trees carry ecological memory — patterns of response shaped by decades of experience — then each felled elder is not just a loss of biomass. It’s a loss of knowledge.

“The discovery underscores the critical importance of protecting older forests,” said Gagliano, “which serve as pillars of ecosystem resilience by preserving and transmitting invaluable ecological knowledge.”

And perhaps they also serve as ‘teachers’. During the eclipse, the older trees changed first. The younger trees followed. This was not random. Cross-correlation analyses showed asymmetries — older trees seemed to lead the rhythm, not just join it.

This isn’t the first time plants have reacted to eclipses. Past research has shown drops in photosynthesis, slowed sap flow, disrupted stomatal rhythms. But those were individual reactions. This is the first evidence that trees might respond as a community. That a forest might have its own kind of memory.

The findings appeared in the Royal Society Open Science.