Across a Continent, Trees Sync Their Fruiting to the Sun | Quanta Magazine

Highlights

European beech trees more than 1,500 kilometers apart all drop their fruit at the same time in a grand synchronization event now linked to the summer solstice.

From England to Sweden to Italy — across multiple seas, time zones and climates — somehow these trees “know” when to reproduce. But how?

Their analysis of over 60 years’ worth of seeding data suggests that European beech trees time their masting to the summer solstice and peak daylight.

The discovery of the genetic mechanism that governs this solstice-monitoring behavior could bring researchers closer to understanding many other mysteries of tree physiology.

So it’s easy to see why masting trees synchronize their seed production. Understanding how they do it, however, is more complicated. Plants usually synchronize their reproduction by timing it to the same weather signals.

Then the team stumbled across a clue by accident. One summer evening, Bogdziewicz was sitting on his balcony reading a study which found that the timing of leaf senescence — the natural aging process leaves go through each autumn — depends on when the local weather warms relative to the summer solstice. Inspired by this finding, he sent the paper to his research group and called a brainstorming session.

It’s the first time that researchers have identified day length as a cue for masting. While Koenig cautioned that the result is only correlational, he added that “there’s very little out there speculating on how the trees are doing what they’re doing.”

If the solstice is shown to activate a genetic mechanism, it would be a major breakthrough for the field. Currently, there’s little data to explain how trees behave as they do. No one even knows whether trees naturally grow old and die, Vacchiano said. Ecologists struggle just to study trees: From branches to root systems, the parts of a tree say very little about the physiology of the tree as a whole. What experts do know is that discovering how trees sense their environment will help them answer the questions that have been stumping them for decades.