Explaining natural wonders: trees work in unison (Animals)

by David Turell , Wednesday, June 19, 2024, 18:36 (144 days ago) @ dhw

Controlled by responses to the sun:

https://www.quantamagazine.org/across-a-continent-trees-sync-their-fruiting-to-the-sun-...

"Each summer, like clockwork, millions of beech trees throughout Europe sync up, tuning their reproductive physiology to one another. Within a matter of days, the trees produce all the seeds they’ll make for the year, then release their fruit onto the forest floor to create a new generation and feed the surrounding ecosystem.

"It’s a reproductive spectacle known as masting that’s common to many tree species, but European beeches are unique in their ability to synchronize this behavior on a continental scale. From England to Sweden to Italy — across multiple seas, time zones and climates — somehow these trees “know” when to reproduce. But how?

A group of ecologists has now identified the distinctive cue — what they call the “celestial starting gun” — that, along with balmy weather, triggers the phenomenon. 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.

"It’s the first time scientists have linked masting to day length, though they still don’t know how the trees do it. “It is striking to find such a sharp change one day after the solstice. It doesn’t look random,” said Giorgio Vacchiano, a forest ecologist at the University of Milan who was not involved in the research.

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"Ecologists have floated various theories to explain the mysteries of masting. One idea is that, for wind-pollinated plants like beech trees, synchronized flower production improves pollination efficiency — the high, spreading plumes of pollen during masting produce more offspring. It may also be beneficial because masting trees go through periods of boom and bust, with high-masting, fruitful summers followed by low-masting, barren ones. (Researchers mostly agree that trees use low-masting years to store up resources for high-masting years.) Because of that variation, synchronized masting is likely to have value as a defense mechanism: Lean seed production in low-masting years can starve predators, and prolific production in high-masting years can overwhelm them.

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"Journé’s analysis suggested that European beech trees do mast in response to summer temperatures. But the twist is that they do not drop their seeds until they have sensed the longest day of the year. That combination of signals organizes the masting of the wide-flung beech trees into a compact period.

"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.”

"Bogdziewicz’s team took a novel approach by analyzing daily data: It’s rare for ecologists to track behavior at such a granular level, Vacchiano said. By recording incremental changes in response to daylight, the team showed that trees react to subtle external cues within an unexpectedly narrow window.

"It’s not surprising that trees synchronize their innate biological clocks with changes in light; most organisms do in some way. Species have evolved sensitivity to how much light is available in a 24-hour window, and that cue — the photoperiod — has been shown to influence a range of behaviors, from plant growth to hibernation, to migration, and to reproduction.

"The European beech is also not the first organism known to keep track of day length and the solstices. For example, long-distance migratory songbirds set their internal clocks to the photoperiod and use the summer solstice to time their nesting and migration, said Saeedeh Bani Assadi, a biologist at the University of Manitoba. Corals use day length to initiate spawning, but they prefer to reproduce under cover of darkness when the days are shortest, on the winter solstice.

Comment: with the seasonal changes caused by the Earth's tilt occurring regularly every year, it is not surprising to see the synchronization in nature, I assume by design.