Study

Mechanisms of long-distance dispersal of seeds by wind

Nathan, Ran; Katul, Gabriel G.; Horn, Henry S.; Thomas, Suvi M.; Oren, Ram; Avissar, Roni; Levin, Simon A.

Nature, 2002

Peer-reviewedmodelling studywild

What they did

Seed release timing, terminal velocity and canopy turbulence were measured in a forest and coupled to a model of atmospheric transport, to identify what actually produces the rare long-distance dispersal events that matter for colonisation.

Studied in: Pinus taeda, Liriodendron tulipifera
Sample size: seed release and turbulence measurements coupled to a dispersal model

What they found

Long-distance dispersal is dominated by rare updraught events that lift seeds above the forest canopy. Whether a seed travels metres or kilometres depends far more on the turbulence at the moment of release than on the seed’s own aerodynamics.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

Uplift by canopy turbulence, not seed morphology, governs the tail of the wind dispersal distribution.

How NatureHQ reads it

This overturns the intuitive picture in a way that matters. It is natural to assume a better-designed seed travels further, and for typical distances that holds; the rare journeys that let a species cross a valley or recolonise after a fire are governed by weather, not by wing shape. It also explains why dispersal distances are so hard to measure — the events that count are the ones you almost never observe.

Limitations

Two tree species in one forest type, coupled to a model rather than tracked seeds.
Long-distance events are by definition rarely observed directly.
Does not address animal-mediated long-distance dispersal, which can exceed wind.