Mechanistic models of seed dispersal by wind

Ran Nathan*, Gabriel G. Katul, Gil Bohrer, Anna Kuparinen, Merel B. Soons, Sally E. Thompson, Ana Trakhtenbrot, Henry S. Horn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

166 Scopus citations

Abstract

Over the past century, various mechanistic models have been developed to estimate the magnitude of seed dispersal by wind, and to elucidate the relative importance of physical and biological factors affecting this passive transport process. The conceptual development has progressed from ballistic models, through models incorporating vertically variable mean horizontal windspeed and turbulent excursions, to models accounting for discrepancies between airflow and seed motion. Over hourly timescales, accounting for turbulent fluctuations in the vertical velocity component generally leads to a power-law dispersal kernel that is censored by an exponential cutoff far from the seed source. The parameters of this kernel vary with the flow field inside the canopy and the seed terminal velocity. Over the timescale of a dispersal season, with mean wind statistics derived from an "extreme-value" distribution, these distribution-tail effects are compounded by turbulent diffusion to yield seed dispersal distances that are two to three orders of magnitude longer than the corresponding ballistic models. These findings from analytic models engendered explicit simulations of the effects of turbulence on seed dispersal using computationally intensive fluid dynamics tools. This development marks a bifurcation in the approaches to wind dispersal, seeking either finer resolution of the dispersal mechanism at the scale of a single dispersal event, or mechanistically derived analytical dispersal kernels needed to resolve long-term and large-scale processes such as meta-population dynamics and range expansion. Because seed dispersal by wind is molded by processes operating over multiple scales, new insights will require novel theoretical tactics that blend these two approaches while preserving the key interactions across scales.

Original languageAmerican English
Pages (from-to)113-132
Number of pages20
JournalTheoretical Ecology
Volume4
Issue number2
DOIs
StatePublished - May 2011

Bibliographical note

Funding Information:
Acknowledgments We thank Simon Levin for his inspiration and guidance in wind dispersal modeling that gave rise thus far to five joint publications on wind dispersal models; we wish him happy birthday and further success in mentoring and research. Support for this study was available through grants from the Israel Science Foundation (ISF-474/02, ISF-150/07 and ISF-FIRST-1316/05), the US National Science Foundation (NSF-IBN-9981620, NSF-DEB-0453665), the International Arid Land Consortium (IALC 03R/25) the Ring Foundation, the Simon and Ethel Flegg Fellowship, and the Friedrich Wilhelm Bessel Research Award of the Humboldt Foundation to R. Nathan. G. Katul acknowledges support from NSF-EAR 0635787, NSF-ATM-0724088, the Bi-National Agricultural Research Development fund (BARD IS-3861-06), and the Fulbright-Italy Distinguished Fellows Program. G. Bohrer was funded by the USDA Forest Service Northern Research Station in Lansing MI (FS-NRS-06-Fire-10-01), USFS Northern Research Station in Delaware OH (09-CR-11242302-033), the Midwestern Regional Center of NICCR (DE-FC02-06ER64158), the US Department of Agriculture NIFA (2010-65112-20564) and NSF (NSF-DEB-0911461, NSF-DEB-0918869). A. Kuparinen acknowledges support from the Academy of Finland. M. B. Soons acknowledges support from the Netherlands Organization for Scientific research (NWO).

Keywords

  • Advection-diffusion models
  • Ballistic models
  • Canopy turbulence
  • Large-eddy simulations
  • Long-distance dispersal
  • WALD dispersal kernel

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