Foliage shedding in deciduous forests lifts up long-distance seed dispersal by wind.

Journal Article

Seed terminal velocity and release height are recognized as key biotic determinants of long-distance dispersal (LDD) of seeds by wind. Yet, potential determinants at the ecosystem level, such as seasonal dynamics in foliage density characterizing many deciduous forests, have received much less attention. We integrated detailed field observations and experiments with a mechanistic wind dispersal model to assess how seasonal variation in foliage density, estimated by leaf-area index (LAI), affects LDD in deciduous forests. We found that the model, previously shown to accurately predict seed dispersal by wind, also reliably describes the effects of LAI variation on wind statistics for a wide range of canopy types. Sparser canopies are characterized by more organized vertical eddy motion that promotes LDD by uplifting seeds to higher elevations where winds are stronger. Yet, sparser canopies are also characterized by reduced mean windspeed aloft. We showed that former effect more than compensates for the latter, i.e., conditions of low LAI are favorable for LDD. This may account for the tendency of many temperate tree species to restrict seed release to either early spring or late fall, when LAI is relatively low. Sensitivity analysis reveals that the typical seasonal variation in LAI can be more important to LDD of seeds by wind than the natural variation in seed terminal velocity. Because our model accurately describes the effects of LAI variation for distinctly different sites, species, and life forms, we suggest that its results reflect a general association between LDD and foliage density dynamics.

Full Text

Duke Authors

Cited Authors

  • Nathan, R; Katul, GG

Published Date

  • June 7, 2005

Published In

Volume / Issue

  • 102 / 23

Start / End Page

  • 8251 - 8256

PubMed ID

  • 15928094

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.0503048102

Language

  • eng

Conference Location

  • United States