Spatial concordance between seed rain and seedling establishment in bird-dispersed trees: does scale matter?
Daniel García (fax +34 985 104866; e-mail: firstname.lastname@example.org).
- 1We explored whether seedling recruitment was spatially predicted by seed rain (spatial concordance) at different scales (microsite, microhabitat and site) in the bird-dispersed trees Crataegus monogyna, Ilex aquifolium and Taxus baccata, in temperate secondary forests in north-west Spain.
- 2We propose that both spatial concordance within each scale and consistency of concordance patterns across scales are dependent on differences between seed rain and post-dispersal processes in the partitioning of spatial variance at each scale.
- 3We measured the density of dispersed seeds, the percentage of post-dispersal seed predation by rodents and the density of emerged first-year seedlings at sampling stations distributed throughout five microhabitats (under canopies of parental trees and in open gaps) and four localities over two seasons.
- 4Seed rain density of all tree species varied most at the microhabitat scale, but microsite and site differences accounted for most of the spatial variance in post-dispersal seed predation and, especially, in seedling establishment.
- 5All three species showed concordance between seed rain and seedling establishment at the microhabitat scale, because strong patchiness in avian-generated seed rain overrode the slight uncoupling effects exerted by the more homogeneous post-dispersal processes. Seed rain was also a good predictor of recruitment of Ilex and Crataegus at the microsite scale, but, for Taxus, the rather homogeneous dispersal across microsites contrasted with the heterogeneous post-dispersal losses. At the site scale, only Taxus showed a positive trend of concordance.
- 6Concordance patterns were maintained from microsite to microhabitat in Crataegus and Ilex, and from microhabitat to site in Taxus. Low-variance allocation to the site scale at the seed rain stage precluded complete consistency in Crataegus and Ilex.
- 7Positive responses of recruitment to seed dispersal depended on both species and scale, resulting in a complex template for dispersal-limitation effects on metapopulations and communities.