Abstract
The seed shadow created by wind dispersal around parent trees may be affected by functional traits, as well as wind conditions and surrounding vegetation. This study of one mature tree each of 12 Neotropical species determined the extent to which species variation in diaspore traits vs. tree height and crop size explains (i) rate of diaspore descent in still air, (ii) distributions of diaspores dispersed from a 40-m tower in the forest, and (iii) natural seed shadows around the parent tree. A model of diaspore wing-loading to a fitted power explained 66·9% of the variation among species in the geometric mean rate of descent in still air. For a subset of four species, expected dispersal distance was not correlated with actual dispersal distance from the forest tower. For a subset of seven species, variation in wing-loading0·5 of individual diaspores explained ≤4·3% of the dispersal distance from the parent tree. Measured seed shadows, particularly their distribution edges and area, differed significantly among the 12 species (range in maximum tree height 19–42 m) and were best fit by 12 separate anisotropic dispersal kernels and surveyed fecundities. Measured mean distance was highly correlated with simulated distances from the kernels. The best models, explaining 57·6% of the variation among species in shadow area, and 59·6, 61·6 and 61·7% of variation in mean, median and maximum distances, included maximum tree height, either alone or in combination with crop size, and not diaspore rate of descent. Among 10 species, seed shadow area was not related to rank of seedling shade tolerance. In their highly skewed distributions, most seeds were much closer than the distance of greatest seedling recruitment and in very high density, thus enhancing later density- and/or distance-related seedling mortality. Tree functional traits, rather than the historically emphasized diaspore traits, explain distance distributions of these wind-dispersed species. Additional exploration of diaspore abscission in relation to wind and the influence of wind patterns after release are needed. A lay summary is available for this article.
| Original language | English |
|---|---|
| Pages (from-to) | 808-820 |
| Number of pages | 13 |
| Journal | Functional Ecology |
| Volume | 31 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 1 2017 |
| Externally published | Yes |
Funding
C.K.A. conceived of the project, collected data, contributed some data analysis and completed manuscript preparation; S.E.F. assisted with data collection and data analysis; and K.C.C. executed data analysis, fit dispersal kernel models, completed all model analyses, prepared figures and contributed to manuscript preparation. This research was supported by an NSF grant (BSR 8219856). The Smithsonian Tropical Research Institute (STRI) and the Krannert Center for the Performing Arts provided logistical support. H. Muller-Landau contributed advice in comparing dispersal kernels and building analytical models. We thank T. Beliz, A. Dominguez, B.A. Hursh, B. Hogan, M.R. Hogan, W.G. Hoppes, C.K. Kelly, M.D. Loveless and T. Wachter for field assistance, B. Hogan for drawing the seed shadows and J. O'Dwyer and anonymous reviewers for comments that improved the manuscript. The BCI forest dynamics research project was founded by S.P. Hubbell and R.B. Foster and is now managed by R. Condit, S. Lao and R. Perez under the Center for Tropical Forest Science and STRI. Numerous organizations have provided funding, principally the U.S. National Science Foundation, and hundreds of field workers have contributed. The authors declare no conflict of interests.
| Funders | Funder number |
|---|---|
| Center for Tropical Forest Science | |
| Krannert Center | |
| National Science Foundation | BSR 8219856 |
| Smithsonian Tropical Research Institute |
Keywords
- crop size
- dispersal kernel
- functional traits
- rate of descent
- seed shadow
- seedling recruitment
- tree height
- wing-loading