Floating times of riparian seeds

Posted on March 27, 2017

Given the important role that the transport of water-borne seeds plays in the long-distance dispersal of riparian plants, surprisingly little is known about this process.   In laboratory experiments, a team of Australian and Chinese scientists measured the floating times of seeds collected from sixty species of Australian riparian plant species. Most species reached the test criterion (90% of seeds sunk) within two days.   The strongest predictor of seed floating times was dispersal category, with water/wind-dispersed seeds being the best floaters and ant-dispersed seeds the fastest sinkers. Seeds with long floating times tended to be small and non-spherical, with a low density, and in many such cases, appendages such as wings and hooks on the seeds contributed to their low volume : surface area ratio. The researchers used their data to develop a model describing how seed traits interact with surface tension, buoyancy and flow velocity to determine floating time. The model covers a range of seed types and helps to link seed traits to patterns of riparian species composition.

Reference: Carthey, A.J.R. et al. 2016. How seed traits predict floating times: a biophysical process model for hydrochorous seed transport behaviour in fluvial systems.   Freshwater Biology 61, 19–31. http://onlinelibrary.wiley.com/doi/10.1111/fwb.12672/epdf