Physical Characterization of Seed Microsites -- Movement on the Ground

A dispersed seed must remain in a microsite long enough to imbibe water and germinate. Here the post-dispersal movement caused by wind of four asymmetric samaras of Picea engelmannii, P. abies, Pinus contorta var. latifolia and P. strobus was studied on four surface roughnesses (a smooth board, c. 250 μm, c. 750 μm and 2.0 mm). A mechanistic approach is taken to determine the chance that a seed will remain on a surface long enough to germinate. 2. The threshold or lift-off velocities for all combinations of four samaras and four surface roughnesses were determined in a wind tunnel