Seed dispersal capacity of six perennial grassland species measured in a wind tunnel at varying wind speed and height

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Abstract
The dispersal capacity of six perennial grassland species with different seed aerodynamic attributes was assessed in a wind tunnel. The selected species have difficulty in recolonizing restored ecosystems because of a poor dispersal of seeds. The variation in dispersal distances of seeds within and between species was assessed by releasing seeds at varying wind speeds and release heights, and expressed as 1st percentile, mode, and 99th percentile values. Dispersal distances of long-range dispersed seeds (99th percentile values) increased exponentially with wind speed. At wind speeds of 14 m/s, predicted maximum distances are 10–15 m for small and relatively heavy spherical seeds and 20–30 m for large and relatively light cylindrical or disk-like seeds. In the study area, wind gusts > 10 m/s at plant height occur at least annually, and plants of the selected species live up to several decades. This suggests a great potential for long-range dispersal during the lifetime of a plant. Plants may gain wider dispersal of seeds by increasing the release height (e.g., taller infructescences) and by requiring stronger winds to release seeds (e.g., dispersal in autumn and winter). Keywords: dispersal, wind tunnel, seeds, perennial, wind gust.