Take-off in anemochorus dispersal units of Carpinus betulus and Clematis vitalba: Observation in wind tunnel experiments and measurement of the basic force
Fonger, Patrick Pütz
published: Aug 5, 2002
Preliminary experiments on dispersal units of Carpinus betulus and Clematis vitalba were aimed at quantitative measurement of the basic forces involved in take-off. The measurements were completed using the spring scale principle. In Carpinus betulus, the take-off force measurements demonstrate that the basic force of take-off correlates to ripeness of dispersal unit. The values for basic force measured were shown to decrease over time, until a minimum take-off force of 0.2 N was finally reached. The force of dispersal unit take-off for Clematis vitalba was also found to be comparable. Several wind tunnel experiments were also carried out with this species. The parameters for take-off were turbulent wind flow and a wind velocity of 17 m/s. Moreover, C. vitalba shows individual adaptation under these conditions, with oscillating movements of the branches, and a complete 'shake off' of the dispersal units. It would appear that these take-off strategies, examples of which are described here, are important in the discussion of dispersal distances.