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Measuring the terminal velocity of tiny diaspores

Published online by Cambridge University Press:  08 July 2016

Gerhard Zotz*
Affiliation:
Functional Ecology of Plants, Institute of Biology and Environmental Sciences, University of Oldenburg, PO Box 2503, D-26111 Oldenburg, Germany Smithsonian Tropical Research Institute, Apdo 08343-03092, Panama, Republic of Panama
Tizian Weichgrebe
Affiliation:
Functional Ecology of Plants, Institute of Biology and Environmental Sciences, University of Oldenburg, PO Box 2503, D-26111 Oldenburg, Germany
Harry Happatz
Affiliation:
Technical-Scientific Infrastructure Unit, Electronics Department, University of Oldenburg, PO Box 2503, D-26111 Oldenburg, Germany
Helena J.R. Einzmann
Affiliation:
Functional Ecology of Plants, Institute of Biology and Environmental Sciences, University of Oldenburg, PO Box 2503, D-26111 Oldenburg, Germany
*
*Correspondence Fax: +49 441 7983331 Email: gerhard.zotz@uni-oldenburg.de

Abstract

Although it has long been acknowledged that seed characteristics are of major importance to the conquest of tree crowns by vascular epiphytes, there is surprisingly little quantitative evidence on the aerodynamic properties of their diaspores. We used a custom-built device to determine the terminal velocity (Vterm) of falling seeds, a parameter that has been shown to have high predictive power for the wind dispersal potential of diaspores under natural conditions. We determined Vterm of 45 species of epiphytic and terrestrial Orchidaceae, which almost doubles the currently available database for this family. Although varying by a factor of five with values of 0.09–0.4 m s−1, Vterm was invariably very slow compared to plants in general. For each species, we also took morphological data and determined seed mass. None of these parameters was linearly correlated with Vterm and neither did the average Vterm differ between species found in the two habitats, although seeds of terrestrial taxa were significantly larger and heavier. Finally, we demonstrate the potential of our device to measure Vterm of even smaller diaspores by successfully quantifying Vterm of fern spores. This tool has much potential for the quantitative study of dispersal of plants with tiny diaspores, particularly in a conservation context in fragmented landscapes.

Type
Research Papers
Copyright
Copyright © Cambridge University Press 2016 

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