Modeling seed dispersal by wind in herbaceous species

Authored by E Jongejans, P Schippers

Date Published: 1999

DOI: 10.2307/3546752

Sponsors: No sponsors listed

Platforms: No platforms listed

Model Documentation: Other Narrative Mathematical description

Model Code URLs: Model code not found

Abstract

Wind can be regarded as the most important vector for seed dispersal in open grassland vegetation. Experimental estimates of seed dispersal distances in this environment are complex because of low arrival probabilities at large distances. Therefore, a proper mathematical generalization would be essential to give insight in dispersal probability distributions. Hence a promising individual-based model for seed dispersal presented by Andersen was tested for different wind velocities and seeds. Simulation results from the seed dispersal model were compared with observations in a horizontal wind tunnel. Considering the large variation in seed morphology and mass, the simulation results fitted wind tunnel results reasonably well, indicating the general applicability of the tested model for herbaceous species. Model sensitivity was evaluated with respect to wind speed and vegetation height. Differences in wind speed had a larger impact on the tail of the seed shadow than on median dispersal. However, vegetation height had little impact on the tail of the seed shadow compared to the median. Terminal velocity (V-t) is the crucial species specific parameter in wind dispersal models. There are two frequently used methods to determine V-t: a dropping method and a method to float seeds in an upward air stream. However, these methods have never been compared directly. This paper presents V-t values determined with both methods. In general results were in the same order. Only for high values of V-t the results of the floating method were found to be lower than the results of the dropping method. Simulation results showed that the intraspecific differences in V-t values were an important factor in determining the seed shadow.

Tags

morphology Capacity Plants Asteraceae Mass Fall Velocities Fertilizer Apparatus Diaspores