Assessing the effects of mowing machinery on seed dispersal pattern: a test of two methods of seed tracking

Seed dispersal is a key process that humans can influence in various ways. However, this type of interaction is less studied than dispersal by other animals. In addition, tracking seeds to determine dispersal pattern is a complicated task. We explored the effects of mowing machinery on seed dispersal in roadsides by testing two methods, (i) by marking fruits and diaspore of plants within the standing vegetation (ii) by making fake plants containing estimated quantities of marked seeds. We measured the pattern of dispersal by considering each seed and the centre of seed shadows of each species calculated by two means (i.e. the centroids and the gravity centres). We estimated the distance of dispersal from roadsides, and the deviation angle from the direction of the mowing. We then analysed the variation in dispersal patterns among species, seed mass and width/length ratio by using correlation tests. Seeds coloured within the standing vegetation were detected from 0.5 to 15.51 metres away from roadsides, with deviation angles from the mowing machinery ranging from –153.43° to 161.57°. With the other method we found a mean distance of dispersal ranging from 0.5 to 13.01 metres and deviation angle from –168.69° to 180°. We did not find strong variation in dispersal patterns among species and seed traits, but we demonstrated however that mowing machinery influenced both dispersal distance and deviation angles.