Effects of agricultural practices on spatial dispersal patterns of four permanent grassland species

International audience; The effects of agricultural practices on floristic composition of grasslands are well known but few studies investigated these effects on plant spatial patterns involved in the maintenance of plant diversity. In order to identify major processes controlling dispersal patterns of four grassland species, presenting several dispersion modalities (anemochorous, barochorous and zoochorous sensu Grime et al., 1988), we have used spatial analysis (4TLQV and Wavelet)adapted to grids sampling. With these methods, when the quadrat variances are plotted against block size, the peaks of these graphs are interpreted as the scale of the mapped phenomena (Guo and Kelly, 2004). A generalization of mowing impact according to dispersal modalities was highlighted by our results. Indeed, an effect of mowing on spatial patterns from functional traits connected to dispersion was showed by spatial analysis. For example, dispersal distances of barochorous species such as Ranunculus bulbosus is enhanced by mowing and grazing. In contrast, zoochorous grass (Festuca arundinacea) which have the theoretical capacities to produce expansive lateral spread up to 1 meter was limited in his expansion by cutting and grazing. This study showed that disturbance can play an important role in dispersal and the spatial structure of grasslands species.