Verspreiding van wegbermplanten in Oostelijk Flevoland

In Eastern Flevoland, a newly reclaimed IJssellake polder, the plant migration was studied along two roads (length 26 and 22 km). Along these roads which were built in the period 1958—’65, 66 plant species were found, 19 out of which belonged to the wild vegetation which established itself shortly after reclamation in 1957. These plants reached the new land by water (first migration phase) and by wind (second migration phase). In this study, these plants are called “early immigrants”. After the gradual reclamation of the land by man, a third migration took place. 37 species along the studied roads were disseminated in this last phase (group II, table 1). Most of these “late immigrants” are poorly disseminated by wind (table 2 and 3) and are mainly transported by man. There are quickly and slowly migrating species (fig. 2). A negative correlation was found between the number of late immigrants and the distance to the “old land” (fig. 3). The seeds of late immigrants are transported by man with the seedmixture used for the roadsides. More important is the transport of seeds caused by the traffic (a big difference was found in the number of late immigrants of the mainroad I and the secondary road Ia — table 4). It is evident that both accessibility and habitat selection play an important role in the floristic composition of the studied roadsides, as was confirmed by the results of a sowing experiment (table 5).